Question

A gas is enclosed in a cylinder fitted with a light frictionless piston and maintained at atmospheric pressure. When 3300 kcal of heat is added to the gas, the volume is observed to increase slowly from 13.7m^3 19.7m^3.
a) Calculate the work done by the gas.
b) Calculate the change in internal energy of the gas.

Answer 1

Answer

given,

heat added to the gas,Q = 3300 kcal

initial volume, V₁ = 13.7 m³

final volume, V₂ = 19.7 m³

atmospheric pressure, P = 1.013 x 10⁵ Pa

a) Work done by the gas

    W = P Δ V

    W = 1.013 x 10⁵ x (19.7 - 13.7)

    W = 6.029 x 10⁵ J

b) internal energy of the gas = ?

  now,

 change in internal energy

  Δ U = Q - W

    Q = 3300 x 10³ cal

    Q = 3300 x 10³ x 4.186 J

    Q = 1.38 x 10⁷ J

now,

  Δ U = 1.38 x 10⁷  - 6.029 x 10⁵

  Δ U = 1.32 x 10⁷ J