A gas is allowed to expand in a well-insulated container against a constant external pressure of 2 . 5 atm…

A gas is allowed to expand in a well-insulated container against a constant external pressure of 2.5 atm from an initial volume of 2.50 L to a final volume of 4.50 L. The change in internal energy ΔU of the gas in joules will be
  1. 1136.25 J.
  2. -500 J.
  3. -505 J.
  4. +505 J.

Solution

ΔU=q+w
For adiabatic process, q=0
∴      ΔU=w
=-P⋅ΔV
= -2.5 atm×4.5-2.5L
= -2.5×2 L-atm
= -5×101.3 J
=-506.5 J
≈-505 J

Asked in: MHT CET Full Test 11

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