Question

What is the mass percentage of carbon tetrachloride if $22g$ of benzene is dissolved in $122g$ of carbon tetrachloride?
A: $84.72\% $
B: $15.28\% $
C: $50\% $
D: $44\% $

Answer 1

Hint: Like molarity and molality mass percentage is also one of the ways to represent the concentration of the solution. It is calculated by dividing the mass of the component with the total mass of the mixture, multiplied by $100$.
Formula used: mass percent$ = \dfrac{m}{M} \times 100$
Where $m$ is mass of the substance and $M$ is mass of a mixture

Complete step by step answer:
We know the mass percent of a substance is calculated as the mass of that substance divided by the total mass of the mixture. In this question, we have given the mass of carbon tetrachloride and benzene. We have to calculate the mass percentage of carbon tetrachloride in the mixture of benzene and carbon tetrachloride. We need to write a mass of substance and mass of the mixture.
Mass of substance (carbon tetrachloride) $m = 122g$ (given)
Mass of benzene $ = 22g$ (given)
Mass of mixture$ = $ mass of benzene$ + $mass of carbon tetrachloride
Mass of mixture$\left( M \right) = 22 + 122 = 144g$
Using above formula, mass percent$ = \dfrac{m}{M} \times 100$
We get,
Mass percent$ = \dfrac{{122}}{{144}} \times 100$
Mass percent$ = 84.722\% $
Mass percent of carbon tetrachloride is $84.72\% $.
So, correct answer is option A that is $84.72\% $.

Additional information:
Normality is also a way to define concentration. It is defined as the number of gram equivalents present per $1000mL$ of solution. Equivalent mass is calculated by dividing the molecular mass of substance with valency.


Note:
Molarity and molality both are two different terms. In molality mass of the solvent is used and in molarity volume of solution is used. Molarity is defined as the number of moles present per $1000mL$ of solution and molality is defined as the number of moles present per $Kg$ of solvent.