Question

0.224 g of an organic compound on complete combustion gives 0.126 g of water. What is the percentage composition of hydrogen in the compound?

• A. $6.25%$
• B. $35%$
• C. $12.50%$
• D. $25%$

Hint:

While calculating hydrogen percentage, always use the relation that 2 g of hydrogen is present in 18 g of water.

Answer 1

The Correct Option is A

Step 1: Calculate mass of hydrogen in water formed.
Molar mass of water $= 18$
Mass of hydrogen in $18$ g of water $= 2$ g
Step 2: Find hydrogen present in 0.126 g of water.
\[ \text{Mass of H} = \frac{2}{18} \times 0.126 = 0.014\ \text{g} \]
Step 3: Calculate percentage of hydrogen.
Mass of compound taken $= 0.224$ g
\[ %\text{H} = \frac{0.014}{0.224} \times 100 \]
\[ %\text{H} = 6.25% \]
Step 4: Conclusion.
The percentage composition of hydrogen in the compound is $6.25%$.