Question

An 80.0-L volume of an ideal gas in a cylinder with a piston is at a pressure of 3.0atm. While the system is held at constant temperature, enough weight is placed on the piston to increase the external pressure to 10.0atm. For the resulting process, determine q(heat) and w(work) in units of kJ, and with proper signs. (Note: 1 L atm = 101.3 J)

Answer 1

Constant temperature.

Hence, Apply Boyle's law to find the final volume:

V₂ = (P1V1) / (P2)

V₂ = (3 atm x 80 L) / (10 atm)

V₂ = 24 L

Therefore, Work done is given by:

W = -P_ext (V₂ - V₁)

W = -(10 atm) x (24 - 80) L

W = 560 L.atm

W = (560 L.atm ) x (101.3 J)

W = 56728 J ---------------- (Answer)

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From First law of thermodynamics:

Q = ΔU + W

Here, constant temperature, so ΔU = 0

Q = W

Q = 56728 J ---------------- (Answer)