4.90 g of impure potassium chlorate on heating shows a weight loss of 0.384 g. What percent of the impure potassium chlorate has decomposed?

Options

A. 20
B. 30
C. 40
D. 80

Answer

A

Explanation

Given,
Impure potassium chlorate = 4.90 g
On heating, weight loss = 0.384 g
Equation
`" "2KClO_(3) overset(Delta)(rarr)2KCl+3O_(2)`
2 mol of `KClO_(3)` will produce 2 mol KCl and 3 mol `O_(2)`.
Molar mass of `KClO_(3)=122.55 g//mol`
Molar mass of `O_(2)=32g//mol`
0.384 g loss = 0.384 g `O_(2)` produced
So, produced `O_(2)=0.384/32=0.012 mol`
That means, decomposed
`" "KClO_(3)=122.55 times 0.008=0.980 g`
% of decomposed `KClO_(3)=0.980/4.9 times 100 =20%`