401. Which raw material is commonly converted into ethanol during fermentation?
ⓐ. Methoxyethane
ⓑ. Carbon monoxide
ⓒ. Chlorobenzene
ⓓ. Glucose
Correct Answer: Glucose
Explanation: Fermentation is a biochemical route for preparing ethanol. In this process, glucose is converted into ethanol and carbon dioxide in the presence of enzymes from yeast. The reaction occurs under mild conditions compared with many industrial inorganic processes. This route is important because it connects alcohol preparation with biological and industrial chemistry.
402. Which equation represents fermentation of glucose to ethanol?
ⓐ. \[C_6H_{12}O_6 \xrightarrow{\text{yeast}} 2C_3H_7OH + 2CO_2\]
ⓑ. \[C_6H_5Cl + NaOH \rightarrow C_6H_5ONa + NaCl\]
ⓒ. \[C_6H_{12}O_6 \xrightarrow{\text{yeast}} 2C_2H_5OH + 2CO_2\]
ⓓ. \[CH_3CH_2OH \xrightarrow{[O]} CH_3CHO + H_2O\]
Correct Answer: \[C_6H_{12}O_6 \xrightarrow{\text{yeast}} 2C_2H_5OH + 2CO_2\]
Explanation: \(\textbf{Starting material:}\)
Glucose has the formula \(C_6H_{12}O_6\).
\(\textbf{Biochemical agent:}\)
Yeast provides enzymes that convert glucose into ethanol.
\(\textbf{Products:}\)
The products are ethanol, \(C_2H_5OH\), and carbon dioxide, \(CO_2\).
\(\textbf{Balanced equation:}\)
\[
C_6H_{12}O_6 \xrightarrow{\text{yeast}} 2C_2H_5OH + 2CO_2
\]
\(\textbf{Final Answer:}\)
Fermentation of glucose gives ethanol and carbon dioxide.
403. What is the role of yeast in ethanol fermentation?
ⓐ. It acts as a strong reducing metal.
ⓑ. It supplies enzymes for biochemical conversion.
ⓒ. It converts ethanol into methanol.
ⓓ. It supplies metallic sodium for reducing glucose directly.
Correct Answer: It supplies enzymes for biochemical conversion.
Explanation: Yeast contains enzymes that catalyse the conversion of glucose into ethanol and carbon dioxide. The process is biochemical rather than a simple metal reduction. Yeast does not act like \(LiAlH_4\) or sodium metal. Its role is to provide the enzyme system needed for fermentation under suitable conditions.
404. Which gas is evolved along with ethanol during fermentation of glucose?
ⓐ. \(SO_2\)
ⓑ. \(O_2\)
ⓒ. \(CO\)
ⓓ. \(CO_2\)
Correct Answer: \(CO_2\)
Explanation: During fermentation, glucose is broken down to ethanol and carbon dioxide. The balanced equation shows two molecules of \(CO_2\) for each molecule of glucose converted. The gas evolution is one of the recognizable features of fermentation. Hydrogen, oxygen, and carbon monoxide are not the usual gaseous products in this process.
405. How many moles of ethanol are obtained from \(1\) mole of glucose according to the fermentation equation?
ⓐ. \(2\) mol
ⓑ. \(1\) mol
ⓒ. \(3\) mol
ⓓ. \(6\) mol
Correct Answer: \(2\) mol
Explanation: \(\textbf{Given equation:}\)
\[
C_6H_{12}O_6 \xrightarrow{\text{yeast}} 2C_2H_5OH + 2CO_2
\]
\(\textbf{Required:}\)
Moles of ethanol from \(1\) mole of glucose.
\(\textbf{Mole ratio:}\)
From the equation, \(1\) mole of \(C_6H_{12}O_6\) gives \(2\) moles of \(C_2H_5OH\).
\(\textbf{Calculation:}\)
\[
1\,\text{mol glucose} \rightarrow 2\,\text{mol ethanol}
\]
\(\textbf{Final Answer:}\)
\(2\) moles of ethanol are formed.
