Question

A fresh $H_2{O}_2$ solution is labelled 11.2V. This solution has the same concentration as a solution which is:

• A. 3.4% (w/v)
• B. 3.4% (v/v)
• C. 3.4% (w/w)
• D. none of these

Answer 1

The correct option is A

3.4% (w/v)

Volume strength refers to the volume of oxygen gas liberated from that solution. 11.2 V means that 11.2 litres of oxygen released.

The balanced reaction is:

$2H_2{O}_2\to 2H_{2}O+O_2$

2 moles release 22.4 litres, 1 mole would release 11.2 litres.

So, the molarity of the given solution is 1 M.

Now, % (w/v) $=\frac{\text{weight of solute in g}}{\text{100 mL solution}}$

Since molarity is expressed per litre of solution, or 1000 mL, we can find the mass in the given molarity and divide it by 10 to get the mass in 100 mL.

$=\text{Molarity}\times mol.wt.\text{of solute}\times \frac{1}{10}$

$=1\times 34\times \frac{1}{10}=3.4\%$