A 2.0g sample containing MnO₂ is treated with HCl liberating Cl₂. The Cl₂ gas is passed into a solution of Kl and 60.0mL of 0.1M Na₂S₂O₃ is required to titrate the liberated iodine. The percentage of MnO₂ in the sample is_______. (Nearest integer)

[Atomic masses (in u) Mn = 55; Cl = 35.5; O = 16, I = 127, Na = 23, K = 39, S = 32]

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Payal Gupta | Contributor-Level 10

2 months ago

$M n O_{2} + 4 H C l \to M n C l_{2} + C l_{2} + 2 H_{2} O$

$\begin{array}{l} C l_{2} + 2 K l \to 2 K C l + I_{2} \\ I_{2} + 2 N a_{2} S_{2} O_{3} \to 2 N a l + N a_{2} S_{4} O_{6} \end{array}$

Here, meq of MnO₂ = meq of Na₂S₄O₆

$\frac{w}{E} \times 1000 = M \times n - f a c t o r \times V$

$\frac{w}{87 / 2} \times 1000 = 0.1 \times 1 \times 60$

Mass of MnO₂ in sample = 0.261 g

Percentage of MnO₂ in sample = $\frac{0.261}{2} \times 100$

= 13.05%

<math> <mrow> <mi>M</mi> <mi>n</mi> <msub> <mrow> <mi>O</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msub> <mo>+</mo> <mn>4</mn> <mi>H</mi> <mi>C</mi> <mi>l</mi> <mo>→</mo> <mi>M</mi> <mi>n</mi> <mi>C</mi> <msub> <mrow> <mi>l</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msub> <mo>+</mo> <mi>C</mi> <msub> <mrow> <mi>l</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msub> <mo>+</mo> <mn>2</mn> <msub> <mrow> <mi>H</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msub> <mi>O</mi> </mrow> </math>   <math> <mtable columnalign="left"> <mtr> <mtd> <mrow> <mi>C</mi> <msub> <mrow> <mi>l</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msub> <mo>+</mo> <mn>2</mn> <mi>K</mi> <mi>l</mi> <mo>→</mo> <mn>2</mn> <mi>K</mi> <mi>C</mi> <mi>l</mi> <mo>+</mo> <msub> <mrow> <mi>I</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msub> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <msub> <mrow> <mi>I</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msub> <mo>+</mo> <mn>2</mn> <mi>N</mi> <msub> <mrow> <mi>a</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msub> <msub> <mrow> <mi>S</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msub> <msub> <mrow> <mi>O</mi> </mrow> <mrow> <mn>3</mn> </mrow> </msub> <mo>→</mo> <mn>2</mn> <mi>N</mi> <mi>a</mi> <mi>l</mi> <mo>+</mo> <mi>N</mi> <msub> <mrow> <mi>a</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msub> <msub> <mrow> <mi>S</mi> </mrow> <mrow> <mn>4</mn> </mrow> </msub> <msub> <mrow> <mi>O</mi> </mrow> <mrow> <mn>6</mn> </mrow> </msub> </mrow> </mtd> </mtr> </mtable> </math>               Here, meq of MnO2 = meq of Na2S4O6 <math> <mrow> <mfrac> <mrow> <mi>w</mi> </mrow> <mrow> <mi>E</mi> </mrow> </mfrac> <mo>×</mo> <mn>1</mn> <mn>0</mn> <mn>0</mn> <mn>0</mn> <mo>=</mo> <mi>M</mi> <mo>×</mo> <mi>n</mi> <mo>−</mo> <mi>f</mi> <mi>a</mi> <mi>c</mi> <mi>t</mi> <mi>o</mi> <mi>r</mi> <mo>×</mo> <mi>V</mi> </mrow> </math>                               <math> <mrow> <mfrac> <mrow> <mi>w</mi> </mrow> <mrow> <mn>8</mn> <mn>7</mn> <mo>/</mo> <mn>2</mn> </mrow> </mfrac> <mo>×</mo> <mn>1</mn> <mn>0</mn> <mn>0</mn> <mn>0</mn> <mo>=</mo> <mn>0</mn> <mo>.</mo> <mn>1</mn> <mo>×</mo> <mn>1</mn> <mo>×</mo> <mn>6</mn> <mn>0</mn> </mrow> </math>                              Mass of MnO2 in sample = 0.261 gPercentage of MnO2 in sample =   <math> <mrow> <mfrac> <mrow> <mn>0</mn> <mo>.</mo> <mn>2</mn> <mn>6</mn> <mn>1</mn> </mrow> <mrow> <mn>2</mn> </mrow> </mfrac> <mo>×</mo> <mn>1</mn> <mn>0</mn> <mn>0</mn> </mrow> </math> = 13.05%

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