Q19 / 55 · KVPY 2020 (SA) · Chemistry

Strength of a H2O2 solution is labeled as 1.79 N. Its strength can also be expressed as closest to

  • A
    20 volume
  • B
    5 volume
  • Correct answer
    C
    10 volume
  • D
    15 volume

Solution

2H2O2aq.⟶2H2Oℓ+O2g

General Solution :- 

It is a common trend that n-factor H2O2 is
taken as '2' 

By the definition of volume strength of H2O2 if we consume 1ℓ of 1 N H2O2 in the above equation we are using 1 gram equivalent of
H2O2≡0.5 moles of H2O2 (by using n-factor =2)

This will produce 14 moles of O2 gas at N.T.P.

≡14×22.4=5.6ℓ of O2 gas

i.e. 1ℓ,1 N H2O2 solution gives 5.6ℓ O2 at N.T.P

Hence 1 N≡5.6 'vol.' H2O2 solution

In the given question it is 1.76 N H2O2 solution Hence volume strength =5.6×1.79≃10 volumes

Suggested Solution :- 

2H2O2aq.⟶2H2Oℓ+O2g

The above equation is a classic example of
disproportionation of H2O2, hence we should take n-factor of H2O2=1

1ℓ,1 N H2O2 solution ≡1 Gm equivalent of H2O2

≡1 mole of H2O2

This will produce 12 moles of O2 gas at N.T.P.

=12×22.4=11.2ℓ of O2 gas

i.e. 1ℓ,1 N H2O2 solution gives 11.2ℓ of O2 gas at N.T.P.

Hence 1 N≡11.2 'vol' H2O2 solution 

In the given question it is 1.79 NH2O2 solution

Hence, volume strength =1.79×11.2≃10 volumes

Suggested Answer is option (A)

Hence, the correct answer is option: 'C'.

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