Question

Ethanol burns according to the following equation. If 15.0 mol of C2H5OH burns this way, how many moles of oxygen are needed?

This image shows C sub 2 H sub 5 OH + 3O sub 2, reaction arrow, 2CO sub 2 + 3H sub 2 O.

Answer 1

Reaction for this process is next:

$$\mathrm{C_2H_5OH} + 3\mathrm{O_2} = 2\mathrm{CO_2} + 3\mathrm{H_2O}$$

As can you see the molar ratio is 1:3 ($\mathrm{C_2H_5OH : O_2}$)

So if you have 15 mol of ethanol, you need $15*3 = 45.0$ mol of $\mathrm{O_2}$ to completely burn all your alcohol.