Question

How are mole ratios used in chemical calculations?

Answer 1

In order to determine the mole ratio, we need to begin with a balanced chemical equation.

For this reaction the balanced chemical equation is
`N_2 + 3H_2 -> 2NH_3`

The mole ratios are determined using the coefficients of the substances in the balanced chemical equation.

`1 mol n_2 : 3 mol H_2 : 2 mol NH_3`

The mole ratios for each substance pair would be

`1 mol N_2 : 3 mol H_2`

`(1 mol N_2)/ (3 mol H_2)` or `(3 mol H_2)/ (1 mol N_2)`

`1 mol N_2 : 2 mol NH_3`

`(1 mol N_2)/ (2 mol NH_3)` or `(2 mol NH_3)/ (1 mol N_2)`

`3 mol H_2 : 2 mol NH_3`

`(3 mol H_2)/ (2 mol NH_3)` or `(2 mol NH_3)/ (3 mol H_2)`

Mole ratios are used as a means of comparison of substances in a balanced chemical equation in order to determine amounts.

Using the same reaction for ammonia
`N_2 + 3H_2 -> 2NH_3`

How many moles of Hydrogen gas are necessary to react with 5 moles of Nitrogen.

We can use conversion factors in a process called stoichiometry.

`5 mol N_2 x (3 mol H_2)/(1 mol N_2) = 15 mol H_2`

Mole ratio provides a comparison to cancel units. In this case the moles of Nitrogen cancel and we determine the moles of Hydrogen.

I hope this was helpful.
SMARTERTEACHER