A mole ratio is used to convert the number of moles of one substance to the number of moles of another substance.
A mole ratio or molar ratio a fraction made up from the coefficients in a balanced equation.
For example, in the equation
We could have the following mole ratios:
What is the mole ratio between
We pick the fraction that gives us the correct units in a problem.
Use the above equation to determine the number of moles of
The mole ratio is either
We choose the one that makes the units cancel and gives the correct units for the answer — the second one.