Question

What is the meaning of $10\%$ solution of ${\rm{NaCl}}$?
(A) $10$g ${\rm{NaCl}}$ in $100$ grams of solution
(B) $58.5$ grams of ${\rm{NaCl}}$ in$100$ grams of solution
(C) $94$ grams ${\rm{NaCl}}$ in $100$ grams of solution
(D) $5.85$ grams of ${{\rm{H}}_{\rm{2}}}{\rm{O}}$ in$100$ grams of solution

Answer 1

We know that solution is made up by dissolving solute in the solvent here in the question the scientific terms is used to describe the amount of solute dissolve in solvent. In the question solute means ${\rm{NaCl}}$ and the solvent is water. The molecular weight of ${\rm{NaCl}}$is $54.8\,g/mol$ which is different from the weight we weigh in a weighing pan. The molecular weight is $\,g/mol$ and the weight we weigh is in grams.

Complete step by step solution: $10\%$ solution of ${\rm{NaCl}}$ means that the amount of sodium chloride in terms of weight we have measured in weighing pan is dissolved in${\rm{100 ml}}$ water to make solution.
The different ways by which the percentage of solution can be measure $w/w{\rm{ }},m/m{\rm{ }},m/v{\rm{ }},w/v$ it can be read as the percentage weight of solute dissolved in weight of solvent, mass of solute in mass of solvent, mass of solute in volume of solvent, and so on. Here, in the question it is the mass of sodium chloride as solute in the given solvent.
There are different ways by which we can determine the concentration of solute in the solvent to make the solution. They are normality, molarity, molality, ppm, etc. These have different units and are used to calculate the concentration of the solution.
Now, $10\%$solution of ${\rm{NaCl}}$ means $10$g ${\rm{NaCl}}$ in $100$ grams of solution. Let’s show this as follows;

$${\rm{Percent}}\;{\rm{by}}\;{\rm{mass}} = \frac{{{\rm{10}}\;{\rm{g}}\;{\rm{NaCl}}}}{{{\rm{100}}\;{\rm{g}}\;{\rm{Solution}}}} \times 100\\\ \Rightarrow {\rm{Percent}}\;{\rm{by}}\;{\rm{mass}} = 10$$

Hence, the correct option is (A).

Note: It should be noted that a lot of terms are there to represent concentration of solution but we decide on the basis of the unit or the way of representation. ppm is the most important unit used to measure concentration of the solute in parts per million levels. It is used to measure chemicals present in the water which is used for drinking purposes.