Timer: Off
Random: Off
201. Which of the following alkaline earth metals has the highest polarization tendency?
ⓐ. Magnesium (Mg)
ⓑ. Calcium (Ca)
ⓒ. Barium (Ba)
ⓓ. Strontium (Sr)
Correct Answer: Magnesium (Mg)
Explanation: Magnesium (Mg) has the highest polarization tendency among the alkaline earth metals. This is due to its smaller ionic size and higher charge density compared to the other alkaline earth metals. The higher the charge density, the more easily the metal cation can polarize the electron cloud of the anion, resulting in a greater polarization tendency.
202. What is the effect of high polarization on the bonding behavior of alkaline earth metals?
ⓐ. It promotes the formation of ionic bonds
ⓑ. It leads to the formation of superoxides
ⓒ. It decreases the reactivity of the metal
ⓓ. It leads to the formation of covalent bonds
Correct Answer: It leads to the formation of covalent bonds
Explanation: High polarization tendency in alkaline earth metals leads to the formation of covalent bonds. The small ionic size and high charge density of these metals, such as magnesium, make it easier for them to distort the electron cloud of the anion, promoting covalent bonding rather than purely ionic bonding.
203. Which of the following is a typical property of compounds formed by alkaline earth metals with high polarization tendency?
ⓐ. They are ionic and highly soluble in water
ⓑ. They form highly volatile compounds
ⓒ. They form basic oxides only
ⓓ. They are covalent and less soluble in water
Correct Answer: They are covalent and less soluble in water
Explanation: Compounds formed by alkaline earth metals with high polarization tendency, such as magnesium chloride ($MgCl_2$), are typically covalent in nature. These compounds tend to have lower solubility in water compared to more ionic compounds formed by heavier metals in the group.
204. Which of the following reactions demonstrates the formation of a covalent compound by an alkaline earth metal?
ⓐ. $Ca + Cl_2 \rightarrow CaCl_2$
ⓑ. $Be + Cl_2 \rightarrow BeCl_2$
ⓒ. $Mg + H_2O \rightarrow Mg(OH)_2 + H_2$
ⓓ. $Ba + Cl_2 \rightarrow BaCl_2$
Correct Answer: $Be + Cl_2 \rightarrow BeCl_2$
Explanation: The reaction $Be + Cl_2 \rightarrow BeCl_2$ demonstrates the formation of a covalent compound. Beryllium (Be) forms covalent bonds with chlorine due to its high polarization tendency and smaller ionic size. This is in contrast to heavier alkaline earth metals, which form more ionic compounds.
205. Why does beryllium (Be) form covalent compounds while other alkaline earth metals form ionic compounds?
ⓐ. Beryllium has a larger ionic size
ⓑ. Beryllium has a lower charge density
ⓒ. Beryllium has a higher ionization energy and smaller ionic size
ⓓ. Beryllium reacts more vigorously with non-metals
Correct Answer: Beryllium has a higher ionization energy and smaller ionic size
Explanation: Beryllium (Be) forms covalent compounds because it has a higher ionization energy and smaller ionic size compared to other alkaline earth metals. These factors lead to greater polarization of the anion, which promotes covalent bonding, unlike the larger cations of other alkaline earth metals that form ionic bonds.
206. Which of the following compounds formed by alkaline earth metals is typically covalent in nature?
ⓐ. $BeCl_2$
ⓑ. $CaO$
ⓒ. $MgO$
ⓓ. $BaSO_4$
Correct Answer: $BeCl_2$
Explanation: Beryllium chloride ($BeCl_2$) is typically covalent in nature due to the high polarization tendency of beryllium ($Be^{2+}$). Beryllium’s small size and high charge density make it more likely to form covalent bonds with chlorine, in contrast to other alkaline earth metals that form ionic compounds.
207. What effect does high polarization tendency have on the solubility of compounds formed by alkaline earth metals?
ⓐ. Compounds with high polarization tendency are more soluble in polar solvents
ⓑ. Compounds with high polarization tendency are less soluble in polar solvents
ⓒ. Polarization tendency does not affect solubility
ⓓ. High polarization increases the melting point
Correct Answer: Compounds with high polarization tendency are less soluble in polar solvents
Explanation: Compounds with high polarization tendency, such as $BeCl_2$ and $BeO$, are generally less soluble in polar solvents like water. The covalent nature of these compounds reduces their ability to dissociate in polar solvents, which is in contrast to more ionic compounds formed by heavier alkaline earth metals.
208. What is the primary reason for magnesium (Mg) forming covalent compounds with non-metals?
ⓐ. Magnesium has a high charge density and small ionic radius
ⓑ. Magnesium has a low ionization energy
ⓒ. Magnesium forms ionic compounds only
ⓓ. Magnesium reacts slowly with non-metals
Correct Answer: Magnesium has a high charge density and small ionic radius
Explanation: Magnesium (Mg) has a high charge density and small ionic radius, which allows it to form covalent compounds with non-metals. The small size of the $Mg^{2+}$ ion leads to greater polarization of the electron cloud of the anion, promoting covalent bonding.
209. Which of the following is the typical behavior of calcium (Ca) when it reacts with halogens?
ⓐ. Calcium forms only ionic compounds
ⓑ. Calcium forms covalent bonds exclusively
ⓒ. Calcium forms covalent and ionic compounds depending on the halogen
ⓓ. Calcium does not react with halogens
Correct Answer: Calcium forms only ionic compounds
Explanation: Calcium (Ca) is a reactive Group 2 metal and halogens are reactive Group 17 non-metals; the large electronegativity difference means they form classic ionic bonds (e.g., $CaF_2$, $CaCl_2$).
210. What happens when magnesium (Mg) reacts with chlorine (Cl₂)?
ⓐ. Magnesium forms a covalent chloride ($MgCl_2$)
ⓑ. Magnesium forms magnesium hydroxide ($Mg(OH)_2$)
ⓒ. Magnesium forms magnesium oxide ($MgO$)
ⓓ. Magnesium forms an ionic chloride ($MgCl_2$)
Correct Answer: Magnesium forms an ionic chloride ($MgCl_2$)
Explanation: When magnesium (Mg) reacts with chlorine (Cl₂), it forms magnesium chloride ($MgCl_2$), which is an ionic compound. Magnesium loses two electrons to form $Mg^{2+}$ ions, while chlorine gains those electrons to form $Cl^-$ ions, resulting in the ionic compound $MgCl_2$.
211. Which of the following methods is used for the industrial preparation of sodium chloride (NaCl)?
ⓐ. Electrolysis of sodium hydroxide solution
ⓑ. Reaction of sodium metal with chlorine gas
ⓒ. Mining of rock salt
ⓓ. Reaction of sodium bicarbonate with hydrochloric acid
Correct Answer: Mining of rock salt
Explanation: Sodium chloride (NaCl) is primarily obtained by mining rock salt from underground salt deposits. It can also be obtained from seawater by evaporation or by reacting sodium metal with chlorine gas, but mining is the most common industrial method.
212. What is the main property of sodium chloride (NaCl) in its solid state?
ⓐ. It is a non-conductor of electricity
ⓑ. It is a good conductor of electricity
ⓒ. It forms a covalent bond
ⓓ. It is soluble in non-polar solvents
Correct Answer: It is a non-conductor of electricity
Explanation: Sodium chloride (NaCl) in its solid state does not conduct electricity because the ions are fixed in the crystal lattice and cannot move. However, when NaCl is dissolved in water or melted, it becomes an excellent conductor of electricity due to the free movement of ions.
