20 mL of hydrogen gas at -13°C is heated to 117°C at constant pressure. Find the new volume of hydrogen.

V₁ = Initial volume of the gas = 20 mL
T₁ = Initial temperature of the gas = -13°C = -13 + 273 = 260 K
T₂ = Final temperature of the gas = 117°C = 117 + 273 = 390 K
V₂ = Final volume of the gas =?

By Charles' Law:

$\dfrac{\text{V}$1}{\text{T}1} = \dfrac{\text{V}2}{\text{T}2}

Substituting the values :

$\dfrac{\text{20}}{260} = \dfrac{\text{V}$2}{390} \\[1em] \text{V}2 = \dfrac{20 \times 390}{260} \\[1em] \text{V}_2 = 30 \text{ mL}

∴ Final volume = 30 mL