JAMB Chemistry 2024 Paper

Concept:Combustion stoichiometry uses the balanced chemical equation to convert the given mass of oxygen into moles of carbon dioxide produced.Explanation:Write the balanced equation for the complete combustion of ethanol:$$\mathrm{C_2H_5OH} + 3\mathrm{O_2} \rightarrow 2\mathrm{CO_2} + 3\mathrm{H_2O}$$From the equation, $3$ moles of $\mathrm{O_2}$ produce $2$ moles of $\mathrm{CO_2}$.Calculate the moles of oxygen present using $n = \frac{\text{mass}}{\text{molar mass}}$:$$n(\mathrm{O_2}) = \frac{6\text{ g}}{32\text{ g mol}^{-1}} = 0.1875\text{ mol}$$Apply the mole ratio $3:2$ to get the moles of $\mathrm{CO_2}$:$$n(\mathrm{CO_2}) = 0.1875 \times \frac{2}{3} = 0.125\text{ mol}$$Answer:A. 0.125