213. Which of the following is a primary use of sodium chloride (NaCl) in the chemical industry?
ⓐ. Production of chlorine gas and sodium hydroxide
ⓑ. Manufacture of sodium bicarbonate
ⓒ. Production of ammonia
ⓓ. Manufacture of sulfuric acid
Correct Answer: Production of chlorine gas and sodium hydroxide
Explanation: Sodium chloride (NaCl) is commonly used in the chlor-alkali process to produce chlorine gas ($Cl_2$) and sodium hydroxide ($NaOH$). This process involves the electrolysis of aqueous sodium chloride and is a key method for producing chlorine and sodium hydroxide, both of which have important industrial uses.
214. What is the solubility of sodium chloride (NaCl) in water at room temperature?
ⓐ. Very low solubility
ⓑ. Moderately soluble
ⓒ. Insoluble
ⓓ. Highly soluble
Correct Answer: Highly soluble
Explanation: Sodium chloride (NaCl) is highly soluble in water at room temperature. The ionic nature of NaCl allows it to dissociate into sodium ($Na^+$) and chloride ($Cl^-$) ions, which are easily solvated by water molecules, making NaCl highly soluble.
215. What is the crystal structure of sodium chloride (NaCl)?
ⓐ. Tetragonal
ⓑ. Orthorhombic
ⓒ. Face-centered cubic
ⓓ. Hexagonal
Correct Answer: Face-centered cubic
Explanation: Sodium chloride (NaCl) crystallizes in a face-centered cubic (FCC) lattice structure. In this structure, each sodium ion is surrounded by six chloride ions and each chloride ion is surrounded by six sodium ions, forming a highly stable and symmetrical crystal structure.
216. Which of the following properties is characteristic of sodium chloride (NaCl)?
ⓐ. It is highly volatile at room temperature
ⓑ. It is insoluble in water
ⓒ. It is an organic compound
ⓓ. It has a high melting point
Correct Answer: It has a high melting point
Explanation: Sodium chloride (NaCl) has a high melting point due to the strong electrostatic forces between the sodium and chloride ions in its crystal lattice. These ionic bonds require a significant amount of energy to break, resulting in a high melting point.
217. Sodium chloride (NaCl) is commonly used in which of the following applications?
ⓐ. De-icing roads in winter
ⓑ. Manufacturing of soap
ⓒ. As a food preservative in alcoholic beverages
ⓓ. As a solvent for organic compounds
Correct Answer: De-icing roads in winter
Explanation: Sodium chloride (NaCl) is widely used for de-icing roads in winter. It lowers the freezing point of water, preventing ice formation and helping to clear snow and ice from roads. NaCl is also used in food preservation, but de-icing is one of its most common applications in colder climates.
218. How does sodium chloride (NaCl) behave when dissolved in water?
ⓐ. It dissociates into sodium and chloride ions
ⓑ. It forms a colloidal solution
ⓒ. It forms a suspension in water
ⓓ. It remains undissolved
Correct Answer: It dissociates into sodium and chloride ions
Explanation: When sodium chloride (NaCl) dissolves in water, it dissociates into sodium ions ($Na^+$) and chloride ions ($Cl^-$). The ions are surrounded by water molecules, making the solution electrically conductive.
219. What is the role of sodium chloride (NaCl) in the human body?
ⓐ. It helps in the formation of bones and teeth
ⓑ. It regulates the balance of fluids and electrolytes
ⓒ. It is involved in the digestion of proteins
ⓓ. It contributes to the formation of hemoglobin
Correct Answer: It regulates the balance of fluids and electrolytes
Explanation: Sodium chloride (NaCl) plays a crucial role in regulating the balance of fluids and electrolytes in the human body. Sodium ions ($Na^+$) are essential for maintaining osmotic balance, nerve function, and muscle contraction. Chloride ions ($Cl^-$) also help maintain the body’s electrolyte balance.
220. What is the byproduct formed when sodium chloride (NaCl) undergoes electrolysis?
ⓐ. Hydrogen gas ($H_2$) and oxygen gas ($O_2$)
ⓑ. Sodium metal and oxygen gas ($O_2$)
ⓒ. Sodium peroxide ($Na_2O_2$) and hydrogen gas ($H_2$)
ⓓ. Chlorine gas ($Cl_2$) and sodium hydroxide ($NaOH$)
Correct Answer: Chlorine gas ($Cl_2$) and sodium hydroxide ($NaOH$)
Explanation: When sodium chloride (NaCl) undergoes electrolysis, chlorine gas ($Cl_2$) is produced at the anode and sodium hydroxide ($NaOH$) is produced at the cathode. This process is known as the chlor-alkali process and is used in the industrial production of chlorine and sodium hydroxide.
221. Which of the following is the primary method used to manufacture sodium carbonate (Na₂CO₃), also known as soda ash?
ⓐ. Contact process
ⓑ. Solvay process
ⓒ. Haber process
ⓓ. Ostwald process
Correct Answer: Solvay process
Explanation: The primary method used to manufacture sodium carbonate (Na₂CO₃) is the Solvay process. In this process, calcium carbonate ($CaCO_3$) reacts with sodium chloride ($NaCl$) and ammonia ($NH_3$) in the presence of water to produce sodium carbonate, calcium hydroxide, and ammonium chloride.
222. Which of the following is a major component in the production of sodium carbonate using the Solvay process?
ⓐ. Calcium sulfate ($CaSO_4$)
ⓑ. Ammonium chloride ($NH_4Cl$)
ⓒ. Sodium chloride ($NaCl$)
ⓓ. Sodium bicarbonate ($NaHCO_3$)
Correct Answer: Sodium bicarbonate ($NaHCO_3$)
Explanation: In the Solvay process, sodium bicarbonate ($NaHCO_3$) is precipitated out of the solution when carbon dioxide ($CO_2$) is bubbled through a mixture of ammonia ($NH_3$) and water, which reacts with sodium chloride ($NaCl$) and calcium carbonate ($CaCO_3$) to form sodium bicarbonate.
223. What is the byproduct of the Solvay process that is used in the treatment of wastewater?
ⓐ. Calcium carbonate ($CaCO_3$)
ⓑ. Calcium hydroxide ($Ca(OH)_2$)
ⓒ. Ammonium chloride ($NH_4Cl$)
ⓓ. Sodium hydroxide ($NaOH$)
Correct Answer: Ammonium chloride ($NH_4Cl$)
Explanation: Ammonium chloride ($NH_4Cl$) is a byproduct of the Solvay process. It can be treated and used in various applications, including the production of fertilizers and in wastewater treatment processes.
224. In the Solvay process, which of the following compounds is heated to release carbon dioxide gas ($CO_2$)?
ⓐ. Calcium carbonate ($CaCO_3$)
ⓑ. Sodium chloride ($NaCl$)
ⓒ. Calcium chloride ($CaCl_2$)
ⓓ. Ammonium bicarbonate ($NH_4HCO_3$)
Correct Answer: Calcium carbonate ($CaCO_3$)
Explanation: In the Solvay process, calcium carbonate ($CaCO_3$) is heated to produce calcium oxide ($CaO$) and carbon dioxide ($CO_2$). The carbon dioxide is then used to react with ammonia and sodium chloride to produce sodium bicarbonate, which is later converted to sodium carbonate.
225. What is the primary use of sodium carbonate (Na₂CO₃) in industry?
ⓐ. As a reducing agent in the chemical industry
ⓑ. As a solvent in the production of plastics
ⓒ. In the manufacture of glass
ⓓ. As a fuel in power plants
Correct Answer: In the manufacture of glass
Explanation: Sodium carbonate (Na₂CO₃), or soda ash, is primarily used in the manufacture of glass. It acts as a flux to lower the melting point of silica ($SiO_2$) and facilitates the formation of the glass structure. It is also used in detergent production, water treatment, and chemical synthesis.
