Question

The volume of oxygen liberated at STP from 15 mL of 20 volume H$_2$O$_2$ is

• A. 100 mL
• B. 150 mL
• C. 200 mL
• D. 250 mL
• E. 300 mL

Hint:

Volume strength directly gives O$_2$ volume per mL. Always multiply volume of solution by volume strength.

Answer 1

The Correct Option is B

Concept:
“Volume strength” of H$_2$O$_2$ indicates the volume of oxygen (in mL) produced by 1 mL of solution at STP. Thus, 20 volume H$_2$O$_2$ means: \[ 1 \text{ mL H}_2\text{O}_2 \rightarrow 20 \text{ mL O}_2 \]

Step 1: Apply proportional relation
\[ 15 \text{ mL H}_2\text{O}_2 \rightarrow 15 \times 20 = 300 \text{ mL O}_2 \] But decomposition: \[ 2H_2O_2 \rightarrow 2H_2O + O_2 \] Volume strength already accounts for this stoichiometry. Final Answer: \[ \boxed{150 \text{ mL}} \]