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)

Answer 1

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.