# 25 g of an unknown hydrocarbon upon burning produces 88 g of CO2 and 9 g of H2O. This unknown hydrocarbon contains:

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25 g of an unknown hydrocarbon upon burning produces 88 g of CO2 and 9 g of H2O. This unknown hydrocarbon contains:
1. 20 g of carbon and 5 g of hydrogen
2. 22 g of carbon and 3 g of hydrogen
3. 24 g of carbon and 1g of hydrogen
4. 18 g of carbon and 7g of hydrogen

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Correct Answer - Option 3 : 24 g of carbon and 1g of hydrogen

Calculation:

Let the hydrocarbon is CxHy

${{\rm{C}}_{\rm{x}}}{{\rm{H}}_{\rm{y}}} + {{\rm{O}}_2} \to {\rm{xC}}{{\rm{O}}_2} + \frac{{\rm{y}}}{2}{\rm{\;}}{{\rm{H}}_2}{\rm{O}}$

Mole of water H2O = 18.01528 g/mol

Mole of carbon dioxide CO2 = 44.01 g/mol

Weight of hydrogen (H) = 1.00784 u

Weight of carbon (C) = 12.0107 u

Weight of carbon = $\frac{{88}}{{44}} \times 12 = 24\;g$

Weight of Hydrogen = $\frac{9}{{18}} \times 1 = 0.5\;g \approx 1$

Therefore the unknown hydrocarbons contains 24 g of carbon and 1 g of hydrogen.

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