Ethanol burns in air
4 marks · NormalThe table shows the mass of carbon dioxide produced when different masses of ethanol are burned completely in air.
| Mass of ethanol burned (g) | Mass of carbon dioxide produced (g) |
|---|---|
| 2.3 | 4.4 |
| 4.6 | 8.8 |
| 6.9 | 13.2 |
Describe the relationship between the mass of ethanol burned and the mass of carbon dioxide produced.
Calculate the mass of carbon dioxide produced when 11.5 g of ethanol is completely burned.
Suggest a reason why your answer in part b might be slightly lower in a real experiment.
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
(a) The mass of carbon dioxide produced is directly proportional to the mass of ethanol burned.
(b) 22.0 g
(c) Some ethanol may not burn completely or some carbon dioxide may escape measurement.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States or describes the proportional relationship (e.g., directly proportional/double ethanol, double CO2).
M1 (b) · 1 mark · Recognises and applies the ratio from the data or by proportion (e.g., 2.3 g ethanol produces 4.4 g CO2, so 11.5 g produces 5 × 4.4 g = 22.0 g).
A1 (b) · 1 mark · Correct mass of CO2: 22.0 g (allow 21.9–22.1 g for proportional/rounding).
B2 (c) · 1 mark · Gives a sensible source of error (e.g., incomplete combustion, CO2 loss).
Worked solution
a) The mass of carbon dioxide produced is directly proportional to the mass of ethanol burned. For each increase of 2.3 g ethanol, the CO2 increases by 4.4 g.
b) 11.5 g is 5 times 2.3 g (2.3 × 5 = 11.5). Therefore, mass of CO2 = 4.4 g × 5 = 22.0 g.
c) The actual answer may be lower due to incomplete combustion of ethanol or loss of carbon dioxide before measurement.