Question

What is the molarity of a solution of HCl which contains 49% by weight of solute and whose specific gravity is 1.41.
A. 15.25
B. 16.75
C. 18.92
D. 20.08

Answer 1

Hint There is a relationship between weight of an acid and specific gravity and it is as follows. Weight of an acid in one ml= (specific gravity) (percentage by weight)
There is a formula to calculate the molarity of the solution by using the following formula.
Molarity = $\dfrac{\text{weight of HCl in 1000 ml}}{\text{Molecular weight of HCl}}$

Complete step by step answer:
- In the question they have given to find the molarity of the HCl solution contains 49 % weight of the solute and its specific gravity is 1.41.
- Here HCl is the solute which is present in the water by 49%.
- We can find the weight of HCl in one ml by using the below formula.
Weight of hydrochloric acid (HCl) in one ml= (specific gravity) (percentage by weight) = (1.14) (0.49) = 0.6909 g/ml.
- We got the weight of HCl in one ml of the solution, by substituting it in the following formula we will get the molarity of the solution.
Molarity = $\dfrac{\text{weight of HCl in 1000 ml}}{\text{Molecular weight of HCl}}=\dfrac{690.9}{36.4}=18.92M$
(Molecular weight of the HCl = 36.4)
- Therefore the molarity of a solution of HCl which contains 49% by weight of solute and whose specific gravity is 1.41 is 18.92 M.

- So, the correct option is C.

Note: First we should calculate the weight of the acid in one ml and later we have to substitute the weight of the acid in 1000 ml in the formula to get the molarity of the HCl solution with the help of specific gravity.