Calculate the volume of oxygen required for the complete combustion of ethanol with a mass of 2.3 g.

Given:

m (C2H5OH) = 2.3 g.

V (O2) -?

Solution:

Let’s write down the reaction of ethanol combustion:

C2H5OH + 3O2 = 2CO2 + 3H2.

Find the number of moles of alcohol:

n (C2H5OH) = m / Mr = 2.3 g / 46 g / mol = 0.05 mol.

It can be seen from the reaction equation that there is three times more oxygen, which means the number of moles will be:

n (О2) = 3 • n (C2H5OH) = 3 • 0.05 mol = 0.15 mol.

Oxygen volume in the reaction:

V (O2) = n • Vm = 0.15 mol • 22.4 L / mol = 3.36 L.