Question

Sum of mole fraction of all components of a solution is unity
A) True
B) False

Answer 1

Mole fraction is calculated from the number moles of all components and the number of moles is calculated by using the ratio of the weight of a substance and Gram molecular weight of the substance.

Complete answer:
The solution is a homogeneous mixture containing two components such as solvent and solute.
To find the fraction of solute and solvent the mole fraction is used.
Mole fraction defined as the number of moles of a constituent is divided by the total number of moles of constituents in solution.
Mole fraction of all components is unity it is proved by taking one example
Assume a solution containing one solute and one solvent
Formula for finding Mole fraction of solute = ${X_{Solute}} = \frac{{{n_{solute}}}}{{{n_{solute}} + {n_{solvent}}}}$
Assume number of moles of solute is 2.5
Number of moles of solvent is 55.5 moles
Now mole fraction of solute = $\frac{{2.5}}{{2.5 + 55.5}} = 0.043$
Mole fraction of solute + Mole fraction of Solvent =1
0.043+Mole fraction of solvent =1
Mole fraction solvent =1-0.043= 0.957
So calculate mole fraction of solvent to prove mole fraction of all components is unity
$Mole\;fraction\;of\;solvent = \frac{{number\;of\;moles\;of\;solvent}}{{number\;of\;moles\;of\;solute\; + number\;of\;moles\;of\;solvent}}$
Mole fraction of solvent = $\frac{{55.5}}{{55.5 + 2.5}} = 0.957$
So from the above example concluded mole fraction of all components is unity
So answer is (A) True

Note:
The solution is containing solute and solvent and for calculating a mole fraction of solution the number of moles of all components should be considered.