226. Which of the following best describes the physical properties of sodium carbonate (Na₂CO₃)?
ⓐ. It is a colorless, odorless liquid
ⓑ. It is a white, crystalline solid
ⓒ. It is a yellow, non-crystalline powder
ⓓ. It is a green, crystalline solid
Correct Answer: It is a white, crystalline solid
Explanation: Sodium carbonate (Na₂CO₃) is a white, crystalline solid at room temperature. It is highly soluble in water and is typically used in powdered or granulated form in industrial applications like glass manufacturing and detergents.
227. What is the main environmental concern associated with the Solvay process?
ⓐ. Excessive production of carbon dioxide
ⓑ. High energy consumption
ⓒ. Release of toxic ammonia gas
ⓓ. Pollution of water sources with chlorine
Correct Answer: Excessive production of carbon dioxide
Explanation: The Solvay process produces carbon dioxide ($CO_2$) as a byproduct, which contributes to greenhouse gas emissions. While modern techniques aim to minimize environmental impact, the production of $CO_2$ remains a major concern for the process.
228. What happens when sodium carbonate (Na₂CO₃) is dissolved in water?
ⓐ. It forms a highly acidic solution
ⓑ. It forms a neutral solution
ⓒ. It forms a slightly alkaline solution
ⓓ. It forms a highly alkaline solution
Correct Answer: It forms a slightly alkaline solution
Explanation: Sodium carbonate (Na₂CO₃) dissolves in water to form a slightly alkaline solution due to the hydrolysis of the carbonate ions ($CO_3^{2-}$), which react with water to form bicarbonate ($HCO_3^-$) and hydroxide ($OH^-$) ions, increasing the pH of the solution.
229. What is the chemical equation for the reaction of sodium bicarbonate (NaHCO₃) with carbon dioxide ($CO_2$) in the Solvay process?
ⓐ. $NaHCO_3 + CO_2 \rightarrow Na_2CO_3 + H_2O$
ⓑ. $NaHCO_3 + CO_2 \rightarrow Na_2CO_3 + CO_2$
ⓒ. $NaHCO_3 + CO_2 \rightarrow NaHCO_3 + H_2O$
ⓓ. $NaHCO_3 + CO_2 \rightarrow Na_2CO_3 + O_2$
Correct Answer: $NaHCO_3 + CO_2 \rightarrow Na_2CO_3 + H_2O$
Explanation: In the Solvay process, sodium bicarbonate ($NaHCO_3$) reacts with carbon dioxide ($CO_2$) to form sodium carbonate ($Na_2CO_3$) and water ($H_2O$). This reaction occurs after the carbon dioxide is bubbled through the ammonia solution.
230. Which of the following statements about sodium carbonate (Na₂CO₃) is incorrect?
ⓐ. It is used in water softening to remove calcium ions
ⓑ. It is an essential ingredient in the production of soap
ⓒ. It is commonly used to neutralize acidic solutions
ⓓ. It is used primarily as a solvent in chemical reactions
Correct Answer: It is used primarily as a solvent in chemical reactions
Explanation: Sodium carbonate (Na₂CO₃) is not typically used as a solvent in chemical reactions. It is mainly used in industrial applications like water softening, glass manufacturing, and neutralizing acidic solutions, but not as a solvent.
231. Which of the following is the primary method used to prepare sodium bicarbonate (NaHCO₃), also known as baking soda?
ⓐ. Heating sodium carbonate (Na₂CO₃) with water
ⓑ. Reaction of sodium chloride (NaCl) with ammonia (NH₃)
ⓒ. Solvay process followed by reaction with carbon dioxide
ⓓ. Reaction of sodium carbonate (Na₂CO₃) with carbon dioxide (CO₂)
Correct Answer: Reaction of sodium carbonate (Na₂CO₃) with carbon dioxide (CO₂)
Explanation: Sodium bicarbonate (NaHCO₃) is commonly prepared by passing carbon dioxide ($CO_2$) through a solution of sodium carbonate ($Na_2CO_3$). The reaction forms sodium bicarbonate, which precipitates out of the solution and can be filtered, dried, and used in various applications, including baking.
232. What is the chemical formula of baking soda?
ⓐ. NaCl
ⓑ. Na₂CO₃
ⓒ. NaHCO₃
ⓓ. NaOH
Correct Answer: NaHCO₃
Explanation: The chemical formula for baking soda is sodium bicarbonate, $NaHCO_3$. It is a white crystalline compound commonly used in baking, as an antacid, and in cleaning applications.
233. What happens when sodium bicarbonate (NaHCO₃) is heated?
ⓐ. It decomposes to form sodium carbonate (Na₂CO₃), water, and carbon dioxide (CO₂)
ⓑ. It forms sodium oxide (Na₂O) and carbon dioxide (CO₂)
ⓒ. It forms sodium hydroxide (NaOH) and water
ⓓ. It reacts with oxygen to form sodium peroxide (Na₂O₂)
Correct Answer: It decomposes to form sodium carbonate (Na₂CO₃), water, and carbon dioxide (CO₂)
Explanation: When sodium bicarbonate (NaHCO₃) is heated, it decomposes to form sodium carbonate (Na₂CO₃), water (H₂O), and carbon dioxide (CO₂). This decomposition reaction is commonly used in baking, where the carbon dioxide produced helps dough rise.
234. Which of the following is a common use of sodium bicarbonate (NaHCO₃)?
ⓐ. As a disinfectant in medical applications
ⓑ. In the production of hydrogen gas
ⓒ. In baking as a leavening agent
ⓓ. In the production of soap
Correct Answer: In baking as a leavening agent
Explanation: Sodium bicarbonate (NaHCO₃), or baking soda, is commonly used as a leavening agent in baking. It reacts with acidic ingredients (such as vinegar or lemon juice) to release carbon dioxide gas, which helps dough rise and become light and fluffy.
235. What is the role of sodium bicarbonate (NaHCO₃) in the neutralization of acids?
ⓐ. It reacts with acids to form water and a salt
ⓑ. It reacts with acids to form a gas and water
ⓒ. It reacts with acids to form an alkaline solution
ⓓ. It does not react with acids
Correct Answer: It reacts with acids to form water and a salt
Explanation: Sodium bicarbonate (NaHCO₃) reacts with acids in a neutralization reaction to produce water and a salt. For example, when baking soda reacts with hydrochloric acid ($HCl$), it forms sodium chloride ($NaCl$), water ($H_2O$), and carbon dioxide ($CO_2$).
236. Which of the following reactions shows sodium bicarbonate (NaHCO₃) reacting with an acid?
ⓐ. $NaHCO_3 + H_2O \rightarrow NaOH + CO_2$
ⓑ. $NaHCO_3 + NaOH \rightarrow Na_2CO_3 + H_2O$
ⓒ. $NaHCO_3 + H_2SO_4 \rightarrow Na_2SO_4 + CO_2 + H_2O$
ⓓ. $NaHCO_3 + HCl \rightarrow NaCl + H_2O + CO_2$
Correct Answer: $NaHCO_3 + HCl \rightarrow NaCl + H_2O + CO_2$
Explanation: When sodium bicarbonate (NaHCO₃) reacts with hydrochloric acid (HCl), it forms sodium chloride (NaCl), water (H₂O), and carbon dioxide (CO₂). This reaction is an example of an acid-base reaction where the bicarbonate neutralizes the acid and releases gas.
