please determine the pressure of butane gas (C4H10) in the gas box at 30oC.

Question

Consider a gas cylinder with volume of 31200dm³ for storing and shipping pure butane gas (C₄H₁₀), it is known that the pressure in the bottle is 41kPa at 15^oC.

(c) In order to reduce the pressure in the gas cylinder, a technician suggested to reduce the volume of the gas cylinder storing the same amount of gas. Please comment on his suggestion and state your reasons.

(d) In order to use the butane gas (C₄H₁₀), the gas cylinder is linked with a 109200dm3 gas box and left for some time in order to attain equilibrium, please determine the pressure of butane gas (C₄H₁₀) in the gas box at 30^oC.

Answer 1

Ok Jenny, here we go...

Recall the dm³ is the same as liter (L) so I'll use L

(c) If you want to reduce the pressure of the gas in the cylinder, you would NOT reduce the volume of the cylinder as that would INCREASE the pressure. To reduce the pressure, you would INCREASE the volume of the cylinder.

(d) The original volume was 31,200 L, the original pressure was 41 kPa and the original temperature was 15ºC. The new volume will be 31,200 L + 109,200 L = 140,400 L. The final temperature is 30ºC and we need to find the final pressure.

We can use the Combined Gas Law: P1V1/T1 = P2V2/T2

P1 = initial pressure = 41kPa

V1 = initial volume = 31,200 L

T1 = initial temperature in Kelvin = 15 + 273 = 288K

P2 = final pressure = ?

V2 = final volume = 140,400 L

T2 = final temperature in Kelvin = 30 + 273 = 303K

P1V1/T1 = P2V2/T2

(41)(31,200)/288 = (P2)(140,400)/303

P2 = (41)(31,200)(303) / (288)(140,400)

P2 = 9.59 kPa