Question

A solution contains 50mL of ethyl alcohol mixed with 150 mL of water. Calculate the concentration of the solution.

Answer 1

Hint: A solution refers to a homogeneous mixture consisting of a solute being dissolved completely into a solvent. Here, the solute is a substance which is being completely dissolved, whereas, the solvent is a dissolving medium.

Complete step by step answer:
Here, liquid solute is ethyl alcohol while dissolving medium or liquid solvent is water. Thus, solution is a homogeneous mixture of ethyl alcohol being dissolved in water. Now, we have to determine the concentration of this solution. Concentration of solution can be calculated with the following formula:
$Concentration{\text{ }}of{\text{ }}solution = \dfrac{{Volume{\text{ }}of{\text{ }}solute}}{{Volume{\text{ }}of{\text{ }}solution}} \times 100$
We are given with the following information in the question:
Volume of solute (i.e. ethyl alcohol) $ = 50mL$
Volume of solvent (i.e. water) $ = 150mL$
Thus, Volume of solution = Volume of solute + Volume of solvent
$ = 50 + 150 = 200mL$
Now, we will be substituting these values i.e. Volume of solute as well as Volume of solution in the Concentration formula to attain the desired result in percentage form.
$Concentration{\text{ }}of{\text{ }}solution = \dfrac{{50}}{{200}} \times 100 = 25\% $

Hence, the concentration of the solution is 25% (by volume).

Note:
There are several methods to express concentration of a solution. For instance, it can be expressed in terms of molarity (i.e. moles of solute per litre of a solution), or mole fraction (i.e. the ratio of a number of moles of solute to a total number of moles of the substances present), or mass percentage (i.e. a ratio of the mass of the solute particle to the mass of the solution multiplied by 100) or parts per thousand (ppt).