Question

On complete combustion of 0.96 g of an organic compound, 0.88 g of carbon dioxide and 0.1 g of water are produced. What is the percentage composition of carbon in the compound?

• A. 22\%
• B. 18\%
• C. 16\%
• D. 20\%
• E. 25\%

Hint:

To calculate the percentage composition of an element in a compound after combustion, first find the mass of the element from the products (COâ‚‚ and Hâ‚‚O) and then divide by the total mass of the compound.

Answer 1

Answer: (E)

To find the percentage composition of carbon, we need to first calculate the amount of carbon in the compound.
1. Moles of carbon in COâ‚‚: The molar mass of COâ‚‚ is 44 g/mol, and it contains 1 mole of carbon per mole of COâ‚‚.
Moles of COâ‚‚ produced = \( \frac{0.88 \, \text{g}}{44 \, \text{g/mol}} = 0.02 \, \text{mol} \)
Since each mole of COâ‚‚ contains 1 mole of carbon, moles of carbon in COâ‚‚ = 0.02 mol.
2. Mass of carbon in COâ‚‚:
The mass of carbon in COâ‚‚ = \( 0.02 \, \text{mol} \times 12 \, \text{g/mol} = 0.24 \, \text{g} \).
3. Mass of hydrogen in Hâ‚‚O:
The molar mass of Hâ‚‚O is 18 g/mol, and it contains 2 moles of hydrogen per mole of water.
Moles of Hâ‚‚O produced = \( \frac{0.1 \, \text{g}}{18 \, \text{g/mol}} = 0.0056 \, \text{mol} \)
The mass of hydrogen in Hâ‚‚O = \( 0.0056 \, \text{mol} \times 2 \times 1 \, \text{g/mol} = 0.0112 \, \text{g} \).
4. Mass of carbon in the compound: The total mass of the organic compound is 0.96 g. The mass of carbon is found from the COâ‚‚ product, which is 0.24 g.
5. Percentage composition of carbon:
\[ \text{Percentage of carbon} = \frac{0.24 \, \text{g}}{0.96 \, \text{g}} \times 100 = 25\% \] Thus, the correct answer is (E) 25\%.