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Standard XII

Chemistry

Oxides of Sulphur

4FeS + 7O2 ⟶ ...

Question

$4 F e S + 7 O_{2} ⟶ 2 F e_{2} O_{3} + 4 S O_{2}$
$C r_{2} O_{7}^{2 -} + 2 H^{+} + 3 S O_{2} ⟶ 2 C r^{3 +} + 3 S O_{4}^{2 -} + H_{2} O$
$1 g$ sample of $F e S$ was roasted with oxygen gas $S O_{2}$ thus formed required $10 m L$ of $0.05 M K_{2} C r_{2} O_{7}$ solution in acidic medium. Calculate percentage of $F e S$ in the sample. $(F e = 56, S = 32)$

1.2 %

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1.32 %

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1.5 %

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None of these

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Solution

The correct option is B $1.32 %$
$10 m L$ of $0.05 M K_{2} C r_{2} O_{7} = \frac{10 \times 0.05}{1000} m o l = 5 \times 10^{- 4} m o l$
$S O_{2} = 3 \times 5 \times 10^{- 4} m o l$
$p u r e F e S = 3 \times 5 \times 10^{- 4} m o l$
$= 15 \times 10^{- 4} \times 88 g$
$= 0.132 g in 10g impure F e S$
$= 1.32 %$

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Similar questions

0.32

g sample of impure

K I

was dissolved in

1.1

millimoles of

K_{2} C r O_{4}

and

25

mL of

5

H_{2} S O_{4}

. Iodine formed was expelled off by boiling and the solution is now mixed with excess of pure

K I

and

I_{2}

liberated again is completely reduced by

14

mL of

0.1 N N a_{2} S_{2} O_{3}

. Calculate percentage purity of impure

K I

sample. The reactions are given below:

2 C r O_{4}^{2 -} + 2 H^{+} ⟶ C r_{2} O_{7}^{2 -} + H_{2} O

C r_{2} O_{7}^{2 -} + 6 I^{-} + 14 H^{+} ⟶ 2 C r^{3 +} + 3 I_{2} + 7 H_{2} O

1.17 g

of an impure sample of oxalic acid was dissolved and made up to

200 m L

with water.

10 m L

of this solution in acid medium required

8.5 m L

of a solution of potassium permanganate containing

3.16 g p e r l i t r e

of oxidation. Calculate the percentage purity of oxalic acid.

Q. A

8 g m

sample of iron are containing

V %

(by wt) of iron

F e^{2 +}

was present in

1 L

solution. This solution required

V m L

of a

K M n O_{4}

solution for oxidation of

F e^{2 +}

in acidic medium. If in another titration

20 m L

of same

K M n O_{4}

is required, for oxidation of

20 m L H_{2} O_{2}

in acidic medium. Find volume strength of

H_{2} O_{2}

Q. A sample of

F e S O_{4}

and

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)

Q. 0.5 g sample of iron containing mineral mainly in the form of

C u F e S_{2}

was reduced suitably to convert all the ferric ions into ferrous ions

(F e^{3 +} ⟶ F e^{2 +})

and was obtained as solution. In the absence of any interfering radical, the solution required 42 mL of 0.01 M

K_{2} C r_{2} O_{7}

for titration. Calculate

%

C u F e S_{2}

in sample.

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4FeS+7O2⟶2Fe2O3+4SO2Cr2O2−7+2H++3SO2⟶2Cr3++3SO2−4+H2O1 g sample of FeS was roasted with oxygen gas SO2 thus formed required 10 mL of 0.05 M K2Cr2O7 solution in acidic medium. Calculate percentage of FeS in the sample. (Fe=56,S=32)

The correct option is B 1.32%10 mL of 0.05 M K2Cr2O7=10×0.051000 mol=5×10−4 molSO2=3×5×10−4 molpure FeS=3×5×10−4 mol=15×10−4×88 g=0.132 g in 10g impure FeS=1.32%