How many millilitres of 20 volume $\mathrm{H}_2 \mathrm{O}_2$ solution is needed to react completely with…

How many millilitres of 20 volume $\mathrm{H}_2 \mathrm{O}_2$ solution is needed to react completely with $500 \mathrm{~mL}$ of acidified $1 \mathrm{~N} \mathrm{KMnO}_4$, solution?
  1. 224
  2. 280
  3. 140
  4. 56

Solution

Given, Normality of $\mathrm{KMnO}_4\left(N_1\right)=1 \mathrm{~N}$ Volume of $\mathrm{KMnO}_4\left(V_1\right)=500 \mathrm{~mL}$ Normality of $\mathrm{H}_2 \mathrm{O}_2\left(N_2\right)=\frac{\text { Volume strength }}{5.6(\text { eq. mass })}=\frac{20}{5.6}$ $ \left(N_2\right)=3.5 $ Now, $\quad N_1 V_1\left(\mathrm{KMnO}_4\right)=N_2 V_2\left(\mathrm{H}_2 \mathrm{O}_2\right)$ $ \begin{aligned} & 1 \times 500=3.57 \times V_2 \\ & \therefore \quad V_2=\frac{500}{a-0}=140 \mathrm{~mL} \end{aligned} $

Asked in: AP EAMCET 2017 (26 Apr Shift 1)

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