A 20.0 mL solution containing 0.2 g impure
H2O2 reacts completely with 0.316 g of KMnO4
in acid solution. The purity of H2O2 (in %) is
_____________
(mol. wt. of H2O2 = 34; mol. wt. of
KMnO4 = 158)
Answer (integer)
85
Solution
5H<sub>2</sub>O<sub>2</sub> + 2MnO<sub>4</sub><sup>-</sup> + 6H<sup>+</sup> $\to$ 2Mn<sup>2+</sup> + 5O<sub>2</sub> + 8H<sub>2</sub>O
<br><br>Moles of KMnO<sub>4</sub> = ${{0.316} \over {158}}$ = 2 $\times$ 10<sup>-3</sup>
<br><br>Equivalents of H<sub>2</sub>O<sub>2</sub> = Equivalent of KMnO<sub>4</sub>
<br><br>= 2 × 10<sup>–3</sup> × 5 = 0.01
<br><br>Moles of H<sub>2</sub>O<sub>2</sub> = ${{0.01} \over 2}$ = 0.005
<br><br>Mass of pure H<sub>2</sub>O<sub>2</sub> = 0.005 × 34 = 0.170 gm
<br><br>Percentage purity = ${{0.17} \over {0.2}}$ $\times$ 100 = 85 %
About this question
Subject: Chemistry · Chapter: Some Basic Concepts of Chemistry · Topic: Mole Concept
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