Hydrogen (H2)gas and oxygen gas react to form water (H20) vapor.

Question

Hydrogen (H2) gas and oxygen (O2) gas react to form water (H2O) vapor suppose you have 5.0 mol of (H2) and 9.0 mol of (O2) in a reactor.

Suppose as much as possible of the H2 reacts

How much will be left? Round your answer to the nearest 0.1 mol

Answer 1

The question sugggests that H2 is the limiting reactant (as much as possible reacts) but I would first check it.

The equation is 2 H2 + O2 --> 2 H2O

If all 5.0 moles H2 react, they would form 5.0 mol H2 x 2 mol H2O / 2 mol H2 = 5.0 mol H2O

If all 9.0 moles O2 react, they would form 9.0 mol O2 x 2 mol H2O / 1 mol O2 = 4.5 mol H2O

So, H2 produces LESS product, that means H2 is the limiting reactant, all of it will react. The question is with how much O2?

5.0 mol H2 x 1 mol O2 / 2 mol H2 = 2.5 mol O2

The rest is simple. We had 9.0 mol O2, 2.5 mol reacted with H2, so we have left 9.0 - 2.5 = 7.5 mol O2

As usual, make sure your units cancel, that your sig figs are correct, and don't forget to indicate the 7.5 mo are O2 (excess reactant)!