Question

A high temperature reaction vessel is charged with 0.5860 mol of iron powder and 35.1 L of oxygen gas at standard temperature pressure. On heating, the iron and oxygen react according to the balanced reaction below.
4Fe(s) + 3O2(g) ®️ 2Fe2O3(s)

After the reaction vessel is called, and assuming the reaction goes to completion, what volume of oxygen remains?

Answer 1

Answer: 25.1195 L

Explanation:

Given:

There are 0.5860 mol of Iron powder (Fe)

The volume of oxygen gas at STP is 31.5 L

The volume filled by a gas at STP is approximately 22.71 L

Therefore, the moles of oxygen gas at STP = Volume of oxygen gas at STP/ 22.71

= 35.1/22.71

= 1.5456 mol

The balanced chemical equation given for this reaction is:

4Fe(s) + 3O2 (g) ----> 2Fe2O3 (s)

Dividing the above equation by 2, yields:

2Fe(s) + 3/2O2(g) -------> Fe2O3 (s)

From the equation we see:

2 moles of Fe reacts with 3/2 mole of O2 to give one mole of Fe2O3

Thus, let x moles of O2 react with 0.5860 moles of Fe

0.5860/2=x/3/2

0.5860*3=4*x

x = 1.758/4

x =0.4395 mol

So the remaining moles of oxygen gas = 1.5456 - 0.4395

= 1.1061 mol

Therefore, the amount of oxygen gas, in litres, remaining is = 1.1061*22.71

= 25.1195 L