Question

How many grams of $NaCl$ will have to be dissolved in 50 gm of ${\text{H}}_{\text{2}}\text{O}$ to make its 20% solution (by mass)?

• A. 12.5 gm
• B. 25.5 gm
• C. 10.0 gm
• D. 20 gm

Answer 1

Answer: (A)

12.5 gm

Let $x$ $gm$ of $NaCl$ is added.

Now, $\frac{x}{50+x}\times 100=20$

$\Rightarrow x=12.5$ $gm$

Thus, 12.5 grams of $NaCl$ will have to be dissolved in 50 g of $H_{2}O$.