# Question c5bf9

Jan 14, 2014

A mole ratio is used to convert the number of moles of one substance to the number of moles of another substance.

#### Explanation:

A mole ratio or molar ratio a fraction made up from the coefficients in a balanced equation.

For example, in the equation

$\text{6Li(s)" + "N"_2"(g)" → "2Li"_3"N(s)}$

We could have the following mole ratios:

"6 mol Li"/("1 mol N"_2); "6 mol Li"/("2 mol Li"_3"N"); ("1 mol N"_2)/"6 mol Li"; $\left(\text{1 mol N"_2)/("2 mol Li"_3"N}\right)$; ("2 mol Li"_3"N")/"6 mol Li"; and $\left({\text{2 mol Li"_3"N")/("1 mol N}}_{2}\right)$

EXAMPLE 1:

What is the mole ratio between $\text{Li}$ and ${\text{N}}_{2}$ in the reaction?

$\text{6Li(s)" + "N"_2"(g)" → "2Li"_3"N(s)}$

Solution:

"6 mol Li"/("1 mol N"_2) or ("1 mol N"_2)/"6 mol Li"

We pick the fraction that gives us the correct units in a problem.

EXAMPLE 2:

Use the above equation to determine the number of moles of $\text{Li"_3"N}$ that can be prepared using 0.24 mol $\text{Li}$.

Solution

The mole ratio is either "6 mol Li"/("2 mol Li"_3"N") or ("2 mol Li"_3"N")/"6 mol Li".

We choose the one that makes the units cancel and gives the correct units for the answer — the second one.

0.24 color(red)(cancel(color(black)("mol Li"))) × ("2 mol Li"_3"N")/(6 color(red)(cancel(color(black)("mol Li")))) = "0.080 mol Li"_3"N"#