Hydrogen (H2) gas and oxygen (O2) gas react to form water (H2O) vapor.

Question

Hydrogen (H2) gas and oxygen (O2) gas react to form water (H2O) vapor. 

Suppose you have 5.0 mol of (H2) and 11.0 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.

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Answer 1

Write the balanced equation for the reaction:

2H₂(g) + O₂(g) ==> 2H₂O(g) ... balanced equation

Find limiting reactant:

For H₂: 5.0 mol H₂ x 2 mol H₂O / 2 mol H₂ = 5.0 mol H₂O formed

For O₂: 11.0 mol O₂ x 2 mol H₂O / mol O₂ = 22.0 mol H₂O formed

So, H₂ is the limiting reactant so all of it will react and there will be none left.

If the question is asking how much O₂ is left, we proceed as follows:

moles O₂ that react = 5.0 mol H₂ x 1 mol O₂ / 2 mol H₂ = 2.5 mol O₂ react

moles O₂ left = 11.0 mol - 2.5 mol = 8.5 mol O₂ left