Question

The teacher instructed three students A, B and C respectively to prepare a 50% (mass by volume) solution of sodium hydroxide ($NaOH$). A dissolved 50g of $NaOH$ in 100 ml of water, B dissolved 50g of $NaOH$ in 100g of water while C dissolved 50g of $NaOH$ in water to make 100 ml of solution. Which one of them has made the desired solution?

• A. A
• B. B
• C. C
• D. All of the above

Answer 1

The correct option is C C

'C' has made the desired solution
Mass by volume $\%=\frac{\text{Mass of solute}}{\text{Volume of solution}}\times 100$
$=\frac{50}{100}\times 100$
$=50\%$ mass by volume
50 % Mass by volume means 50g of NaOH is dissolved in 100ml of solution. So C makes the solution. A has taken 100 ml of water itself. Hence, A does not make the desired solution. B has taken 100 gm of water. Thus, for B also, the solution will not be $50\%$ mass by volume.