Question

Question #a106e

Answer 1

Mole ratios are used as conversion factors between products and reactants in stoichiometry calculations.

For example, in the reaction

2H₂(g) + O₂(g) → 2H₂O(g)

The mole ratio between O₂ and H₂O is `(1 mol O₂)/(2 mol H₂O)`.

The mole ratio between H₂ and H₂O is `(2 mol H₂)/(2 mol H₂O)`.

Example:

How many moles of O₂ are required to form 5.00 moles of H₂O?

Solution:

5.00 mol H₂O × `(1 mol O₂)/(2 mol H₂O)` = 2.50 mol O₂.

If the question had been stated in terms of grams, you would have had to convert grams of H₂O to moles of H₂O, then moles of H₂O to moles of O₂ (as above), and finally moles of O₂ to grams of O₂.