Question

Ideal gas expands isothermally from 20 dm³ to 25 dm³ at constant pressure of 1.5 bar; then work done in dm³ bar will be ______.

Options

• −1.5

• −5

• −7.00

• −7.5

Answer 1

Ideal gas expands isothermally from 20 dm³ to 25 dm³ at constant pressure of 1.5 bar; then work done in dm³ bar will be −7.5.

Explanation:

Given: P_ext = 1.5

V₁ = 20 dm³

V₂ = 25 dm³

ΔV = V₂ − V₁

= 25 − 20

= 5 dm³

For expansion against a constant external pressure, the work done (W) is calculated using the following formula:

W = −P_ext × ΔV

= −1.5 × 5

= −7.5 dm³ bar

∴ The work done in dm³ bar is −7.5.