237. Which of the following is the primary industrial use of sodium bicarbonate (NaHCO₃)?
ⓐ. In the production of detergents and soaps
ⓑ. As an antacid in medicine
ⓒ. In the manufacture of glass
ⓓ. In the neutralization of sulfuric acid
Correct Answer: As an antacid in medicine
Explanation: Sodium bicarbonate (NaHCO₃) is widely used as an antacid in medicine to neutralize stomach acid. It provides quick relief from indigestion and heartburn by reacting with excess hydrochloric acid in the stomach.
238. What is the effect of sodium bicarbonate (NaHCO₃) in water when used for cleaning?
ⓐ. It acts as a strong acid
ⓑ. It creates a highly alkaline solution
ⓒ. It forms an effervescent solution that helps remove stains
ⓓ. It reacts with minerals to form insoluble compounds
Correct Answer: It forms an effervescent solution that helps remove stains
Explanation: Sodium bicarbonate (NaHCO₃) in water forms an effervescent solution that helps lift stains and dirt. It reacts with acids and dirt particles, making it an effective, gentle cleaner for surfaces, fabrics, and even teeth.
239. What is the main product of the reaction between sodium bicarbonate (NaHCO₃) and vinegar (acetic acid, CH₃COOH)?
ⓐ. Sodium acetate ($CH_3COONa$) and carbon dioxide (CO₂)
ⓑ. Sodium hydroxide (NaOH) and carbon dioxide (CO₂)
ⓒ. Sodium chloride (NaCl) and water (H₂O)
ⓓ. Sodium carbonate (Na₂CO₃) and water (H₂O)
Correct Answer: Sodium acetate ($CH_3COONa$) and carbon dioxide (CO₂)
Explanation: When sodium bicarbonate (NaHCO₃) reacts with vinegar (acetic acid, CH₃COOH), it produces sodium acetate ($CH_3COONa$), carbon dioxide (CO₂), and water. This reaction is commonly used in household cleaning and as a leavening agent in baking.
240. Which of the following is an application of sodium bicarbonate (NaHCO₃) outside of the kitchen?
ⓐ. Used in toothpaste for whitening
ⓑ. Used in the preparation of fertilizers
ⓒ. Used in the production of glass
ⓓ. Used as a coolant in refrigeration systems
Correct Answer: Used in toothpaste for whitening
Explanation: Sodium bicarbonate (NaHCO₃) is commonly used in toothpaste for whitening and cleaning teeth. It is mildly abrasive and helps remove surface stains from teeth, making it an effective and natural ingredient in oral care products.
241. Which of the following methods is used for the industrial preparation of sodium hydroxide (NaOH)?
ⓐ. Solvay process
ⓑ. Contact process
ⓒ. Electrolysis of sodium chloride (NaCl)
ⓓ. Reaction of sodium bicarbonate (NaHCO₃) with acid
Correct Answer: Electrolysis of sodium chloride (NaCl)
Explanation: Sodium hydroxide (NaOH), or caustic soda, is primarily produced by the electrolysis of sodium chloride (NaCl) in water, a process known as the chlor-alkali process. This process produces sodium hydroxide at the cathode and chlorine gas ($Cl_2$) at the anode.
242. What is the primary product formed at the anode during the electrolysis of sodium chloride (NaCl) solution?
ⓐ. Hydrogen gas (H₂)
ⓑ. Oxygen gas (O₂)
ⓒ. Sodium hydroxide (NaOH)
ⓓ. Chlorine gas (Cl₂)
Correct Answer: Chlorine gas (Cl₂)
Explanation: During the electrolysis of sodium chloride (NaCl) solution, chlorine gas ($Cl_2$) is produced at the anode. Sodium hydroxide (NaOH) is formed at the cathode, and hydrogen gas (H₂) is also produced at the cathode in this process.
243. Which of the following is a property of sodium hydroxide (NaOH)?
ⓐ. It is highly acidic in nature
ⓑ. It is a strong base and highly caustic
ⓒ. It is insoluble in water
ⓓ. It is a weak base with low reactivity
Correct Answer: It is a strong base and highly caustic
Explanation: Sodium hydroxide (NaOH) is a strong base and is highly caustic, meaning it can cause severe chemical burns upon contact with skin. It is highly soluble in water and forms a strongly alkaline solution.
244. What is the chemical equation for the formation of sodium hydroxide (NaOH) from sodium chloride (NaCl) during electrolysis?
ⓐ. $2NaCl + 2H_2O \rightarrow 2NaOH + Cl_2 + H_2$
ⓑ. $NaCl + H_2O \rightarrow NaOH + Cl_2$
ⓒ. $2NaCl + H_2O \rightarrow NaOH + NaCl + H_2$
ⓓ. $NaCl + H_2O \rightarrow NaOH + H_2 + Cl_2$
Correct Answer: $2NaCl + 2H_2O \rightarrow 2NaOH + Cl_2 + H_2$
Explanation: The chemical equation for the electrolysis of sodium chloride (NaCl) solution shows that sodium hydroxide (NaOH) is formed along with chlorine gas ($Cl_2$) at the anode and hydrogen gas ($H_2$) at the cathode. This is the basis of the chlor-alkali process.
245. Which of the following is a major use of sodium hydroxide (NaOH)?
ⓐ. In the production of ammonia
ⓑ. As a cleaning agent and in soap making
ⓒ. In the manufacture of sulfuric acid
ⓓ. As a fuel in power plants
Correct Answer: As a cleaning agent and in soap making
Explanation: Sodium hydroxide (NaOH) is widely used as a cleaning agent, especially for removing grease, oils, and other residues. It is also an essential ingredient in the soap-making process, where it reacts with fats or oils to produce soap in a process called saponification.
246. What is the effect of sodium hydroxide (NaOH) on organic materials like fats and oils?
ⓐ. It forms an emulsion
ⓑ. It dissolves them completely
ⓒ. It causes them to break down into glycerol and fatty acids
ⓓ. It has no effect on organic materials
Correct Answer: It causes them to break down into glycerol and fatty acids
Explanation: Sodium hydroxide (NaOH) reacts with fats and oils in the process of saponification, breaking them down into glycerol (glycerin) and fatty acids, which then combine to form soap. This is a key step in soap-making.
247. Which of the following is the correct pH range of a solution of sodium hydroxide (NaOH)?
ⓐ. pH = 7
ⓑ. pH = 9–10
ⓒ. pH = 5–7
ⓓ. pH = 12–14
Correct Answer: pH = 12–14
Explanation: Sodium hydroxide (NaOH) is a strong base, and when dissolved in water, it results in a highly alkaline solution with a pH between 12 and 14. This high pH makes NaOH solutions strongly basic.
248. Sodium hydroxide (NaOH) is used in the production of which of the following products?
ⓐ. Hydrogen gas
ⓑ. Bleaching powder
ⓒ. Soap and detergent
ⓓ. Sulfuric acid
Correct Answer: Soap and detergent
Explanation: Sodium hydroxide (NaOH) is used in the production of soap and detergents. In the soap-making process, NaOH reacts with fats and oils in a process known as saponification to produce soap and glycerol.
249. Which of the following is a safety precaution when handling sodium hydroxide (NaOH)?
ⓐ. Always use it in a well-ventilated area
ⓑ. Avoid direct contact with skin, as it is caustic
ⓒ. Always store it in a plastic container
ⓓ. It can be handled without gloves and goggles
Correct Answer: Avoid direct contact with skin, as it is caustic
Explanation: Sodium hydroxide (NaOH) is highly caustic and can cause severe burns if it comes into contact with skin or eyes. Proper safety precautions, including the use of gloves, goggles, and proper ventilation, should always be followed when handling NaOH.