406. If \(2\) moles of glucose undergo complete fermentation, how many moles of \(CO_2\) are formed?
ⓐ. \(1\) mol
ⓑ. \(2\) mol
ⓒ. \(4\) mol
ⓓ. \(6\) mol
Correct Answer: \(4\) mol
Explanation: \(\textbf{Balanced equation:}\)
\[
C_6H_{12}O_6 \xrightarrow{\text{yeast}} 2C_2H_5OH + 2CO_2
\]
\(\textbf{Mole ratio:}\)
\(1\) mole of glucose produces \(2\) moles of \(CO_2\).
\(\textbf{For 2 moles glucose:}\)
\[
2 \times 2 = 4\,\text{mol}
\]
The result is expressed in moles because the question asks for amount of \(CO_2\).
\(\textbf{Final Answer:}\)
\(4\) moles of \(CO_2\) are formed.
407. Which condition is most suitable for fermentation of glucose to ethanol?
ⓐ. Hot concentrated acid without yeast or enzyme action
ⓑ. Dry ether and Grignard reagent
ⓒ. High-temperature chlorination of benzene
ⓓ. Yeast under suitable mild temperature conditions
Correct Answer: Yeast under suitable mild temperature conditions
Explanation: Fermentation is carried out with yeast because enzymes from yeast catalyse the conversion of glucose to ethanol. Very high temperature would destroy enzyme activity. Strong oxidising agents would not support ethanol formation from glucose in the fermentation sense. Dry ether and Grignard reagents belong to a different alcohol-preparation route.
408. Which statement about fermentation is accurate?
ⓐ. It converts glucose into phenol by chemical substitution.
ⓑ. It converts glucose into ethanol biologically.
ⓒ. It reduces esters using \(LiAlH_4\).
ⓓ. It converts phenol into benzene.
Correct Answer: It converts glucose into ethanol biologically.
Explanation: Fermentation is a biological method for preparing ethanol. Glucose is converted into ethanol and carbon dioxide in the presence of yeast enzymes. Methanol preparation from synthesis gas is a separate industrial process. Reduction with \(LiAlH_4\) and phenol reduction with zinc dust are unrelated transformations.
409. Which pair correctly matches the process with the main alcohol produced?
ⓐ. Fermentation — ethanol
ⓑ. Synthesis gas hydrogenation — ethanol
ⓒ. Dow process — methanol
ⓓ. Williamson synthesis — glycerol
Correct Answer: Fermentation — ethanol
Explanation: Fermentation of glucose produces ethanol as the main alcohol. Synthesis gas hydrogenation is used industrially to prepare methanol, not ethanol. The Dow process is a preparation method for phenol from chlorobenzene. Williamson synthesis is used to prepare ethers rather than glycerol.
410. What is the industrial starting mixture for commercial methanol synthesis?
ⓐ. \(CO_2\) and \(O_2\)
ⓑ. \(CH_4\) and \(Cl_2\)
ⓒ. \(CO\) and \(H_2\)
ⓓ. \(C_6H_{12}O_6\) and yeast
Correct Answer: \(CO\) and \(H_2\)
Explanation: Methanol is commercially prepared from synthesis gas, which contains carbon monoxide and hydrogen. The reaction combines \(CO\) with \(H_2\) in the presence of a suitable catalyst. This route is different from fermentation, which produces ethanol from glucose. The industrial preparation of methanol therefore begins with \(CO\) and \(H_2\).
411. Which equation represents commercial preparation of methanol?
ⓐ. \[C_6H_{12}O_6 \xrightarrow{\text{yeast}} 2C_2H_5OH + 2CO_2\]
ⓑ. \[CO + 2H_2 \xrightarrow{\text{catalyst}} CH_3OH\]
ⓒ. \[CH_3CHO + 2[H] \rightarrow CH_3CH_2OH\]
ⓓ. \[CH_3OH + Na \rightarrow CH_3ONa + \frac{1}{2}H_2\]
Correct Answer: \[CO + 2H_2 \xrightarrow{\text{catalyst}} CH_3OH\]
Explanation: \(\textbf{Starting gases:}\)
Commercial methanol synthesis uses carbon monoxide, \(CO\), and hydrogen, \(H_2\).
