When gases are heated from 20 to 40ºC at constant pressure, their volumes — States of Matter and Gaseous State Chemistry Question

💡 Solution & Explanation

# Solution: Volume Change of Gases at Constant Pressure **Given Information:** - Initial temperature: $T_1 = 20°C = 293$ K - Final temperature: $T_2 = 40°C = 313$ K - Pressure remains constant **Apply Charles's Law:** At constant pressure, volume is directly proportional to absolute temperature: $$\frac{V_1}{T_1} = \frac{V_2}{T_2}$$ **Calculate volume ratio:** $$\frac{V_2}{V_1} = \frac{T_2}{T_1} = \frac{313}{293} = 1.068$$ **Result:** $$V_2 = 1.068 \times V_1$$ The volume increases by approximately **6.8%** (or roughly **7%**). **Why option D is correct:** The volume increases in direct proportion to the absolute temperature increase. Since temperature increased from 293 K to 313 K, the volume must increase proportionally according to the ideal gas law at constant pressure.