Question

Question #c5bf9

Answer 1

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

`"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"`; `("1 mol N"_2)/("2 mol Li"_3"N")`; `("2 mol Li"_3"N")/"6 mol Li"`; and `("2 mol Li"_3"N")/("1 mol N"_2)`

EXAMPLE 1:

What is the mole ratio between `"Li"` and `"N"_2` in the reaction?

`"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 `"Li"_3"N"` that can be prepared using 0.24 mol `"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"`