The final temperature of the gas : 84.6 °C
Further explanation
Charles's Law
When the gas pressure is kept constant, the gas volume is proportional to the temperature
[tex]\tt \dfrac{V_1}{T_1}=\dfrac{V_2}{T_2}[/tex]
T₁=initial temperature=25°C+273=298 K
V₁=initial volume=80 cm³
volume increment : 20% x 80 cm³=16 cm³
V₂ = Final volume = 80 cm³ + 16 cm³ = 96 cm³
So the final temperature :
[tex]\tt T_2=\dfrac{V_2\times T_1}{V_1}\\\\T_2=\dfrac{96\times 298}{80}\\\\T_2=357.6~K=84.6^oC[/tex]