250. Sodium hydroxide (NaOH) is used in which of the following industries for neutralization purposes?
ⓐ. Paint and coating industry
ⓑ. Textile industry
ⓒ. Food industry (to neutralize acids)
ⓓ. Pharmaceutical industry (for the production of aspirin)
Correct Answer: Food industry (to neutralize acids)
Explanation: Sodium hydroxide (NaOH) is commonly used in the food industry to neutralize acids. It helps in controlling the pH of food products, such as in the production of soft drinks and other food processing tasks where acidity needs to be neutralized.
251. Which of the following is the primary method used to prepare calcium oxide (CaO), also known as quicklime?
ⓐ. Electrolysis of calcium chloride (CaCl₂)
ⓑ. Heating calcium carbonate (CaCO₃)
ⓒ. Reaction of calcium with oxygen
ⓓ. Heating calcium hydroxide (Ca(OH)₂)
Correct Answer: Heating calcium carbonate (CaCO₃)
Explanation: Calcium oxide (CaO), or quicklime, is primarily prepared by heating calcium carbonate (CaCO₃) in a kiln. This process, called calcination, decomposes calcium carbonate into calcium oxide and carbon dioxide gas ($CaCO_3 \xrightarrow{heat} CaO + CO_2$).
252. What is the primary use of calcium oxide (CaO) in the construction industry?
ⓐ. As a flux in the manufacture of glass
ⓑ. To remove sulfur impurities in steel production
ⓒ. In the production of calcium hydroxide (Ca(OH)₂)
ⓓ. As a component in cement and mortar
Correct Answer: As a component in cement and mortar
Explanation: Calcium oxide (CaO), also known as quicklime, is widely used in the construction industry as a key component in the production of cement and mortar. It reacts with water to form calcium hydroxide, which is an essential part of the chemical setting process in cement production.
253. What happens when calcium oxide (CaO) reacts with water?
ⓐ. It forms calcium carbonate (CaCO₃)
ⓑ. It forms calcium hydroxide (Ca(OH)₂)
ⓒ. It forms calcium peroxide (CaO₂)
ⓓ. It forms calcium hydroxide and hydrogen gas (H₂)
Correct Answer: It forms calcium hydroxide (Ca(OH)₂)
Explanation: When calcium oxide (CaO) reacts with water, it forms calcium hydroxide (Ca(OH)₂), a highly exothermic reaction. The reaction is as follows: $CaO + H_2O \rightarrow Ca(OH)_2$. This process is important in the production of slaked lime.
254. What is the chemical equation for the formation of calcium oxide (CaO) from calcium carbonate (CaCO₃)?
ⓐ. $CaCO_3 + H_2O \rightarrow CaO + CO_2$
ⓑ. $CaCO_3 \rightarrow CaO + O_2$
ⓒ. $CaCO_3 + 2H_2O \rightarrow Ca(OH)_2 + CO_2$
ⓓ. $CaCO_3 \xrightarrow{heat} CaO + CO_2$
Correct Answer: $CaCO_3 \xrightarrow{heat} CaO + CO_2$
Explanation: The chemical equation for the formation of calcium oxide (CaO) from calcium carbonate (CaCO₃) is: $CaCO_3 \xrightarrow{heat} CaO + CO_2$. This reaction occurs at high temperatures and is used in the production of quicklime in kilns.
255. Which of the following is a property of calcium oxide (CaO)?
ⓐ. It is highly soluble in water
ⓑ. It is a strong acid
ⓒ. It is a strong base
ⓓ. It is a neutral compound
Correct Answer: It is a strong base
Explanation: Calcium oxide (CaO) is a strong base. When it reacts with water, it forms calcium hydroxide ($Ca(OH)_2$), which is a strong base and is used to neutralize acids in various industrial applications.
256. Which of the following is a common industrial use of calcium oxide (CaO)?
ⓐ. As a reducing agent in metallurgy
ⓑ. In the manufacture of lime for the treatment of wastewater
ⓒ. In the production of sulfuric acid
ⓓ. In the production of glass and ceramics
Correct Answer: In the manufacture of lime for the treatment of wastewater
Explanation: Calcium oxide (CaO) is commonly used in the treatment of wastewater and in environmental applications. It is used to neutralize acids and remove impurities like phosphates and heavy metals from water, making it an important material in water treatment plants.
257. What happens when calcium oxide (CaO) is exposed to moist air?
ⓐ. It reacts with water to form calcium hydroxide
ⓑ. It forms calcium peroxide
ⓒ. It forms calcium carbonate
ⓓ. It remains unaffected
Correct Answer: It reacts with water to form calcium hydroxide
Explanation: When calcium oxide (CaO) is exposed to moist air, it reacts with water to form calcium hydroxide ($Ca(OH)_2$), a process known as slaking. The reaction is exothermic and produces heat: $CaO + H_2O \rightarrow Ca(OH)_2$.
258. Which of the following is the result of the reaction between calcium oxide (CaO) and carbon dioxide (CO₂)?
ⓐ. Calcium carbonate (CaCO₃)
ⓑ. Calcium hydroxide (Ca(OH)₂)
ⓒ. Calcium bicarbonate (Ca(HCO₃)₂)
ⓓ. Calcium peroxide (CaO₂)
Correct Answer: Calcium carbonate (CaCO₃)
Explanation: When calcium oxide (CaO) reacts with carbon dioxide (CO₂), it forms calcium carbonate ($CaCO_3$). This reaction is often used in the production of limestone and in carbon capture technologies: $CaO + CO_2 \rightarrow CaCO_3$.
259. Which of the following is a key use of calcium oxide (CaO) in the steel industry?
ⓐ. To increase the carbon content of steel
ⓑ. To remove sulfur impurities
ⓒ. To reduce the density of steel
ⓓ. To increase the iron content in steel
Correct Answer: To remove sulfur impurities
Explanation: Calcium oxide (CaO) is used in the steel industry to remove sulfur impurities. It reacts with sulfur to form calcium sulfide ($CaS$), which is then removed from the molten steel, improving the quality of the steel.
260. What is the byproduct of the reaction between calcium oxide (CaO) and carbon dioxide (CO₂) in the formation of calcium carbonate (CaCO₃)?
ⓐ. Oxygen (O₂)
ⓑ. Sulfur dioxide (SO₂)
ⓒ. Water (H₂O)
ⓓ. Carbon dioxide (CO₂)
Correct Answer: Carbon dioxide (CO₂)
Explanation: In the reaction between calcium oxide (CaO) and carbon dioxide (CO₂), the byproduct is calcium carbonate ($CaCO_3$). The reaction can be written as: $CaO + CO_2 \rightarrow CaCO_3$. No additional CO₂ is produced during this specific reaction, but CO₂ is essential for the formation of calcium carbonate.
261. Which of the following methods is used to prepare calcium hydroxide (Ca(OH)₂), also known as slaked lime?
ⓐ. Reaction of calcium oxide (CaO) with water
ⓑ. Electrolysis of calcium chloride (CaCl₂)
ⓒ. Reaction of calcium carbonate (CaCO₃) with carbon dioxide (CO₂)
ⓓ. Heating calcium bicarbonate (Ca(HCO₃)₂)
Correct Answer: Reaction of calcium oxide (CaO) with water
Explanation: Calcium hydroxide (Ca(OH)₂), or slaked lime, is prepared by adding water to calcium oxide (CaO), also known as quicklime. The reaction is exothermic and produces calcium hydroxide:
$CaO + H_2O \rightarrow Ca(OH)_2$.
262. What is the appearance of calcium hydroxide (Ca(OH)₂) in its solid form?
ⓐ. White powder
ⓑ. Greenish yellow powder
ⓒ. Colorless liquid
ⓓ. Yellowish crystalline solid
Correct Answer: White powder
Explanation: Calcium hydroxide (Ca(OH)₂), or slaked lime, appears as a white powder in its solid form. It is commonly used in water treatment, construction, and as a pH regulator.
