If the temperature of 9.3 L of a gas at 6.5 ºC falls by 6.1 Cº, what is the new volume of the gas if the pressure is constant?

Question

Select one:

a. 9.10

b. 9.29

c. 0.0133

d. 45.74

Answer 1

Since pressure (P) is constant, you are dealing with Charles Law:

V1/T1 = V2/T2 where V is volume and T is temperature in degrees K

V1 = 9.3 L

T1 = 6.5ºC = 273 = 279.5K

V2 = ?

T2 = 6.5ºC - 6.1ºC = 0.4ºC + 273 = 273.4K

Solving for V2, we have...

V2 = (9.3 L)(273.4K)/279.5K

V2 = 9.10 L (answer a)

Answer 2

You will need to find the ideal gas law: do you remember it?

PV = nRT

In this problem, the constants are P, n, and R. Use the subscripts 1 and 2 to write two equations to describe the gas, before and after the temperature change:

PV₁ = nRT₁

PV₂ = nRT₂

Re-arrange these two equations in order to place the constants on one side, and the variables on the other side. Then you can make one equation based only on the variables. Try it and see what you get.

Hint: you will need to place your temperature in degrees Kelvin before calculating the answer. .