Question

10. Hydrogen peroxide (H2O2: M = 34 g mol-1) is a powerful oxidising agent that is used in concentrated solution in rocket fuel systems and in dilute solution as in hair bleach. An aqueous solution of H2O2 is 30 % by mass and has a density of 1.11 g cm-3. Express the concentration of the solution in terms of: (i) Molality​

Answer 1

The concentration of the H2O2 solution can be expressed in terms of molality, which is the amount of solute (in moles) dissolved per kilogram of solvent. To calculate the molality, we determine the amount of solute in moles and the mass of solvent in kilograms.

Step-by-step explanation:

The concentration of a solution can be expressed in terms of molality which is the amount of solute (in moles) dissolved per kilogram of solvent. To express the concentration of the H2O2 solution in terms of molality, we need to determine the amount of solute in moles and the mass of solvent in kilograms.

Given that the H2O2 solution is 30% by mass, we can calculate the mass of the solute:

• Mass of solute = 30% * Mass of solution
• = 30% * 1 kg
• = 0.3 kg

Next, we convert the mass of the solute to moles using the molar mass of H2O2:

• Moles of solute = Mass of solute / Molar mass of H2O2
• = 0.3 kg / 34 g mol-1
• = 0.00882 mol

Finally, we calculate the molality:

• Molality = Moles of solute / Mass of solvent in kg
• = 0.00882 mol / 1 kg
• = 0.00882 mol/kg

Answer 2

The molality of solution=12.605 m

Step-by-step explanation:

We are given that

Molar mass of Hydrogen peroxide, M=34 g/mol

Density of solution,
`\rho=1.11gcm^(-3)`

30% Means mass of solute (Hydrogen peroxide)=30 g

Mass of solvent =100-30=70 g

Total mass of solution, m=100 g

Number of moles of solute=
`(given\;mass)/(molar\;mass)`

Using the formula

Number of moles of hydrogen peroxide=
`(30)/(34)`

Now, molality of solution

`m=(number\;of\;moles\;of\;solute)/(mass\;of\;solvent)* 1000`

`m=(30)/(70* 34)* 1000`

`m=12.605 m`

Hence, the molality of solution=12.605 m