Question

A quantity of 50g of water is saturated with HCl gas to get 75 ml of solution containing 40% HCl, by mass. The density of the solution forms is--------.
A. 1.11 g/ml
B. 0.4 g/ml
C. 0.9 g/ml
D. 0.99 g/ml

Answer 1

Hint: Density of the solution is nothing but the number of grams of the solute present in the total volume of the solution. There is a formula to calculate the density of the solution and it is as follows.
\[\text{Density=}\dfrac{\text{mass of the solution}}{\text{total volume of the solution}}\]

Complete step by step answer:
- In the question it is given that a quantity of 50 g of water is saturated with HCl to get 75 ml of 40% HCl by mass.
- 40% means 40 g of HCl in 100 g of solution.
-Then the mass of water = 100 g - 40 g = 60 g
-Therefore 40 g of HCl is present in 60 g of water.
- Assume that a ‘y’ gram of HCl is present in 50 g of water.
-Then
\[\begin{align}
  & \dfrac{40}{y}=\dfrac{60}{50} \\
 & y=33.33g \\
\end{align}\]

-Means 33.33 g of HCl is present in 50 g of water.
-Therefore total mass of the solution = 50 + 33.33 = 83.33 g.
-Total volume of the given solution in the question is 75 ml.
-Substitute the known values in the above equation to get the density solution.

\[\begin{align}
  & \text{Density=}\dfrac{\text{mass of the solution}}{\text{total volume of the solution}} \\
 & Density = \dfrac{83.33}{75} = 1.11g \\
\end{align}\]
-Therefore the density of the solution is 1.11 g.
So, the correct answer is “Option A”.

Note: Saturated HCl means, no more HCl is going to dissolve in a particular solution after adding some amount of HCl. But by heating the saturated solution we can dissolve more HCl into saturated solution. Then the resulting solution is called supersaturated solution.