You visited us 1 times! Enjoying our articles? Unlock Full Access!

Byju's Answer

Standard XII

Chemistry

Stoichiometric Calculations

A solution co...

Question

A solution contains $2.52$ g of a reductant per litre. $25$ mL of this solution of the reductant requires $20$ mL of $0.01 M K M n O_{4}$ in acidic medium for oxidation. Find the molecular weight of the reductant given that each of two atoms which undergo oxidation per molecule of the reductant suffers an increase in the oxidation state by one unit.

Open in App

Solution

Increase in the oxidation state of each reductant is $1$ .
Net increase in the oxidation state of two atoms in one molecule of reductant is $2$ .
Net decrease in the oxidation state of $K M n O_{4}$ in acidic medium is $5$ .
Thus, $2$ moles $K M n O_{4} \equiv 5$ moles reductant.
Let $M$ g/mol be the molar mass of the reductant.

Number of moles of $K M n O_{4} = \frac{20}{1000} \times 0.01 M = 2 \times 10^{- 4}$ moles

Number of moles of reductant $= \frac{5}{2} \times 2 \times 10^{- 4}$ moles $= 5 \times 10^{- 4}$ moles

Mass of reductant $= 5 \times 10^{- 4}$ moles $\times M$
But $2.52$ g of reductant is present in $1 L$ .

Mass of reductant in $25$ mL $= \frac{25}{1000} \times 2.52 = 0.063$ g

Hence, $0.063$ g $= 5 \times 10^{- 4}$ moles $\times M$

or, $M = 126 g m o l^{- 1}$
Hence, the molecular weight is $126$ g/mol.

Suggest Corrections

Similar questions

Q. A solution contains

2.52

g/L of a reductant.

25

mL of this solution required

20

mL of

0.01

K M n O_{4}

in acid medium for oxidation. Find the molar mass of reductant. Given that each of the two atoms, which undergo oxidation per molecule of reductant suffer an increase in oxidation state by one unit.

25

mL of a solution containing ferrous sulphate and ferric sulphate, acidified with

H_{2} S O_{4}

is reduced by metallic zinc. The solution requires

34.25

mL of

0.1 N

solution of

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

for oxidation. However, before reduction with zinc,

25

mL of same solution requires

22.45

mL of same

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

. Calculate the weight of

F e_{2} (S O_{4})_{3}

present in gram per litre of the solution (in nearest integer).

Q. If

10

ml of

H_{2} O_{2}

solution requires

25

ml of

\frac{N}{20} K M n O_{4}

for complete oxidation in acidic medium, then the mass (in g) of available

O_{2}

per litre present in the solution is:

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}

Join BYJU'S Learning Program