Oleum and its % labelling MCQ - Practice Questions & Answers

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Volume Strength of H2O2 Solution and Hardness of Water

Volume Strength of H2O2 Solution :

The concentration of H₂O₂ is usually represented in terms of volume, if a sample of H₂O₂ is labeled as 'X' volume, it means that 1 volume of H₂O₂ solution gives 'X' volumes of O₂ gas at STP on complete decomposition. Consider the decomposition of H₂O₂ as:
$\\\mathrm{2H_{2}O_{2}\overset{\Delta }{\rightarrow}\, 2H_{2}O\, +\, O_{2}}\\2\mathrm{\, \times \, 34Kg\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: 22.4\ L\, at\, STP}$
As 22400 ml of O₂ gas is liberated by 68 g of H₂O₂solution. So X ml of O₂ gas will be liberated by:
$\mathrm{=\frac{68X}{22400}\, =\, \frac{17X}{5600}\ g\ of\, H_{2}O_{2}}$
It means that (17X / 5600) g of H₂O₂ will be present in 1 ml of solution.
1000 ml of solution contains H₂O₂
$\frac{17X}{5600}\, \times\,1000 =\, \frac{17X}{5.6}$
Strength (g L^-1) = Normality x Equivalent wt.

$\\\mathrm{\frac{17X}{5.6}=\,N\times\frac{34}{2}(n-factor\, of\, H_{2}O_{2}\, =\, 2})\\\\\mathrm{X\,=\, 5.6\, \times\, N}$
that is, Volume strength of H₂O₂ = 5.6 x Normality

Hardness of Water :
The hardness of water is due to the presence of bicarbonates, chlorides and sulphates of calcium and magnesium bicarbonates causes temporary hardness while chlorides and sulphates cause permanent hardness. The extent of hardness is called degree of hardness. It is defined as the number of parts by weight of calcium carbonate present In one million parts by weight of water that is, in ppm (milligrams per litre) of CaCO₃

$\mathrm{Hardness\, of\, water\, =\, \frac{gm\, of\, calcium\, carbonate}{10^{6} gm\, of\, water}}$