245 gram of $KCl{O}_3$on decomposition produce 2.4 gram of $O_2$.What is % purity of $KCl{O}_3$?

Gram molecular weight of $KCl{O}_3=39+35.5+48=122.5gram/mole$

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

According to equation 245 gram of $KCl{O}_3$should produce $3\times 32=96gramof{O}_2$ if $KCl{O}_3$is 100 % pure.

96 gm of $O_2$is produced when $KCl{O}_3$is 100 percent pure.

When 2.4 gm of $O_2$is produced , the percentage purity is $\frac{100}{96}\times 2.4 = 2.5$