263. Which of the following is a major use of calcium hydroxide (Ca(OH)₂)?
ⓐ. In the preparation of vinegar
ⓑ. In the production of steel
ⓒ. In the manufacture of ammonia
ⓓ. In the treatment of drinking water
Correct Answer: In the treatment of drinking water
Explanation: Calcium hydroxide (Ca(OH)₂) is widely used in the treatment of drinking water. It is used to neutralize acids, remove impurities, and clarify water by precipitating out substances like phosphate and fluoride.
264. What is the chemical equation for the reaction of calcium hydroxide (Ca(OH)₂) with carbon dioxide (CO₂)?
ⓐ. $Ca(OH)_2 + CO_2 \rightarrow CaCO_3 + H_2O$
ⓑ. $Ca(OH)_2 + CO_2 \rightarrow Ca(OH)_3CO_2$
ⓒ. $Ca(OH)_2 + CO_2 \rightarrow CaCO_3 + 2H_2O$
ⓓ. $Ca(OH)_2 + CO_2 \rightarrow Ca(HCO_3)_2$
Correct Answer: $Ca(OH)_2 + CO_2 \rightarrow CaCO_3 + H_2O$
Explanation: When calcium hydroxide (Ca(OH)₂) reacts with carbon dioxide (CO₂), calcium carbonate ($CaCO_3$) and water (H₂O) are formed. This reaction is commonly used to remove excess carbon dioxide in industrial processes and to precipitate calcium carbonate.
265. Which of the following is a property of calcium hydroxide (Ca(OH)₂) in its aqueous form (limewater)?
ⓐ. It is acidic in nature
ⓑ. It is neutral in nature
ⓒ. It does not affect litmus paper
ⓓ. It is a strong base and turns red litmus paper blue
Correct Answer: It is a strong base and turns red litmus paper blue
Explanation: Calcium hydroxide in its aqueous form, known as limewater, is a strong base. It turns red litmus paper blue due to its high pH and alkaline nature.
266. What happens when calcium hydroxide (Ca(OH)₂) is added to excess carbon dioxide (CO₂)?
ⓐ. It forms calcium bicarbonate (Ca(HCO₃)₂)
ⓑ. It forms calcium carbonate (CaCO₃)
ⓒ. It forms calcium peroxide (CaO₂)
ⓓ. It forms calcium hydroxide again
Correct Answer: It forms calcium bicarbonate (Ca(HCO₃)₂)
Explanation: When excess carbon dioxide (CO₂) is passed through calcium hydroxide (Ca(OH)₂) solution, calcium bicarbonate ($Ca(HCO_3)_2$) is formed. The reaction is as follows:
$Ca(OH)_2 + CO_2 \rightarrow Ca(HCO_3)_2$. This reaction is reversible and is used to demonstrate the solubility of calcium carbonate in excess CO₂.
267. Which of the following is an important industrial application of calcium hydroxide (Ca(OH)₂)?
ⓐ. As a reducing agent in metal extraction
ⓑ. In the preparation of hydrogen gas
ⓒ. In the neutralization of acidic soils
ⓓ. In the production of chlorine gas
Correct Answer: In the neutralization of acidic soils
Explanation: Calcium hydroxide (Ca(OH)₂) is used in agriculture to neutralize acidic soils. It helps raise the pH of the soil, making it more suitable for plant growth. This is commonly referred to as “liming” the soil.
268. How does calcium hydroxide (Ca(OH)₂) help in the removal of impurities from water?
ⓐ. It reacts with magnesium ions to form magnesium hydroxide
ⓑ. It reacts with chloride ions to form calcium chloride
ⓒ. It reacts with fluoride ions to form calcium fluoride
ⓓ. It reacts with sulfur compounds to form sulfur dioxide
Correct Answer: It reacts with fluoride ions to form calcium fluoride
Explanation: Calcium hydroxide (Ca(OH)₂) is used in water treatment to remove impurities such as fluoride ions. It reacts with fluoride ions to form calcium fluoride ($CaF_2$), which can then be removed from the water.
269. What happens when calcium hydroxide (Ca(OH)₂) is exposed to air?
ⓐ. It forms calcium carbonate (CaCO₃)
ⓑ. It forms calcium oxide (CaO)
ⓒ. It forms calcium hydroxide again
ⓓ. It remains unaffected
Correct Answer: It forms calcium carbonate (CaCO₃)
Explanation: When calcium hydroxide (Ca(OH)₂) is exposed to air, it absorbs carbon dioxide ($CO_2$) and forms calcium carbonate ($CaCO_3$). This reaction is used in the carbonation of lime in construction and water treatment:
$Ca(OH)_2 + CO_2 \rightarrow CaCO_3 + H_2O$.
270. Which of the following is a common use of calcium hydroxide (Ca(OH)₂) in the food industry?
ⓐ. To produce soft drinks
ⓑ. To clarify sugar syrup
ⓒ. To preserve vegetables
ⓓ. To manufacture chocolate
Correct Answer: To clarify sugar syrup
Explanation: Calcium hydroxide (Ca(OH)₂) is used in the food industry, particularly in the clarification of sugar syrup. It helps remove impurities and colorants from raw sugar by reacting with the dissolved substances and forming insoluble precipitates, which can be filtered out.
271. Which of the following is the main source of calcium carbonate (CaCO₃)?
ⓐ. Gypsum (CaSO₄)
ⓑ. Marble (CaCO₃)
ⓒ. Sodium carbonate (Na₂CO₃)
ⓓ. Calcium hydroxide (Ca(OH)₂)
Correct Answer: Marble (CaCO₃)
Explanation: Calcium carbonate (CaCO₃) is found naturally in limestone, chalk, and marble. These rocks are primarily composed of calcium carbonate, and they are mined for use in various industries such as construction, agriculture, and chemical production.
272. What is the chemical equation for the decomposition of calcium carbonate (CaCO₃) upon heating?
ⓐ. $CaCO_3 \xrightarrow{heat} CaO + CO_2$
ⓑ. $CaCO_3 \xrightarrow{heat} CaCO_3 + CO_2$
ⓒ. $CaCO_3 \xrightarrow{heat} CaO + C_2O_4$
ⓓ. $CaCO_3 + O_2 \rightarrow CaO + CO_2$
Correct Answer: $CaCO_3 \xrightarrow{heat} CaO + CO_2$
Explanation: When calcium carbonate (CaCO₃) is heated, it undergoes thermal decomposition to form calcium oxide (CaO) and carbon dioxide (CO₂). This reaction is commonly known as calcination:
$CaCO_3 \xrightarrow{heat} CaO + CO_2$.
273. What is the primary use of calcium carbonate (CaCO₃) in the construction industry?
ⓐ. To produce cement and concrete
ⓑ. As a binder in adhesives
ⓒ. As a flux in metal production
ⓓ. In the production of glass
Correct Answer: To produce cement and concrete
Explanation: Calcium carbonate (CaCO₃) is primarily used in the construction industry for the production of cement and concrete. When heated, calcium carbonate forms calcium oxide (CaO), which reacts with silica to form calcium silicate compounds used in cement manufacturing.
274. Which of the following is a property of calcium carbonate (CaCO₃)?
ⓐ. It is highly soluble in water
ⓑ. It decomposes upon heating to form a basic oxide
ⓒ. It is a non-reactive compound
ⓓ. It reacts with acids to release carbon dioxide
Correct Answer: It reacts with acids to release carbon dioxide
Explanation: Calcium carbonate (CaCO₃) reacts with acids, such as hydrochloric acid (HCl), to release carbon dioxide (CO₂) gas. This reaction is commonly used in laboratory experiments and in industry for producing carbon dioxide:
$CaCO_3 + 2HCl \rightarrow CaCl_2 + H_2O + CO_2$.
