Question

A solution is prepared by adding 2 g of substance A to 18 g of water. The mass percent of the solute is
A. 10
B. 20
C. 40
D. 25

Answer 1

Hint: A solution consisting of two components is called a binary solution. The components of a binary solution are called the solute and the solvent. A substance (small amount) that dissolves in a large amount of the solvent to form a solution is called the solute. During the solution formation, the components which are present in large excess are called the solvent. They have the same physicality as the solution. For example in the aqueous solution of $NaCl$ and, $AgN{O_3}$etc. water is the solvent.

Complete step by step answer:
The concentration of the solution in terms of percentage can be expressed in this way
Mass to mass percentage $ = \dfrac{{mass\,of\,solute\,in\,gms}}{{mass\,of\,solution\,in\,gms}} \times 100\% $
In the question, we have to find the mass percentage of the solute. Applying the above formula we can calculate the mass percentage of the solute.
Given,

Mass of solute $ = 2$gms
Mass of solution $ = $(mass of the solute $ + $mass of solvent)
$ = \left( {2 + 18} \right)gms$
$ = 20$gms
(Since a solution contains solute and solvent and the mass of the solute and solvent is also given so we have calculated the mass of the solution).
Now, applying the above formula to calculate the mass percent of the solute.
The mass percent of the solute $ = \dfrac{{mass\,of\,solute\,in\,gms}}{{mass\,of\,solution\,in\,gms}} \times 100\% $
$ = \dfrac{{2g}}{{20g}} \times 100\% $
$ = \dfrac{1}{{10}} \times 100\% $
$ = 10\% $

(we have put the given values in the formula and after calculating we have the value of mass percent of the solute which is $10\% $)

Therefore, the mass percent of the solute is $10\% $.

So, the correct answer is Option A .

Note: Depending upon the nature of the solvent, we have the following three main types of solution:

Gaseous solution: - All gases and vapor form homogeneous mixtures. Therefore the mixture of gases is regarded as solutions. These solutions get formed spontaneously and quickly.

Liquid solution: - These solutions can be obtained by mixing solids or gases in liquids or two substances which are themselves liquids. Liquid solutions can also be obtained by mixing two solids.

Solid solutions: - Many solids can form a solution of this type. For example, copper and gold can form a solid solution because gold atoms can replace copper atoms in the crystal lattice of copper.