Ethanol burns in air
3 marks · EasyThe table shows the volume of carbon dioxide produced when different volumes of ethanol are completely burned in air.
| Volume of ethanol burned (cm^3) | Volume of CO2 produced (cm^3) |
|---|---|
| 1 | 2 |
| 2 | 4 |
| 3 | 6 |
| 4 | 8 |
Describe the relationship between the volume of ethanol burned and the volume of carbon dioxide produced.
Predict the volume of carbon dioxide produced if 5 cm^3 of ethanol is completely burned.
Suggest why the volume of carbon dioxide produced is always double the volume of ethanol burned.
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 relationship is directly proportional (the more ethanol burned, the more CO2 formed).
(b) 10 cm^3
(c) Combustion equation shows two moles of CO2 for every mole of ethanol. So the ratio of volumes is 2:1 because of the balanced equation.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States the relationship is directly proportional or proportional.
A1 (b) · 1 mark · Predicts 10 cm^3 CO2 for 5 cm^3 ethanol burned.
B2 (c) · 1 mark · Links 2:1 volume ratio to stoichiometry / balanced equation (each mole of ethanol produces 2 moles of CO2).
Worked solution
a) The relationship is directly proportional.
b) If 5 cm^3 of ethanol is burned, the volume of CO2 = 2 × 5 = 10 cm^3.
c) Two moles of CO2 are made per mole of ethanol burned (from the balanced equation), so the volume of CO2 is always double the volume of ethanol consumed.