Question

The concentration (w/w)% of a 200 g solution of common salt is 10%. If 20 g more water is mixed in it, then, its concentration becomes

• A. 10.10%
• B. 11.11%
• C. 9.99%
• D. 9.09%

Answer 1

The correct option is D 9.09%

Concentration (w/w)% of solution $=\frac{\text{Mass of solute}}{\text{Mass of solution}}\times 100$
$\Rightarrow 10=\frac{\text{Mass of solute}}{200}\times 100$
⇒ Mass of solute = 20 g
Mass of solvent = Mass of solution – Mass of solute
= 200 – 20
= 180 g
Mass of more water added to the solution = 20 g
∴ New mass of solvent = 180 + 20
= 200 g
∴ New mass of solution = Mass of solute + New mass of solvent
= 20 + 200
= 220 g
Concentration of (w/w)% of solution $=\frac{20}{220}\times 100$
=9.09%
Hence, the correct answer is option (d).