Q22 / 160 · TS EAMCET 2022 (20 Jul Shift 2) · Chemistry

If $2 \mathrm{~g}$ of $\mathrm{NaOH}$ is dissolved to make $200 \mathrm{ml}$ solution at $25^{\circ} \mathrm{C}$, the molarity $(\mathrm{M})$ at $90^{\circ} \mathrm{C}$ is

  • Correct answer
    A
    $\mathrm{M} < 0.25$
  • B
    $0.5>M>0.25$
  • C
    $\mathrm{M}=0.25$
  • D
    $0.5 < \mathrm{M} < 1.0$

Solution

Concentration of the solution at $20^{\circ} \mathrm{C}$ $$ =\frac{\mathrm{n}}{\mathrm{V}}=\frac{2 / 40}{200 / 1000}=0.25(\mathrm{M}) \quad[\mathrm{Mw} \text { of } \mathrm{NaOH}=40] $$ As temp. increases the volume of the solution increases but the no. of moles remains the same. Hence, concentration of the solution decreases.

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

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