calculate the percent composition by mass of each element in kclo₃.

Explanation:

Step1: Find molar masses

The molar mass of $K$ is $M_{K}=39.10\ g/mol$, $Cl$ is $M_{Cl}=35.45\ g/mol$, and $O$ is $M_{O}=16.00\ g/mol$. The molar mass of $KClO_{3}$ is $M = 39.10+35.45 + 3\times16.00=39.10 + 35.45+48.00 = 122.55\ g/mol$.

Step2: Calculate percent - mass of K

The percent - mass of $K$ is $\text{Percent - mass of }K=\frac{39.10}{122.55}\times100%\approx 31.90%$.

Step3: Calculate percent - mass of Cl

The percent - mass of $Cl$ is $\text{Percent - mass of }Cl=\frac{35.45}{122.55}\times100%\approx 28.93%$.

Step4: Calculate percent - mass of O

The percent - mass of $O$ is $\text{Percent - mass of }O=\frac{48.00}{122.55}\times100%\approx 39.17%$.

Answer:

Percent - mass of $K\approx31.90%$, Percent - mass of $Cl\approx28.93%$, Percent - mass of $O\approx39.17%$