Q12 / 160 · TS EAMCET 2015 · Chemistry

What is the weight (in gram) of $\mathrm{Na}_2 \mathrm{CO}_3$ (molar mass $=106)$ present in $250 \mathrm{~mL}$ of its $0.2 \mathrm{M}$ solution?

  • A
    0.53
  • Correct answer
    B
    5.3
  • C
    1.06
  • D
    10.6

Solution

Molarity $$ \begin{aligned} & =\frac{\text { Weight of solute }}{\text { Molecular weight of solute }} \times \frac{1000}{\text { volume }(\text { in mL })} \\ & 0.2=\frac{\text { Weight of solute }}{106} \times \frac{1000}{250} \\ & \therefore \quad \text { Weight of solute }=\frac{0.2 \times 106 \times 250}{1000}=5.3 \mathrm{gm} \end{aligned} $$

Hence, the correct answer is option: 'B'.

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