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Equilibrium Constant and Standard Free Energy Change

A 5g sample c...

Question

A 5g sample containing $F e_{3} O_{4} (F e O + F e_{2} O_{3})$ and an inert impurity is treated with excess of KI solution in the presence of dilute $H_{2} S O_{4}$ . The entire iron converted to Ferrous ion along with the liberation of Iodine. The resulting solution is diluted to 100 mL. 20 mL of the diluted solution requires $10 m L o f 0.5 M N a_{2} S_{2} O_{3}$ solution to reduce the iodine present. Calculate approximate percentage of $F e_{2} O_{3}$ ?

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Solution

$L e t t h e m o l e s o f F e_{3} O_{4} i s x . S o m o l e o f F e_{2} O_{3} (i n F e_{3} O_{4}) = x$
$e q o f F e_{2} O_{3} (i n F e_{3} O_{4}) = e q o f K I = e q o f I_{2} = e q o f N a_{2} S_{2} O_{3}$ .
or $2 x = 0.025$
or $x = 0.0125 m o l o f F e_{2} O_{3}$
$S o m a s s o f F e_{2} O_{3} = 0.0125 \times 160 = 2 g$
% $o f F e_{2} O_{3} = \frac{2}{5} \times 100 = 40$ %

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Similar questions

3.0 g

sample containing

F e_{3} O_{4}, F e_{2} O_{3}

and an inert impure substance is treated with excess of

K I

solution in presence of dilute

H_{2} S O_{4}

. The entire iron is converted to

F e^{2 +}

along with the liberation of iodine. The resulting solution is diluted to

100 m L

20 m L

of the dilute solution requires

11.0 m L

0.5 M N a_{2} S_{2} O_{3}

solution to reduce the iodine present. A

50 m L

of the diluted solution after complete extraction of iodine requires

12.8 m L

0.25 M K M n O_{4}

solution in dilute

H_{2} S O_{4}

medium for oxidation of

F e^{2 +}

. Calculate the percentage of

F e_{2} O_{3}

F e_{3} O_{4}

in the original sample.

1.249

g of a sample of pure

B a C O_{3}

C a C O_{3}

containing some

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was treated with dilute

H C l

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C O_{2}

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was precipitated, filtered and washed. The dried precipitate was dissolved in dilute sulphuric acid and diluted to

100

10

mL of this solution when treated with

K I

solution liberated iodine, which required exactly

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0.05 N

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50

ml of an aqueous solution of

H_{2} O_{2}

were treated with an excess of

K I

solution and dilute

H_{2} S O_{4}

. The liberated iodine required

20

0.1

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

solution for complete interaction. The concentration of

H_{2} O_{2}

50 m L

of an aqueous solution of

H_{2} O_{2}

was treated with an excess of

K I

solution and dilute

H_{2} S O_{4}

. The liberated iodine required

20 m L 0.1 N N a_{2} S_{2} O_{3}

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H_{2} S O_{2}

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Q. A solution of

0.2 g

of a compound containing

C u^{2 +}

C_{2} O_{4}^{2 -}

ions on titration with

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K M n O_{4}

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H_{2} S O_{4}

22.6

mL of the oxidant.

The resultant solution is neutralised with

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