Question

Choose the correct set if ' $\mathrm{T}$ ' is true statement and ' $\mathrm{F}$ ' is false statement : (A) In the preparation of ethanol, if its percentage exceeds $14\mathrm{\%}$, then action of zymase is prohibited. (B) Methanol and ethanol both are colourless liquid but boils at $337\mathrm{K}$ and $351\mathrm{K}$ respectively. (C) If air gets into fermentation, taste of alcoholic drinks destroy because of formation of ethanoic acid. (D) Methanol is produced by reaction $:\mathrm{CO}+2{\mathrm{H}}_2\frac{\mathrm{ZnO}-{\mathrm{Cr}}_2{\mathrm{O}}_3}{200-300\mathrm{atm}}⟶{\mathrm{CH}}_3\mathrm{OH}$ (A) T T F F (B) T TFT (C) $\mathrm{T}\mathrm{T}\mathrm{TF}$ (D) TTTT

Short answer

(D) TTTT

Step-by-step solution

Statement A

In the fermentation process, zymase is an enzyme complex responsible for converting sugar (glucose) into ethanol. When the ethanol concentration exceeds 14%, the efficiency of zymase decreases as its activity is inhibited. Therefore, statement A is true (T).

Statement B

Methanol (CH3OH) and ethanol (C2H5OH) are both colorless liquids. However, their boiling points are different. Methanol has a boiling point of 337 K, and ethanol has a boiling point of 351 K. So, statement B correctly states the boiling points of methanol and ethanol. Hence, statement B is true (T).

Statement C

Ethanol fermentation is an anaerobic process, which means it takes place in the absence of oxygen. If air (oxygen) infiltrates the process, aerobic bacteria such as Acetobacter can oxidize the ethanol to produce ethanoic (acetic) acid. Acetic acid imparts an undesirable sour taste to alcoholic beverages. Thus, statement C accurately explains the effect of air on the taste of alcoholic drinks. Therefore, statement C is true (T).

Statement D

Methanol can be produced via certain chemical reactions, including the synthesis reaction involving carbon monoxide (CO) and hydrogen gas (H2) in the presence of a catalyst. The reaction mentioned in statement D is: $$CO+2H_2\underset{ZnO/C{r}_2{O}_3}{\overset{200-300atm}{\to }}C{H}_{3}OH$$ So, statement D accurately describes the production of methanol involving a reaction between CO and H2 in the presence of a ZnO-Cr2O3 catalyst system at high pressure. Therefore, statement D is true (T). Since all statements A, B, C, and D are true, the correct set is:

Answer

(D) TTTT

Key concepts

Ethanol Fermentation

Ethanol fermentation is a biological process that converts sugars, such as glucose, into ethanol and carbon dioxide. This reaction involves enzymes, specifically the enzyme complex zymase, which facilitates this conversion while releasing energy. Fermentation is crucial in various industries like brewing and biofuel production.

The process typically occurs in anaerobic conditions, meaning it happens without the presence of oxygen. This lack of oxygen is vital because it allows for the economic conversion of sugars into ethanol without unwanted by-products such as acetic acid. However, if the ethanol concentration exceeds 14%, zymase's activity diminishes, slowing down the fermentation process. Zymase's efficiency is compromised when alcohol concentration exceeds this threshold, making it essential to monitor the ethanol content during fermentation.

• Zymase is essential in converting sugars to ethanol.
• Operates optimally under anaerobic conditions.
• Efficiency decreases if ethanol concentration is too high.

Boiling Point

The boiling point of a substance is the temperature at which it changes from a liquid to a gas. It is an essential property in characterizing liquids, including different alcohols such as methanol and ethanol. Methanol has a boiling point of 337 K, while ethanol's is slightly higher at 351 K.

The difference in boiling points is due to their molecular structures and intermolecular forces. Methanol is a smaller molecule compared to ethanol, which gives it a lower boiling point. Both molecules can form hydrogen bonds due to the presence of an -OH group, but ethanol’s larger size and additional carbon atom contribute to stronger van der Waals forces, raising its boiling point.

Understanding boiling points is crucial for processes like distillation, where separation of components is based on their boiling points. In industrial and laboratory settings, knowing the exact boiling points helps in purifying chemicals and preparing distilled beverages.

• Boiling point indicates the temperature for phase change.
• Different for methanol (337 K) and ethanol (351 K).
• Depends on molecular structure and intermolecular forces.

Chemical Reactions

Chemical reactions are processes where substances, known as reactants, transform into different substances called products. These transformations involve breaking and forming chemical bonds. In organic chemistry, numerous reactions explore these changes, including those involved in producing and using alcohols like methanol and ethanol.

For instance, methanol production is a classic example of a chemical reaction where carbon monoxide (CO) reacts with hydrogen (H2) to form methanol ( CH3OH ). This reaction occurs under specific conditions involving high pressure and catalysts like ZnO and Cr2O3. Catalysts are substances that accelerate reactions without being consumed, ensuring more efficient production processes.

• Chemical reactions involve breaking and making chemical bonds.
• Production of methanol involves a reaction of CO and H2.
• Catalysts like ZnO/Cr2O3 speed up reactions without being used up.

Anaerobic Process

An anaerobic process occurs in the absence of oxygen. It is fundamental in various biological systems and industrial applications, such as the production of ethanol by fermentation. In these settings, microorganisms metabolize sugars anaerobically, leading to ethanol and carbon dioxide production.

Because oxygen is not involved, anaerobic processes rely on different pathways than aerobic ones. These processes generally yield less energy than aerobic ones but are essential when oxygen is limited or undesirable. The absence of oxygen also prevents the conversion of ethanol into unwanted by-products like acetic acid, maintaining desired product qualities in fermented goods.

In the context of ethanol fermentation, maintaining anaerobic conditions prevents aerobic bacteria from thriving, which might otherwise oxidize ethanol to acetic acid, altering the taste of alcoholic beverages. Therefore, ensuring a proper anaerobic environment is critical in producing high-quality alcoholic products.

• Anaerobic processes do not require oxygen.
• Key for ethanol fermentation and maintaining product integrity.
• Prevents oxidation of ethanol into acetic acid.