Which compound needs the greatest amount of oxygen for the complete combustion of 1 mol of the compound? A - AQA - A-Level Chemistry - Question 25 - 2021 - Paper 3

Ethanal has the molecular formula C₂H₄O. The combustion reaction is:

$C_2H_4O + 3O_2 \rightarrow 2CO_2 + 2H_2O$

So 3 moles of oxygen are required for 1 mole of ethanal.

Ethane-1,2-diol has the formula C₂H₆O₂. The combustion reaction is:

$C_2H_6O_2 + 3O_2 \rightarrow 2CO_2 + 3H_2O$

This means 3 moles of oxygen are needed for 1 mole of ethane-1,2-diol.

Methanol has the formula CH₃OH. The combustion reaction can be expressed as:

$CH_3OH + 1.5O_2 \rightarrow CO_2 + 2H_2O$

Here, 1.5 moles of oxygen are required for complete combustion of 1 mole of methanol.