Question

The mole fraction of solute in a solution is $0.3$. The mole percent of solvent is:
A. $30$
B. $70$
C. $60$
D. $40$

Answer 1

Hint: We know that, the mole fraction is defined by the fraction of the number of molecules to the total number of moles that are present in any chemical compound.

Complete step by step answer:
As we all know, the mole fraction of solute and solvent are different. If the value of one of the mole fraction is given, then the value of another can be calculated by simply subtracting the given mole fraction from one. The mole percent of any solution can be determined by using the value of a mole fraction of solvent, which multiplies with the hundred percent.
Given, the value of mole fraction of solute in a solution is $0.3$.
The mole fraction of solvent can be calculated by using the formula given below.
${\rm{Mole}}\;{\rm{fraction}}\;{\rm{of}}\;{\rm{solvent}} = 1 - {\rm{Mole}}\;{\rm{fraction}}\;{\rm{of}}\;{\rm{solute}}$
Substitute the respective values in the above equation.
$\begin{array}{c}
{\rm{Mole}}\;{\rm{fraction}}\;{\rm{of}}\;{\rm{solvent}} = 1 - {\rm{0}}{\rm{.3}}\\
 = 0.7
\end{array}$
The value of mole fraction of solvent is $0.7$.
The mole percent of solvent in a solution can be calculated by using the formula given below.
${\rm{Mole}}\;{\rm{percent}}\;{\rm{of}}\;{\rm{solvent}} = {{\rm{\chi }}_{\rm{a}}} \times {\rm{100\% }}$
Where, ${{\rm{\chi }}_{\rm{a}}}$ is the mole fraction of solvent in the given solution.
Substitute all the respective values in the above equation.
$\begin{array}{c}
{\rm{Mole}}\;{\rm{percent}}\;{\rm{of}}\;{\rm{solvent}} = {\rm{0}}{\rm{.7}} \times {\rm{100\% }}\\
 = {\rm{70\% }}
\end{array}$
Thus, the mole percent of solvent in a solution is $70\% $.
Therefore, the correct option for this given question is B that is $70$.
Note:
The solution is one of the renowned homogenous mixtures and it consists of both the quantities they are solute and solvent. Mole fraction is one of the ways to express the concentration of solution. Its value is unitless.