Mass to Mass

Today we learned about Mass to Mass problems!

Example:

How many grams of O2 are produced from the decomposition of 3.0 g of Potassium Chlorate?


This question gives us grams, but we must change it to grams of another element. First we must write a balanced Chemical equation:

2KClO3 ----> 2K + Cl2 + 3O2


Than we take what we are given, which is 3.0 grams. Change 3.0 grams into moles, than find what you need over what you have, than with the moles you are given, find grams!


3.0 g x 1 mol/122.6 g = 0.024 mol x 3 O2 mol/ 2 KClO3 = 0.036 mol x 32.0 g/1mol
= 1.2 g

Let's try one more!

Example:

Determine the mass of lithium hydroxide produced when 0.38 g of lithium nitride reacts with water according to the following equation:

Li3N +3H2O ---> NH3+ 3LiOH


0.38 g x 1 mol/34.7 g = 0.011 mol x 23.95 g LiOH/1mol = 0.033 g x 23.9 g/ 1 mol
= 0.78 mol


Try some mass to mass problems, too!