Question

Calculate the mass of oxygen obtained by complete decomposition of 10 kg of pure potassium chlorate (Atomic mass K = 39, 0 = 16 and Cl 35.5):

• A. 39.2 kg
• B. 392 kg
• C. 3.92 kg
• D. 3 kg

Answer 1

The correct option is C 3.92 kg

$2KCl{O}_3\to 2KCl+3O_2$

2 moles of KClO${}_3$ form 3 moles of $O_2$

or 2 x 122.5g of KClO${}_3$ form 3 x 32g of $O_2$

10 x 10${}^3$g of KClO${}_3$ form $\frac{3\times 32}{2\times 122.5}\times 10\times {10}^3$ g $=3.92kg$