A sample of hydrogen bromide gas occupies 45.5 cm3 at 30.0 °C and 30.0 in.Hg.What is the final Celsius temperature if the volume is 45.5 cm3 at 15.0 in.Hg?

Question

Quizplus · Accepted Answer

We can use the combined gas law to solve this problem:

(P1V1/T1) = (P2V2/T2)

P1 = 30.0 in.Hg = 1.015 atm (using a conversion factor)
V1 = 45.5 cm3
T1 = 30.0 °C + 273.15 = 303.15 K
P2 = 15.0 in.Hg = 0.508 atm (using a conversion factor)
V2 = 45.5 cm3
T2 = ?

Plugging in the values and solving for T2:

(1.015 atm x 45.5 cm3)/(303.15 K) = (0.508 atm x 45.5 cm3)/(T2)
T2 = (0.508 atm x 45.5 cm3)/(1.015 atm) x (303.15 K)
T2 = 135.0 K

Converting this temperature back to Celsius:

T2 = 135.0 K - 273.15
T2 = -138.15 °C

The final Celsius temperature is -138.15 °C, which is closest to choice A (-121 °C).

A Sample of Hydrogen Bromide Gas Occupies 45