Industrial Uses of Methanol and Ethanol - UNSOLVED PRACTICE SET

Q7. How is methanol prepared industrially from synthesis gas? Write the reaction and mention the catalyst.

Q8. What is power alcohol? Why is ethanol mixed with petrol for use as fuel?

Q9. Why is methanol called "wood alcohol"? How is it different from ethanol in terms of preparation and toxicity?

Q10. What is denatured alcohol? Why is ethanol denatured before industrial use?

Q11. Write the reaction for the fermentation of glucose to ethanol. What enzyme catalyzes this reaction?

Q12. Your father uses ethanol-based hand sanitizer. Why is ethanol effective in killing germs? What concentration is most effective?

Q13. (a) Describe the industrial preparation of methanol from synthesis gas (water gas).

(b) Write the reactions involved and mention the conditions (temperature, pressure, catalyst).

(c) What are the major uses of methanol in industry?

(d) Why is methanol considered a potential future fuel?

Q14. (a) Describe the industrial preparation of ethanol by:

(i) Hydration of ethene

(ii) Fermentation of molasses

(b) Compare the two methods in terms of:

(i) Raw materials

(ii) Energy requirements

(iii) Purity of product

(iv) Environmental impact

(c) Why is fermentation preferred in India for ethanol production?

Q15. (a) What is power alcohol? Describe its advantages and disadvantages as a fuel.

(b) Explain why ethanol is mixed with petrol (gasohol). What percentage is typically used in India?

(c) What are the environmental benefits of using ethanol-blended petrol?

(d) Why is methanol not used as extensively as ethanol in fuel blending?

Q16. The industrial production of methanol involves the following reaction:

CO + 2H₂ → CH₃OH

ΔH = -90.7 kJ/mol

(a) If 280 kg of CO is used, calculate the theoretical yield of methanol. (Atomic masses: C = 12, O = 16, H = 1)

(b) The reaction is carried out at 250°C and 50-100 atm pressure using ZnO/Cr₂O₃ catalyst. Why are high pressure and low temperature favoured thermodynamically?

(c) In practice, the temperature is maintained at 250°C rather than room temperature. Why? (Consider kinetic factors.)

(d) If the actual yield is 320 kg of methanol from 280 kg of CO, calculate the percentage yield.

(e) A company produces 1000 tonnes of methanol per day. Calculate the daily requirement of CO and H₂ in tonnes.

Q17. The following data relates to ethanol production and use in India:

(a) Calculate the ethanol requirement to achieve E20 blending.

(b) Calculate the total ethanol that can be produced from available molasses.

(c) Is the molasses-based production sufficient to meet E20 target? If not, calculate the deficit.

(d) Suggest alternative feedstocks for ethanol production to meet the deficit. (Consider lignocellulosic biomass, rice straw, etc.)

(e) Calculate the reduction in CO₂ emissions if E20 is implemented, assuming petrol combustion releases 2.3 kg CO₂ per litre and ethanol combustion releases 1.5 kg CO₂ per litre. (Density of petrol ≈ 0.75 kg/L, ethanol ≈ 0.789 kg/L)

Q18. In a school science exhibition, students create a display on "Alcohols in Everyday Life."

(a) A student displays a bottle of hand sanitizer containing 70% ethanol. Why is 70% ethanol more effective than 95% ethanol for sanitization? (Consider protein denaturation and water content.)

(b) Another student shows that methanol is used as a windshield washer fluid in cold countries. Why is methanol preferred over ethanol for this purpose? (Consider freezing point and cost.)

(c) A third student presents data on methanol poisoning incidents in India, often caused by consuming illicit liquor adulterated with methanol. Explain why methanol is so toxic. (Consider metabolic pathway: methanol → formaldehyde → formic acid.)

(d) The students learn that Brazil runs most of its cars on ethanol (flex-fuel vehicles). Brazil produces ethanol from sugarcane, while the US produces it from corn. Compare the two approaches in terms of:

Energy balance (energy output vs. input)

Land use

Food vs. fuel debate

Carbon footprint

(e) The teacher asks: "India has set a target of net-zero emissions by 2070. How can ethanol and methanol contribute to this goal? What challenges need to be overcome?" Frame a comprehensive answer.