A mixture of KCl and KClO₃ weighing 1.65 grams was heated; the dry O₂ generated occupied 143 mL at STP. What percent by mass of the original mixture was KClO₃, which decomposes as follows:
$2 \mathrm { KClO } _ { 3 } ( s ) \rightarrow 2 \mathrm { KCl } ( s ) + 3 \mathrm { O } _ { 2 } ( g )$

Question

A mixture of KCl and KClO₃ weighing 1.65 grams was heated; the dry O₂ generated occupied 143 mL at STP. What percent by mass of the original mixture was KClO₃, which decomposes as follows:

2 \mathrm { KClO } _ { 3 } ( s ) \rightarrow 2 \mathrm { KCl } ( s ) + 3 \mathrm { O } _ { 2 } ( g )

Quizplus · Accepted Answer

The correct answer is A because the decomposition of KClO3 produces O2 gas, and the volume of O2 gas produced can be used to calculate the mass of KClO3 in the original mixture.

A Mixture of KCl and KClO3 Weighing 1 2KClO3(s)→2KCl(s)+3O2(g)2 \mathrm { KClO } _ { 3 } ( s ) \rightarrow 2 \mathrm { KCl } ( s ) + 3 \mathrm { O } _ { 2 } ( g )2KClO3​(s)→2KCl(s)+3O2​(g)

A Mixture of KCl and KClO₃ Weighing 1 $2 \mathrm { KClO } _ { 3 } ( s ) \rightarrow 2 \mathrm { KCl } ( s ) + 3 \mathrm { O } _ { 2 } ( g )$