A science class puts a balloon containing 1.25 l of air at 101 kpa into a bell jar. using an air pump, the class removes some of the air in the jar, causing the balloon to expand to a volume of 2.25 l. assuming a constant temperature, what is the new pressure inside the jar?

The first thing you should know in this case is the following definition:

PV = nRT

Then, as the temperature is constant, then:

PV = k

Then, we have two states:

P1V1 = k

P2V2 = k

We can then equalize both equations:

P1V1 = P2V2

Substituting the values:

(1.25) * (101) = (2.25) * (P2)

Clearing P2:

P2 = ((1.25) * (101)) / (2.25) = 56.11Kpa

answer:

the new pressure inside the jar is 56.11Kpa