Question

A sample h2o2 solution labelled as "28 volume" has density of 265 g/l. mark the correct option(s) representing concentration of same solution in other units :

Answer 1

The density mentioned in the question should be 26.5 g/Litre instead of 265 g/ litre.

Answer: -

"28 vol" H₂O₂ means that 1 litre volume of H₂O₂ will give off 28 litre volumes of O₂ at 1 atm and 25 C that is 298 K.

Using the relation for oxygen gas

PV = nRT

Number of moles n =$\frac{PV}{RT}$

                                 = $\frac{1 x 28}{0.0821 x 298}$

                                  = 1.144 moles of O₂

Now the decomposition reaction for hydrogen peroxide is

2H₂O₂ →2H₂O + O₂

So 1 mole of O₂ is formed from 2 moles of H₂O₂

1.144 mole of O₂ is formed from 2 x 1.144 moles of H₂O₂

                                                   = 2.288 moles of H₂O₂

Since 2.288  moles is present in 1 litre,

Molarity = 2.288 M

Molality = Molarity x density

             = 2.288 M x 26.5 g / litre

             = 60.6 g / Litre