Q.A fixed mass of an ideal gas occupies a volume of $2\ \text{L}$ at a temperature of $27\,^\circ\text{C}$ when held at constant pressure. Find the volume it occupies when its temperature is raised to $127\,^\circ\text{C}$ at the same pressure. (All temperatures should be converted to the Kelvin scale before use.)

Given: $V_1 = 2\ \text{L}$ at $T_1 = 27 + 273 = 300\ \text{K}$; find $V_2$ at $T_2 = 127 + 273 = 400\ \text{K}$, pressure constant.

Using Charles's law, $\dfrac{V_1}{T_1} = \dfrac{V_2}{T_2}$:

Convert both temperatures to Kelvin first, then apply Charles's law, $V_1/T_1 = V_2/T_2$, directly to solve for $V_2$.

• Applying Charles's law directly with the Celsius temperatures ($27$ and $127$) instead of converting to Kelvin first -- the ratio only holds for absolute temperature.
• Inverting the ratio (computing $V_2 = V_1 T_1/T_2$) by mistake.