UNIT # 7 Introduction Objectives Problems 1 | 2 | 3 | 4 | 5

CALCULATIONS BASED ON FORMULAE

7.5 - Calculations involving Avogadro's number

7.5.3 - Mass in grams to number of particles conversion

Whenever you want to convert quantities from one unit to another, you need to use the appropriate conversion factor. The conversion factor must have units of the two quantities involved.

To convert between mass in grams and number of particles* it will require two steps as there is not a single quantity that relates these two units.

 Step 1: Convert the mass in grams to moles. This step is explained in detail in section 7.5.1. Step 2: Convert the calculated quantity from step 1 in moles to the number of particles. This step is explained in detail in section 7.5.2.

*

For example:

How many oxygen atoms are there in 5.0 grams of Na2CO3?

These are the steps that I would take to answer the question.

Step 1: How many moles of Na2CO3 are there in 5.0 grams of Na2CO3?

Step 2: In this many moles of Na2CO3, as calculated in step 1, how many moles of oxygen atoms are there?
Step 3: In this many moles of oxygen, as calculated in step 2, how many oxygen atoms are there?

Section 8.2
Calculation of Moles of Units. Avogadro's Number (N) ..p189

 Back Next
 All contents copyrighted © 1996-2006 British Columbia Institute of Technology Chemistry Department - 3700 Willingdon Avenue Burnaby, B.C. Canada V5G 3H2