WAEC Chemistry 2022 Paper

Concept:The ideal gas equation connects the pressure, volume, temperature, and number of moles of a gas.Here, oxygen is treated as an ideal gas.Explanation:List the given data: $P = 10\ \mathrm{atm}$, $V = 8.2\ \mathrm{dm}^3$, $T = 320\ \mathrm{K}$.The gas constant is $R = 0.082\ \mathrm{atm\ dm^3\ mol^{-1}\ K^{-1}}$.Use the ideal gas equation: $PV = nRT$.Rearrange the equation to solve for the number of moles: $n = \frac{PV}{RT}$.Substitute the given values into the formula: $n = \frac{10 \times 8.2}{0.082 \times 320}$.Simplify the numerator: $10 \times 8.2 = 82$.Simplify the denominator: $0.082 \times 320 = 26.24$.Divide to find $n$: $n = \frac{82}{26.24} = 3.125$.Hence, the number of moles of oxygen required is approximately $3.13\ \mathrm{mol}$.This matches option C.Answer:C. 3.13