MOLE TO MASS AND MASS TO MOLE

Don't let the title fool you! Today's class was really not that hard!

• Some Questions will give you an amount of moles and ask you to determine the mass. Converting moles to mass only requires ONE ADDITIONAL STEP!

Example: When 6.5 mol of Potassium chlorate decomposes, Potassium Chloride and oxygen gas are produced. What mass of potassium chloride is produced?

... What do we do from here? If you're like me, chances are your face looks like the girl above! But do not worry! Let's take it step by step!

a) First write a balanced Chemical equation. You're given potassium chlorate, and its a decomposition reaction to produce potassium Chloride and oxygen gas.

2KClO3 ---> 2KCl + 3O2

b) Next, find the mass of Potassium Chloride produced.

Watch the steps:

Given 6.5 mol of Potassium Chlorate. Trying to find mass of Potassium chloride.

6.5 mol x 2KCL (what you need) = 6.5 mol x 74.6 g(Potassium Chloride)

                  2KClO3(what you have)                    1mol

= 484.9 g

=4.8 x 10^2 g

Getting it? That was an equation from Moles to mass. Let's try one more before we move on

Example: How many grams of silver nitrate are needed to produce 1.02 mol of Silver Chloride?

a) Write a balanced Equation

2 AgNO3 + BaCl2 ---> Ba(NO3)2 + 2AgCl

b) Next find how many grams of silver nitrate are needed to produce 1.02 mol of silver chloride:

1.02 x 2mol AgNO3 (what you need)= 1.02 x 169.9 g

            2mol AgCl                                                 1mol

= 173.30 g

=173 g

Are you starting to get it? GREAT LETS TRY 1 MORE AND SEE HOW YOU DO!

Since we've learned how to convert from moles to mass, lets try from MASS TO MOLES;)

Question: In the reaction between Nitrogen Dioxide and water, Nitric acid and nitrogen monoxide are formed. How many moles of Nitrogen dioxide react if 120.6 g of Nitric Acid are produced?

a) first make a balanced chemical equation:

3 NO2 + H20------> 2HNO3 + NO

b) Now use what you have and solve (given 120.6 g... change that into moles using the steps)

120.6 g x     1 mol     = 1.914 mol x 3NO2(What you need)      

              63 g (HNO3)                         2HNO3 (what you have)

=2.87 mol of NO2

GREAT JOB! 

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