Everything Science Grade 11

CHAPTER 6. QUANTITATIVE ASPECTS OF CHEMICAL CHANGE 6.3

m

n M

Example 3: Calculating moles frommass

QUESTION

Calculate the number of moles of copper thereare in a sample that weighs 127 g.

SOLUTION

Step 1 : Write the equation to calculate the number ofmoles

n =

m

M

Step 2 : Substitute numbers into the equation

n =

127

63. 55

= 2

There are 2 moles of copper in the sample.

Example 4: Calculating mass frommoles