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Redox Reactions

In a quality ...

Question

In a quality control analysis for sulphur impurity, $5.6$ g of steel sample was burnt in a stream of oxygen. Sulphur was converted into $S O_{2}$ gas. The $S O_{2}$ was then oxidized to sulphate by using $H_{2} O_{2}$ solution to which had been added $30$ mL of $0.04 M N a O H$ . The equation for reaction is as follows:

$S O_{2} (g) + H_{2} O_{2} (a q) + 2 O H^{-} (a q) ⟶ S O_{4}^{2 -} (a q) + 2 H_{2} O (l)$

$22.48$ mL of $0.024 M H C l$ was required to neutralize the base remaining after oxidation reaction. Calculate the percentage of sulphur in the given sample.

A

0.16 %

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B

0.14 %

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C

0.22 %

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D

None of the above

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Solution

The correct option is B None of the above
Meq. of alkali added $= 30 \times 0.04 = 1.2$
Meq. of alkali left $= 22.48 \times 0.024 = 0.54$
$∴$ Meq. of alkali used for $S O_{2}$ and $H_{2} O_{2} = 1.2 - 0.54 = 0.66$

$∴$ Mass of alkali used $= \frac{0.66 \times 40}{1000} = 0.0264$ g

$∵ 80$ g $N a O H$ reacts with $64$ g of $S O_{2}$ .

$∴ 0.0264$ g $N a O H$ reacts with $\frac{64 \times 0.0264}{80} = 0.021$ g

Now, $∵ 64$ g $S O_{2}$ required $= 32$ g $S$

$∴ 0.021$ g $S O_{2}$ required $= \frac{32 \times 0.021}{64} = 0.0105$ g

Percentage of $S = \frac{0.0105}{5.6} \times 100 = 0.1875 %$

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Similar questions

Q. A sample of steel weighing

0.6

g and containing

S

as an impurity was burnt in a stream of

O_{2}

S

was converted to its oxide

S O_{2}

S O_{2}

was then oxidized to

S {_{4}}^{2 -}

H_{2} O_{2}

solution containing

30

0.04

22.48

0.024

H C l

was required to neutralize the base remaining after oxidation. The

%

S

in the sample is:

F e S O_{4}

F e C_{2} O_{4}

was dissolved in dilute sulphuric acid. The complete oxidation of the reaction mixture required 40 mL of N/15

K M n O_{4} .

after the oxidation, the reaction mixture was reduced by Zn and

H_{2} S O_{4} .

On using the same solution of

K M n O_{4}

to oxidize the resulting solution, 25 mL was required. Calculate the ratio of equivalents of Fe in oxalate and Fe(II) sulphate. (Fe: 56)

1

g of a moist sample of a mixture of

K C l O_{3}

K C l

was dissolved in water and made upto

250

25

mL of this solution was treated with

S O_{2}

to reduce chlorate into chloride and the excess

S O_{2}

was boiled off. When the total chloride was precipitated,

0.1435

g of AgCI was obtained. In another experiment,

25

mL of the original solution was treated with

30

0.2

F e S O_{4}

F e S O_{4}

37.5

0.08

N solution of an oxidizing agent for complete oxidation. The molar ratio of chlorate and chloride in the given mixture

F e^{2 +}

C I O_{3}^{-}

according to equation,

C l O_{3}^{-} + 6 F e^{2 +} + 6 H^{+} \to C I^{-} + 6 F e^{3 +} + 3 H_{2} O

Q. 32 g of a sample of

F e S O_{4}

7 H_{2} O

were dissolved in dilute sulphuric acid and water and its volume was made up to 1 litre. 25 mL of this solution required 20 mL of 0.02 M

K M n O_{4}

solution for complete oxidation. Calculate the mass % of

F e S O_{4}

7 H_{2} O

12

g of an impure sample of arsenious oxide was dissolved in water containing

7 .5

g of sodium bicarbonate and the resulting solution was diluted to

250

25

mL of this solution was completely oxidized by

22.4

mL of solution of iodine.

25

mL of this iodine solution reacted with same volume of a solution containing

24.8

g of sodium was completely oxidized by

22.4 m L

of a solution thiosulphate

(N a_{2} S_{2} O_{3} 5 H_{2} O)

in one litre. Calculate the percentage of arsenious oxide in the sample. (Atomic mass of

A s = 75

)

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