A fixed-pressure gas expansion (ideal gas): A sample occupies 2 litres at N.T.P. At what temperature will it occupy 4 litres if the pressure is kept constant?

Introduction / Context:
For an ideal gas at constant pressure, volume is directly proportional to absolute temperature (Charles’s law). Doubling the volume requires doubling the temperature in kelvins.

Given Data / Assumptions:

• Initial state at N.T.P. ≈ 273 K and 1 atm.
• V1 = 2 L, V2 = 4 L, P constant.
• Ideal-gas behavior; container can expand.

Concept / Approach:
Use V ∝ T at constant P: V2/V1 = T2/T1. With V2/V1 = 2, T2 = 2 * T1.

Step-by-Step Solution:
T1 = 273 K (N.T.P.).Compute T2 = 2 * 273 = 546 K.Convert to Celsius: 546 − 273 = 273°C.

Verification / Alternative check:
Check proportionality: doubling V at constant P must double T in kelvins, confirming 273°C.

Why Other Options Are Wrong:
273 K indicates no change; 100°C and 200°C do not double the absolute temperature from 273 K.

Common Pitfalls:
Doubling Celsius temperature instead of absolute temperature; misreading NTP as 300 K.

Final Answer:
273°C