Question

What do you mean by concentration of solution? A solution contains $40g$ of sugar in $200g$ of water. Calculate the concentration in terms of Mass by mass percentage of solution.

Answer 1

Concentration is the measurement of the amount of solute present that has been dissolved in a solvent or the solution. There are several ways of expressing concentration of solution i.e. Molarity, Molality, Mass percentage, Volume percentage, Normality, parts per million (ppm) etc.

Complete answer:
Let us consider all the formulas-
Molarity- It is defined as Number of moles of solute present in 1 litre of solution.
$Molarity = \dfrac{n}{V}$ where $n$ is the number of moles of solute and $V$ is the volume of solution in litres.
Molality- It is defined as the number of moles of solute present in $1kg$of solvent.
$Molality = \dfrac{n}{W}$where $n$ is the number of moles of solute and $W$ is weight of solvent in kilograms.
Mass percentage- It is calculated as mass of solute present in mass of solution expressed as percent.
Mass percentage= (Mass of solute/Mass of solution)*100%
Volume percentage- It is calculated as volume of solute present in volume of solution expressed as percent.
Volume percentage= (Volume of solute/Volume of solution)*100%
Normality- It is defined as number of gram equivalent present in a litre of solution,
$Normality = \dfrac{{Eq}}{V}$ where $Eq$ is number of gram Equivalents given as-
Given mass of solute/Equivalent mass where Equivalent mass=Molar mass/n-factor
Here n- factor is basicity, Acidity or total positive or negative charge in Acid, Base and Salt respectively.
In the question we are given,
Mass of sugar (Solute)$= 40gm$
Mass of water (Solvent)$= 200gm$
Mass of solution (Solute+Solvent) will be $= 40 + 200 = 240gm$
So Mass percentage will be$= \dfrac{{40}}{{240}} \times 100 = 16.67\%$

Note:
The idea of determining concentration of solution is very important in Chemistry laboratories as well as in everyday life. This is useful to study chemical reactions and hence study the reaction rates. It can also determine the condition of equilibrium of the chemical reaction. By knowing the concentration we can determine whether the solution is dilute or concentrated.