A mixture of KClO3 and KCl with a mass of 0.950 g was heated to produce O2. After heating, the mass of residue was 0.740 g. Assuming all the KClO3 decomposed to KCl and O2, calculate the mass percent

Question

of KClO₃ in the original mixture

Answer 1

The balanced equation: 2KClO3 ----> 2KCl + 3O2

Let X be the initial mass of KClO3, then 0.950 -X = the mass of KCl in the mixture.

As the total solid mass after the reaction is 0.740g, this mass minus the initial mass of KCl is given by

0.740g - (0.950 - X) which is = to the mass of KCl produced by the reaction.

The balanced equation shows that for every gram of KCl produced, 1.644g KClO3 is needed (formula mass KClO3/formula mass KCl), so the mass of KClO3 initially is given by 1.644 x[ 0.740 - (0950 - X) ] which is equal to X (initial mass of KClO3).

Solve the following equation for X: 1.644 x [ 0.740 - (0.950 - X) ] = X

X = 0.530 g KClO3

Mass % = 0.530g /0.950 x 100 = 55.8%

Check my math.