Question
Sun October 28, 2012 By:
 

1.2g of copper powder on heating gave 1.5g of copper oxide. In another experiment copper oxide contained 25% oxygen. Show that these results are in accordance with the law of constant composition.

Expert Reply
Wed October 31, 2012
1.5 g of copper oxide contains 1.2 g of copper;
 
so, mass of oxygen in this compound = 1.5 - 1.2 = 0.3 g
 
Now, in second sample of copper oxide, mass of oxygen = 25 g
 
so, mass of copper = 100 - 25 = 75 g
 
In first sample;
Mass of copper combining with 0.3 g of oxygen = 1.2 g
so, mass of copper combining with 1 g of oxygen = 1.2/0.3 = 4 g
 
In second sample;
Mass of copper combining with 25 g of oxygen = 75 g
So, mass of copper combining with 1 g of oxygen = 75/25 = 3 g
 
The ratio of mass of copper combining with fixed mass of oxygen is 4:3.
 
Since it is a simple ratio so the law of multiple proportions is verified.
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