# An expandable balloon volume calculation

## An expandable balloon contains 3.50 dm3 of helium at 101. kPa and 23.0oC.

**What volume will the balloon occupy when the pressure drops to 85.0 kPa and the temperature is 10.0oC?**

Answer:

3.98dm³

Explanation:

Using combined gas law equation:

P1V1/T1 = P2V2/T2

Where;

P1 = initial pressure (kPa)

P2 = final pressure (kPa)

V1 = initial volume (dm³)

V2 = final volume (dm³)

T1 = initial temperature (K)

T2 = final temperature (K)

According to the provided information in this question:

V1 = 3.5dm³

V2 = ?

P1 = 101 kPa

P2 = 85.0 kPa

T1 = 23.0°C = 23 + 273 = 296K

T2 = 10.0°C = 10 + 273 = 283K

Using P1V1/T1 = P2V2/T2

101 × 3.5/296 = 85 × V2/283

353.5/296 = 85V2/283

Cross multiply

296 × 85V2 = 353.5 × 283

25,160V2 = 100,040.5

V2 = 100,040.5 ÷ 25,160

V2 = 3.98dm³