Question

(a) 5.85 g of NaCl is dissolved in 200 mL of water. What will be the molarity of this solution?
(b) Calculate the molarity of the solution obtained by dissolving 20.6 g NaBr in 500 mL of water.

• A. (a) $0.8$M (b) $0.4$ M
• B. (a) $0.6$M (b) $0.7$ M
• C. (a) $0.5$M (b) $0.4$ M
• D. none

Answer 1

Answer: (C)

(a) $0.5$M (b) $0.4$ M

Mole $=\frac{weight}{molecularweight}$

Molecular weight of $NaCl$ is 58.5

molarity of $NaCl$ = $\frac{mol}{volumeinL}$

=$\frac{5.85}{58.5\times 0.2}$ = 0.5M

Molecular weight of $NaBr$ is 103.

molarity of $NaBr$ = $\frac{mol}{volumeinL}$

= $\frac{20.6}{103\times 0.5}$ = 0.4M

Hence, option $C$ is correct.