275. What is the effect of heating calcium carbonate (CaCO₃) at high temperatures?
ⓐ. It forms calcium chloride (CaCl₂)
ⓑ. It forms calcium oxide (CaO) and carbon dioxide (CO₂)
ⓒ. It forms calcium sulfate (CaSO₄)
ⓓ. It forms calcium hydroxide (Ca(OH)₂)
Correct Answer: It forms calcium oxide (CaO) and carbon dioxide (CO₂)
Explanation: When calcium carbonate (CaCO₃) is heated at high temperatures, it decomposes into calcium oxide (CaO) and carbon dioxide (CO₂). This process is the basis of the Solvay process and is used in lime production:
$CaCO_3 \xrightarrow{heat} CaO + CO_2$.
276. Which of the following is a common use of calcium carbonate (CaCO₃) in agriculture?
ⓐ. As a pesticide
ⓑ. To increase the soil temperature
ⓒ. As a plant growth promoter
ⓓ. To neutralize acidic soils
Correct Answer: To neutralize acidic soils
Explanation: Calcium carbonate (CaCO₃) is widely used in agriculture to neutralize acidic soils. It helps raise the pH of acidic soils, making them more suitable for plant growth by reducing soil acidity, a process known as liming.
277. What is the appearance of calcium carbonate (CaCO₃) in its pure form?
ⓐ. White crystalline solid
ⓑ. Greenish crystalline solid
ⓒ. Yellow powder
ⓓ. Colorless liquid
Correct Answer: White crystalline solid
Explanation: Calcium carbonate (CaCO₃) appears as a white crystalline solid in its pure form. It is commonly found in nature as limestone, chalk, and marble, all of which are composed primarily of calcium carbonate.
278. What is the primary component of marble?
ⓐ. Calcium sulfate (CaSO₄)
ⓑ. Calcium carbonate (CaCO₃)
ⓒ. Sodium chloride (NaCl)
ⓓ. Potassium chloride (KCl)
Correct Answer: Calcium carbonate (CaCO₃)
Explanation: Marble is primarily composed of calcium carbonate (CaCO₃). It is a metamorphic rock formed from the recrystallization of limestone under heat and pressure, and it is widely used in sculpture, construction, and decoration.
279. Which of the following reactions shows the formation of calcium carbonate (CaCO₃) from calcium oxide (CaO) and carbon dioxide (CO₂)?
ⓐ. $CaO + CO_2 \rightarrow Ca_2CO_3$
ⓑ. $CaO + CO_2 \rightarrow CaO_2$
ⓒ. $CaO + CO_2 \rightarrow CaCO_3$
ⓓ. $CaO + CO_2 \rightarrow CaO_3$
Correct Answer: $CaO + CO_2 \rightarrow CaCO_3$
Explanation: When calcium oxide (CaO) reacts with carbon dioxide (CO₂), it forms calcium carbonate (CaCO₃). This reaction is used in the production of limestone from quicklime (CaO):
$CaO + CO_2 \rightarrow CaCO_3$.
280. Which of the following is a common application of calcium carbonate (CaCO₃) in the pharmaceutical industry?
ⓐ. As a laxative and antacid
ⓑ. To produce hydrogen gas
ⓒ. To treat water hardness
ⓓ. As a preservative in food
Correct Answer: As a laxative and antacid
Explanation: Calcium carbonate (CaCO₃) is commonly used in the pharmaceutical industry as both a laxative and an antacid. It helps neutralize excess stomach acid and is also used to relieve indigestion and heartburn.
281. What is the primary method used to prepare Plaster of Paris (CaSO₄·½H₂O)?
ⓐ. Heating calcium carbonate (CaCO₃)
ⓑ. Electrolysis of calcium sulfate (CaSO₄)
ⓒ. Mixing calcium sulfate (CaSO₄) with water
ⓓ. Heating calcium sulfate dihydrate (CaSO₄·2H₂O)
Correct Answer: Heating calcium sulfate dihydrate (CaSO₄·2H₂O)
Explanation: Plaster of Paris (CaSO₄·½H₂O) is prepared by heating calcium sulfate dihydrate ($CaSO_4·2H_2O$) at about 150°C. This heating process drives off water molecules, resulting in the formation of Plaster of Paris:
$CaSO_4·2H_2O \xrightarrow{heat} CaSO_4·½H_2O + 1½H_2O$.
282. What is the chemical formula of Plaster of Paris?
ⓐ. CaSO₄·H₂O
ⓑ. CaSO₄·2H₂O
ⓒ. CaSO₄·½H₂O
ⓓ. CaCO₃·H₂O
Correct Answer: CaSO₄·½H₂O
Explanation: The chemical formula for Plaster of Paris is $CaSO_4·½H_2O$. It is a form of calcium sulfate that contains half a molecule of water per molecule of calcium sulfate.
283. What happens when Plaster of Paris (CaSO₄·½H₂O) is mixed with water?
ⓐ. It forms calcium carbonate (CaCO₃)
ⓑ. It dissolves completely in water
ⓒ. It forms a gel-like substance
ⓓ. It hardens to form a solid mass
Correct Answer: It hardens to form a solid mass
Explanation: When Plaster of Paris ($CaSO_4·½H_2O$) is mixed with water, it rehydrates to form calcium sulfate dihydrate ($CaSO_4·2H_2O$) and hardens to form a solid mass. This setting process is used for making molds, casts, and sculptures.
284. Which of the following is a common use of Plaster of Paris?
ⓐ. Making fertilizers
ⓑ. Making sculptures and molds
ⓒ. Producing cement
ⓓ. Water purification
Correct Answer: Making sculptures and molds
Explanation: Plaster of Paris is commonly used in the production of sculptures and molds due to its ability to set quickly and form a solid, durable structure. It is also used in medical casts and in the construction industry for decorative elements.
285. What happens to the setting time of Plaster of Paris if excess water is used?
ⓐ. The setting time decreases
ⓑ. The setting time remains unchanged
ⓒ. The setting time increases
ⓓ. The plaster hardens immediately
Correct Answer: The setting time increases
Explanation: If excess water is used when mixing Plaster of Paris with water, the setting time increases. This happens because the excess water dilutes the mixture, slowing down the hydration process and causing the plaster to set more slowly.
286. How does Plaster of Paris (CaSO₄·½H₂O) appear in its dry form?
ⓐ. White powder
ⓑ. Yellow crystals
ⓒ. Colorless liquid
ⓓ. Transparent solid
Correct Answer: White powder
Explanation: Plaster of Paris appears as a fine white powder in its dry form. When mixed with water, it rehydrates and hardens, forming a solid mass.
287. What is the main component of Plaster of Paris?
ⓐ. Calcium carbonate (CaCO₃)
ⓑ. Calcium sulfate (CaSO₄)
ⓒ. Calcium phosphate (Ca₃(PO₄)₂)
ⓓ. Calcium chloride (CaCl₂)
Correct Answer: Calcium sulfate (CaSO₄)
Explanation: The main component of Plaster of Paris is calcium sulfate ($CaSO_4$). Specifically, it is a hemihydrate form of calcium sulfate, with the chemical formula $CaSO_4·½H_2O$.
