Making ethanol by fermentation
2 marks · EasyGlucose can be converted to ethanol and carbon dioxide by fermentation.
Calculate the maximum volume of ethanol that can be produced by fermentation of 10 g of glucose at room temperature, if the yield is 100%. Use the following information:
| Relative molecular mass (M_r) | Molar volume of gas at room temperature |
|---|---|
| Glucose (C_6H_{12}O_6) = 180 | Ethanol (C_2H_5OH) = 46 |
| 1 mol = 24 dm³ (for gases) |
Give your answer in grams. (You may assume the density of ethanol is not needed for this calculation.)
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
5.1 g (±0.1)
Also accept: 5.11 g; 5.10 g
Common mistakes: Dividing by wrong molar mass; Incorrect stoichiometric ratio
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Correctly calculates the moles of glucose or states/glucose to ethanol ratio (from equation: 1 mol glucose produces 2 mol ethanol) (follow-through)
A1 · 1 mark · Correct final answer for grams of ethanol produced from 10 g glucose (5.1 g), to 1 decimal place. (follow-through)
Worked solution
The fermentation equation is:
Calculate moles of glucose:
From the equation, 1 mol glucose produces 2 mol ethanol. Calculate moles of ethanol:
Calculate mass of ethanol:
Answer: 5.1 g