\(\textbf{Mole ratio:}\)
One mole of \(CO\) combines with two moles of \(H_2\).
\(\textbf{Product:}\)
The product is methanol, \(CH_3OH\).
\(\textbf{Equation:}\)
\[
CO + 2H_2 \xrightarrow{\text{catalyst}} CH_3OH
\]
\(\textbf{Final Answer:}\)
Methanol is prepared from \(CO\) and \(H_2\) over a catalyst.
412. How many moles of \(H_2\) are required to form \(1\) mole of \(CH_3OH\) from \(CO\)?
ⓐ. \(1\) mol
ⓑ. \(3\) mol
ⓒ. \(4\) mol
ⓓ. \(2\) mol
Correct Answer: \(2\) mol
Explanation: \(\textbf{Balanced equation:}\)
\[
CO + 2H_2 \xrightarrow{\text{catalyst}} CH_3OH
\]
\(\textbf{Required:}\)
Moles of \(H_2\) needed for \(1\) mole of \(CH_3OH\).
\(\textbf{Mole ratio:}\)
The coefficient of \(H_2\) is \(2\), and the coefficient of \(CH_3OH\) is \(1\).
\(\textbf{Result:}\)
\[
1\,\text{mol }CH_3OH \text{ requires }2\,\text{mol }H_2
\]
\(\textbf{Final Answer:}\)
\(2\) moles of \(H_2\) are required.
413. Which alcohol is prepared industrially from \(CO\) and \(H_2\)?
ⓐ. Methanol
ⓑ. Ethanol
ⓒ. Propan-\(2\)-ol
ⓓ. Phenol
Correct Answer: Methanol
Explanation: The reaction of carbon monoxide with hydrogen gives methanol, \(CH_3OH\), under suitable catalytic conditions. This process is an industrial route because it uses synthesis gas as the starting material. Ethanol is commonly prepared by fermentation of glucose or hydration of ethene. Phenol is not an alcohol in the ordinary aliphatic sense and is prepared by different aromatic routes.
414. Which statement correctly compares fermentation and commercial methanol synthesis?
ⓐ. Both use yeast as the main catalyst.
ⓑ. Both produce ethanol from glucose.
ⓒ. Fermentation uses \(CO\) and \(H_2\), while methanol synthesis uses glucose.
ⓓ. Fermentation gives ethanol, while synthesis gas gives methanol.
Correct Answer: Fermentation gives ethanol, while synthesis gas gives methanol.
Explanation: Fermentation converts glucose into ethanol and carbon dioxide using yeast enzymes. Commercial methanol synthesis uses carbon monoxide and hydrogen over a catalyst to produce \(CH_3OH\). The two processes differ in raw materials, conditions, and product alcohol. Confusing them leads to wrong alcohol-preparation mapping.
415. Which statement about synthesis gas in methanol manufacture is correct?
ⓐ. It is a mixture of \(NaOH\) and \(HCl\).
ⓑ. It provides \(CO\) and \(H_2\) for methanol formation.
ⓒ. It is glucose dissolved in water.
ⓓ. It provides \(CO\) and \(HCl\) for methanol formation.
Correct Answer: It provides \(CO\) and \(H_2\) for methanol formation.
Explanation: Synthesis gas is used as the source of carbon monoxide and hydrogen in methanol manufacture. The reaction combines \(CO\) with \(2H_2\) to form \(CH_3OH\). It is not a solution of glucose or a mixture of acid and base. The term is important because it identifies the industrial feedstock for methanol.
