Oxygen Gas...moles...!!!!?

Question

Calculate the number of moles of oxygen gas produced from the complete catalyzed decomposition of 5.60ml sample of a 3.5% solution of H2O2. The density of the 3.5% solution of H2O2 is 1.01 g/ml.

Answer 1

The reaction is 2 H2O2 >>> 2 H2O + O2

First convert ml solution to grams solution by multiplying by density, then to grams H2O2 by multiplying by % H2O2, then finally to grams oxygen by the factor 32/34. This comes from (2 x 16)/[(2 x 1) + (2 x 16)], then divide by 32 to get moles oxygen gas (O2)

[5.6ml x 1.01 g/ml x 0.035 x (32/34)]/32g/mol = 0.00582 mole

Answer 2

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Answer 3

Hai Thanu§hree,

The reaction involved is:

2H2O2 ----> 2H2O + O2
Means, each mole of H2O2 gives 1/2 mole of O2.

So, let us find the number of moles of H2O2 in the solution.

Mass of H2O2 solution = Volume * Density = 5.60 * 1.01 = 5.656 g
Mass of H2O2 in the solution = Concentration of H2O2 solution * Mass of H2O2 solution = 3.5% * 5.656 = 0.19796 g

Moles of H2O2 in solution = Mass of H2O2 / Molecular Wt. of H2O2

Molecular Wt. of H2O2 = 2*Atomic Wt. of H + 2*Atomic Wt. of O

Atomic Wt. of H = 1.00794 g·mol−1
Atomic Wt. of O = 15.9994 g·mol−1
Molecular Wt. of H2O2 = 2*1.00794 + 2*15.9994 = 34 g·mol−1 .....(approximated)

Moles of H2O2 = 0.19796/34

Moles of O2 liberated = (1/2)*(0.19796/34) = 0.19796/68 = 0.0029 moles

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