# For complete combustion of 1 mole of which substance requires the greatest amount of oxygen?

**For complete combustion of 1 mole of which substance requires the greatest amount of oxygen? 1) C 2) P 3) H2 4) Li 5) Si**

In order to determine where the greatest amount of oxygen is required for combustion, it is necessary to draw up chemical equations:

1.C + O2 = CO2

2.Si + O2 = SiO2

3.4P + 5O2 = 2P2O5 (correct answer)

4.2H2 + O2 = 2H2O

5.4Li + O2 = 2Li2O

We look at the coefficients in front of oxygen and other substances and compare them. In the first and second equations, before oxygen, silicon, carbon, the coefficients = “1”, it follows that for the combustion of one mole of C (Si), 1 mole of oxygen is needed. From the third equation, it can be seen that for the combustion of 4 mol of P, 5 mol of O2 is required, then for the combustion of 1 mol of P, 5/4 mol of O2 (1.25 mol) is required. Consider the other reactions in the same way.