A gas expands in volume from 26.7 to 89.3 mL at constant temperature.

Calculate the work done (in joules) if the gas expands

(a) against a vacuum,

(b) against a constant pressure of 1.5 atm,

(c) against a constant pressure of 2.8 atm.

(1L⋅atm=101.3J)

(a) 0 J

(b) - 9.5 J

(c) - 18 J

Explanation:

A gas expands in volume from 26.7 to 89.3 mL at constant temperature. The change in volume is:

ΔV = 89.3 mL - 26.7 mL = 62.6 mL = 0.0626 L

The work done (w) can be calculated using the following expression.

w = - P * ΔV

where,

P is the pressure

(a) against a vacuum (P = 0)

w = - P * ΔV = - 0 atm * 0.0626 L = 0 atm. L = 0 J

(b) against a constant pressure of 1.5 atm

w = - P * ΔV = - 1.5 atm * 0.0626 L * (101.3 J/1 atm. L) = - 9.5 J

(c) against a constant pressure of 2.8 atm

w = - P * ΔV = - 2.8 atm * 0.0626 L * (101.3 J/1 atm. L) = - 18 J