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Question
Potassium nitrate on strong heating decomposes as under :
2KNO3 → 2KNO2 + O2
Calculate : Weight of oxygen formed when 5.05g of potassium nitrate decomposes completely.
(K = 39, 0 = 16, N = 14)
Solution
Given equation is: 2KNO3 → 2KNO2 + O2
Molecular mass of KNO3 is : (Atomic mass of K + Atomic mass of N + Atomic mass of O) = (39 + 14 + 16 x 3 ) = 101
Molecular mass of of KNO2 = (39 + 14 + 16 x 2) = 85
Now, decomposition of 101g of KNO3 yield = 16g of O2
So, decomposition of 5.05 g of KNO3 will yield = 16 x 5 .05 / 101 = 0.8 g
Hence, when 5.05g of potassium nitrate decomposes completely 0.8 g of oxygen is formed.
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