JAMB Chemistry 2019 Paper

Concept:Use the stoichiometry of the reaction to determine the volumes of gases consumed and produced, since volumes of gases react in the ratio of their coefficients at constant temperature and pressure.Explanation:Equation: $2\mathrm{CO} + \mathrm{O}_2 \rightarrow 2\mathrm{CO}_2$From the equation, $2$ volumes of $\mathrm{CO}$ react with $1$ volume of $\mathrm{O}_2$ to give $2$ volumes of $\mathrm{CO}_2$.$50\,\mathrm{cm}^3$ of $\mathrm{CO}$ requires only $\frac{50}{2} = 25\,\mathrm{cm}^3$ of $\mathrm{O}_2$.Volume of $\mathrm{CO}_2$ produced $= 50\,\mathrm{cm}^3$.Excess $\mathrm{O}_2 = 100 - 25 = 75\,\mathrm{cm}^3$.Total volume of resulting mixture $= 50 + 75 = 125\,\mathrm{cm}^3$.Answer:$125\,\mathrm{cm}^3$