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Stoichiometric Calculations

One gram of ...

Question

One gram of $N a_{3} A s O_{4}$ is boiled with excess of solid $K I$ in the presence of strong $H C l$ . The iodine evolved is absorbed in $K I$ solution and titrated against $0.2 N$ hyposolution.
$A s O_{4}^{3 -} + 2 H^{+} + 2 I^{-} ⟶ A s O_{3}^{3 -} + H_{2} O + I_{2}$
Calculate the volume of thiosulphate hypo consumed, given that the atomic weight of $A s = 75$ amu.

A

48.1

mL

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B

38.4

mL

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C

24.7

mL

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D

30.3

mL

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Solution

The correct option is D $48.1$ mL
Change in oxidation state of $A s$ is $2$ .
Molecular weight of $N a_{3} A s O_{4}$ is $208$ g/mol. So, millimoles of the compound in $1$ g $= 4.81$ mmol
Millimoles of $I_{2}$ formed $= \frac{4.81}{2}$
Hyposolution oxidizes $I_{2}$ back to $I^{-}$ .
Volume of $0.2 N$ hyposolution required $= \frac{4.81}{2 \times 0.2} = 48.1$

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Similar questions

N a_{2} A s O_{4}

is boiled with excess of solid

K I

in presence of strong

H C l

. The iodine evolved is absorbed in

K I

solution and litrated against

0, 2 N

hypersolution. Assuming the reaction to be

A S O_{4}^{3 -} + 2 H^{+} + 2 I^{-} \to A s O_{3}^{2 -} + H_{2} O + I_{2}

.
Calculate the volume of thiosulphate hypo consumed. [Atomic weight of

A s = 75

K C l O_{3}

are dissolved in conc. HCl and the solution was boiled. Chlorine gas evolved in the reactions was in then passed through a solution of KI and liberated iodine was titrated with 100 ml of hypo. 12.3 ml of same hypo solution required 24.6 ml of 0.5 iodine for complete neutralization. Calculate % purity of

K C l O_{3}

K C l O_{3}

are dissolved in cone. HCl and the solution was boiled. Chlorine gas evolved in the reaction was then passed through a solution of KI and liberated iodine was titrated with 100 mL of hypo. 12.3 mL of same hypo solution required 24.6 mL of 0.5 N iodine for complete neutralization. Calculate % purity of

K C l O_{3}

2.5

g sample of copper is dissolved in excess of

H_{2} S O_{4}

100

0.02 M C u S O_{4} (a q)

10

0.02 M

C u S O_{4} (a q)

is mixed with excess of

K I

to show the following changes:

C u S O_{4} + 2 K I ⟶ K_{2} S O_{4} + C u I_{2}

2 C u I_{2} ⟶ C u_{2} I_{2} + I_{2}

The liberated iodine is titrated with hypo (

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

) which requires

V

0.1 M

hypo solution for its complete reduction.The amount of

I_{2}

liberated in the reaction of

10

0.02 M

solution with excess

K I

Q. An aqueous solution containing

0.10

K I O_{3}

(formula weight

= 214.0

) was treated with an excess of

K I

solution. The solution was acidified with

H C l

. The liberated

I_{2}

45.0

mL of thiosulphate solution to decolourise the blue starch iodine complex. Calculate the molarity of the sodium thiosulphate solution.

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