416. If \(3\) moles of \(CO\) are completely converted to methanol, how many moles of \(CH_3OH\) are obtained?
ⓐ. \(1\) mol
ⓑ. \(2\) mol
ⓒ. \(3\) mol
ⓓ. \(6\) mol
Correct Answer: \(3\) mol
Explanation: \(\textbf{Balanced equation:}\)
\[
CO + 2H_2 \xrightarrow{\text{catalyst}} CH_3OH
\]
\(\textbf{Mole ratio:}\)
\(1\) mole of \(CO\) gives \(1\) mole of \(CH_3OH\).
\(\textbf{For 3 moles CO:}\)
\[
3\,\text{mol }CO \rightarrow 3\,\text{mol }CH_3OH
\]
\(\textbf{Final Answer:}\)
\(3\) moles of methanol are obtained.
417. Which process produces \(CO_2\) as a co-product?
ⓐ. Fermentation of glucose to ethanol
ⓑ. Catalytic synthesis of methanol from \(CO\)
ⓒ. Reduction of propanone by \(NaBH_4\)
ⓓ. Grignard reaction with formaldehyde
Correct Answer: Fermentation of glucose to ethanol
Explanation: The fermentation equation shows both ethanol and carbon dioxide as products. For each mole of glucose, two moles of \(CO_2\) are formed along with two moles of ethanol. Methanol synthesis from \(CO\) and \(H_2\) gives \(CH_3OH\) as the main product without \(CO_2\) in the basic equation. Reduction and Grignard reactions do not usually produce \(CO_2\) as the characteristic co-product.
418. Which conversion is correctly classified as commercial methanol synthesis?
ⓐ. \(CH_3CHO \rightarrow CH_3CH_2OH\)
ⓑ. \(C_6H_{12}O_6 \rightarrow C_2H_5OH\)
ⓒ. \(CH_2=CH_2 \rightarrow CH_3CH_2OH\)
ⓓ. \(CO + 2H_2 \rightarrow CH_3OH\)
Correct Answer: \(CO + 2H_2 \rightarrow CH_3OH\)
Explanation: Commercial methanol synthesis uses carbon monoxide and hydrogen as reactants. The symbolic conversion is \(CO + 2H_2 \rightarrow CH_3OH\) in the presence of a catalyst. The aldehyde and alkene conversions listed give ethanol. Glucose fermentation also gives ethanol, not methanol.
419. Which product pair is obtained from one mole of glucose in fermentation?
ⓐ. \(CH_3OH\) and \(CO\)
ⓑ. \(CH_3CHO\) and \(H_2\)
ⓒ. \(2C_2H_5OH\) and \(2CO_2\)
ⓓ. \(C_2H_5OC_2H_5\) and \(H_2O\)
Correct Answer: \(2C_2H_5OH\) and \(2CO_2\)
Explanation: \(\textbf{Fermentation equation:}\)
\[
C_6H_{12}O_6 \xrightarrow{\text{yeast}} 2C_2H_5OH + 2CO_2
\]
\(\textbf{Interpretation:}\)
One mole of glucose produces two moles of ethanol and two moles of carbon dioxide.
\(\textbf{Product check:}\)
Methanol, ethanal, and diethyl ether are not the direct products in this fermentation equation.
\(\textbf{Final Answer:}\)
The product pair is \(2C_2H_5OH\) and \(2CO_2\).
420. Which statement best distinguishes ethanol fermentation from alcohol formation by carbonyl reduction?
ⓐ. Fermentation is metal-assisted reduction of aldehydes to alcohols with hydride reagent.
ⓑ. Fermentation is enzyme-assisted conversion of glucose to ethanol.
ⓒ. Fermentation uses Grignard reagents in dry ether.
ⓓ. Fermentation produces phenol from chlorobenzene.
Correct Answer: Fermentation is enzyme-assisted conversion of glucose to ethanol.
Explanation: Fermentation uses enzymes from yeast to convert glucose into ethanol and carbon dioxide. Carbonyl reduction uses reducing agents such as \(NaBH_4\), \(LiAlH_4\), or catalytic hydrogenation to convert aldehydes and ketones into alcohols. Grignard reagents and phenol preparation routes are separate reaction families. The raw material and reaction conditions clearly distinguish fermentation from carbonyl reduction.
