Question

Consider a mixture of potassium chloride and potassium nitrate that is$\mathbf{43}\mathbf{.2}\mathit{\%}$ potassium by mass. What is the percent $\mathbf{\text{KCl}}$by mass of the original mixture?

Short answer

The percent of $\text{KCl}$by mass of the original mixture isdata-custom-editor="chemistry" $32.8728\%$

Step-by-step solution

Definition of mass percentage

The mass of the element or solute divided by the mass of the compound or solute is defined as mass percentage

Find the molar weight of KCl

The molar weight of$\text{KCl}$ is find by adding the masses of$\text{K\hspace{0.17em}and\hspace{0.17em}Cl}$

$\text{39.0983+35.45=74.5483g/mol}$

As the same, the molar weight of${\text{KNO}}_{\text{3}}$ is$\text{101.1032g/mol}$

Find the mass percentage of  KCl

By divide the molar weight of with molar weight of$\text{KCl}$

$39.0983÷74.5483\approx 52.4469\%$

The mass percent of$\text{Cl\hspace{0.17em}in\hspace{0.17em}KCl\hspace{0.17em}is\hspace{0.17em}47.5531\%}$

Divide the molar weight of $\mathrm{K}$with molar weight of${\text{KNO}}_3$ to find the mass percent of${\text{K\hspace{0.17em}in\hspace{0.17em}KNO}}_{\text{3}}$

$39.0983÷101.1032\approx 38.6717\%$

The mass percent of${\text{NO}}_{\text{3}}$in ${\text{KNO}}_{\text{3}}$is$61.3283\%$

Find the proportion ofKCl in the sample

$32.8728÷100=0.328728$

Converting the value to percentage

$0.328728=32.8728\%$

The percentage of$\text{KCl}$ present in the sample is$32.8728\%$