Question

On heating 4.9 g of $KCl{O}_3$, the weight loss is found to be 0.384 g. The percentage of $KCl{O}_3$ decomposed is:

• A. 20%
• B. 30%
• C. 10%
• D. 40%

Answer 1

The correct option is A 20%

2mol $KCl{O}_3$ will produce 2mol KCl and 3 mol $O_2$

Molar mass $KCl{O}_3$ = $122.55g/mol$

Molar mass $O_2$ = $32g/mol$

0.384g mass loss = 0.384g $O_2$ produced

Mol $O_2$produced = 0.384/32

= 0.012 mol $O_2$

This means that 0.012*2/3 = 0.008 mol $KCl{O}_3$ decomposed

Mass of 0.008 mol $KCl{O}_3$ = 122.55* 0.008

= 0.980g $KCl{O}_3$ decomposed

% $KCl{O}_3$ that decomposed = 0.980/4.9 *100

20% answer A