288. Which of the following reactions occurs when Plaster of Paris is mixed with water?
ⓐ. $CaSO_4·½H_2O + H_2O \rightarrow CaSO_4·2H_2O$
ⓑ. $CaSO_4·½H_2O + H_2O \rightarrow CaCO_3 + H_2O$
ⓒ. $CaSO_4·½H_2O + H_2O \rightarrow CaSO_3·2H_2O$
ⓓ. $CaSO_4·½H_2O + H_2O \rightarrow Ca(OH)_2 + SO_2$
Correct Answer: $CaSO_4·½H_2O + H_2O \rightarrow CaSO_4·2H_2O$
Explanation: When Plaster of Paris ($CaSO_4·½H_2O$) is mixed with water, it reacts to form calcium sulfate dihydrate ($CaSO_4·2H_2O$). This reaction is exothermic and causes the plaster to harden as it sets.
289. What is a key difference between Plaster of Paris and gypsum (CaSO₄·2H₂O)?
ⓐ. Plaster of Paris is more soluble in water than gypsum
ⓑ. Plaster of Paris contains twice as much water as gypsum
ⓒ. Gypsum is the hydrated form, while Plaster of Paris is the dehydrated form
ⓓ. Plaster of Paris is a weaker material than gypsum
Correct Answer: Gypsum is the hydrated form, while Plaster of Paris is the dehydrated form
Explanation: Gypsum ($CaSO_4·2H_2O$) is the hydrated form of calcium sulfate, while Plaster of Paris ($CaSO_4·½H_2O$) is the dehydrated form. Plaster of Paris is made by heating gypsum to remove water, and it can rehydrate to form gypsum again when mixed with water.
290. What is the primary use of Plaster of Paris in the medical field?
ⓐ. To make surgical instruments
ⓑ. To create orthopedic casts for broken bones
ⓒ. As a disinfectant in wound care
ⓓ. To treat infections
Correct Answer: To create orthopedic casts for broken bones
Explanation: Plaster of Paris is widely used in the medical field to create orthopedic casts for immobilizing broken bones. Its ability to harden quickly and form a durable, moldable structure makes it ideal for casting fractured limbs.
291. What is the primary ingredient in cement that provides its binding properties?
ⓐ. Calcium carbonate (CaCO₃)
ⓑ. Calcium sulfate (CaSO₄)
ⓒ. Magnesium oxide (MgO)
ⓓ. Calcium silicate (CaSiO₃)
Correct Answer: Calcium silicate (CaSiO₃)
Explanation: The primary ingredient in cement that provides its binding properties is calcium silicate ($CaSiO_3$). It is formed during the clinkerization process and plays a major role in the hardening and setting of cement.
292. Which of the following processes is used to manufacture cement?
ⓐ. Solvay process
ⓑ. Haber process
ⓒ. Portland cement process
ⓓ. Ostwald process
Correct Answer: Portland cement process
Explanation: The Portland cement process is the primary method used to manufacture cement. It involves heating a mixture of limestone ($CaCO_3$), clay, and other materials in a kiln to form clinker, which is then ground with gypsum to produce cement.
293. What is the role of gypsum (CaSO₄) in the manufacture of cement?
ⓐ. To increase the rate of hydration
ⓑ. To control the setting time of cement
ⓒ. To improve the tensile strength of cement
ⓓ. To reduce the production of carbon dioxide
Correct Answer: To control the setting time of cement
Explanation: Gypsum ($CaSO_4$) is added during the grinding of clinker to control the setting time of cement. It prevents the rapid setting of cement by inhibiting the premature formation of calcium aluminate hydrate, allowing for a more manageable setting time.
294. What is the chemical composition of Ordinary Portland Cement (OPC)?
ⓐ. 60-67% calcium silicate, 5-10% calcium aluminate
ⓑ. 30-40% calcium carbonate, 10-15% magnesium oxide
ⓒ. 40-50% calcium silicate, 10-15% calcium sulfate
ⓓ. 70-80% calcium silicate, 10-15% iron oxide
Correct Answer: 60-67% calcium silicate, 5-10% calcium aluminate
Explanation: Ordinary Portland Cement (OPC) is composed primarily of calcium silicate (60-67%), which provides its strength, and calcium aluminate (5-10%), which helps in the setting and early strength development of the cement.
295. What is the process of “hydration” in cement?
ⓐ. The drying process that removes moisture from the cement
ⓑ. The reaction between water and cement that leads to hardening
ⓒ. The process of grinding clinker with gypsum
ⓓ. The addition of water to cement to make it workable
Correct Answer: The reaction between water and cement that leads to hardening
Explanation: Hydration in cement refers to the chemical reaction between water and the cement particles, resulting in the formation of calcium silicate hydrate (C-S-H) gel, which binds the particles together and leads to hardening of the cement.
296. Which of the following materials is mixed with clinker to make cement?
ⓐ. Sand
ⓑ. Lime
ⓒ. Gypsum
ⓓ. Water
Correct Answer: Gypsum
Explanation: Gypsum ($CaSO_4$) is added to the clinker during the final grinding process to control the setting time of cement. Without gypsum, cement would set too quickly, making it difficult to handle and use.
297. What is the main product formed when cement hydrates with water?
ⓐ. Calcium hydroxide (Ca(OH)₂)
ⓑ. Calcium carbonate (CaCO₃)
ⓒ. Calcium silicate hydrate (C-S-H)
ⓓ. Calcium sulfate (CaSO₄)
Correct Answer: Calcium silicate hydrate (C-S-H)
Explanation: The main product formed when cement hydrates with water is calcium silicate hydrate (C-S-H), which is the primary compound responsible for the strength and hardening of cement. Calcium hydroxide (Ca(OH)₂) is also produced but is not responsible for strength.
298. In the setting of cement, which of the following compounds reacts first with water?
ⓐ. Calcium silicate
ⓑ. Calcium sulfate
ⓒ. Calcium hydroxide
ⓓ. Calcium aluminate
Correct Answer: Calcium aluminate
Explanation: In the setting of cement, calcium aluminate ($CaAl_2O_4$) reacts first with water, producing calcium aluminate hydrate (C-A-H), which contributes to the early strength development of the cement. Calcium silicate then reacts more slowly, providing the long-term strength.
299. Which of the following is a common use of cement in the construction industry?
ⓐ. As a surface coating for walls
ⓑ. In the manufacture of bricks and tiles
ⓒ. For the production of concrete and mortar
ⓓ. For making insulation materials
Correct Answer: For the production of concrete and mortar
Explanation: Cement is commonly used in the production of concrete and mortar. Concrete is made by mixing cement with sand, gravel, and water, while mortar is used for bonding bricks and stones in construction projects.
300. What is the chemical formula of tricalcium silicate, one of the key compounds in cement?
ⓐ. $Ca_3SiO_5$
ⓑ. $CaSiO_3$
ⓒ. $Ca_2SiO_4$
ⓓ. $Ca_2SiO_3$
Correct Answer: $Ca_3SiO_5$
Explanation: Tricalcium silicate, also known as C₃S, has the chemical formula $Ca_3SiO_5$. It is one of the most important compounds in cement, responsible for the strength development during the hydration process.
Welcome to Class 11 Chemistry MCQs – Chapter 10: The s-Block Elements (Part 3). This section covers advanced topics, including Van der Waals forces and solubility products (Ksp). Perfect for board exams, JEE, and NEET preparation.
Topics covered in Part 3 (100 MCQs)
- Solubility product constant and its role in determining solubility
- Reactions of alkaline earth metals with acids and other reagents
- Industrial applications of s-block elements like the preparation of cement and fertilizers
- 👉 Total MCQs in this chapter: 359 (100 + 100 + 100 + 59)
- 👉 This page: Third set of 100 solved MCQs
- 👉 Next: Continue with Part 4