A fixed mass of an ideal gas has a volume of 4.0 L at a pressure of 3.0 × 10⁵ Pa and a temperature of 27°C. If the temperature is raised to 127°C while the pressure is kept constant, what is the new volume of the gas?

At constant pressure, Charles's law gives $\frac{V_1}{T_1} = \frac{V_2}{T_2}$. Converting temperatures: $T_1 = 300$ K, $T_2 = 400$ K. Therefore $V_2 = V_1 \times \frac{T_2}{T_1} = 4.0 \times \frac{400}{300} = 5.3$ L. Option B results from using Celsius temperatures directly (4 × 127/30 is incorrect reasoning), option A from inverting the ratio, and option D from not converting to Kelvin and multiplying incorrectly.