Question

You perform the following steps:

1. Heat up a balloon that contains 4 mol of helium gas from 293K to 353K....

Problem 2. You perform the following steps: 1. Heat up a balloon that contains 4 mol of helium gas from 293K to 353K. (pressure inside of oven is2 atm) 2. Very slowly squeeze the balloon until the volume decreases from 0.5L to 0.25L 3. Grab the balloon, put it in a container that does not allow it to change its shape, and while keeping it in there, cool back down to 293K. a. What is the purpose of doing step 2 slowly? b. Draw what the PV diagram of the system would look like for this set of processes. What is the total AE for the system? c. d. What is the total work done by the system?

Answer 1

a) The reason for performing step 2 very slowly is to keep the process reversible.

b) Since it is given that process 1 takes place in oven at 2 atm pressure, hence its a isobaric process AB and the volumes can be calculate using formula T1/V1 =T2/V2. V1 is the volume at T=293 and V2 at 353 respectively. putting V2= 0.5L we get V1=0.42L. Now the volume is reduced keeping the temprature constant BC at 353K. therefor using P1V1=P2V2 where V1=0.5L and V2=0.25L and P1=2atm. we get P2=4atm. now finally the pressure is reduced by keeping volume constant i.e. isochorically CD. therefore P1/T1=P2/T2 where P1=4atm and T1=353 and T2= 293 we get P2 = 3.32atm. hence the graph drawn is as shown below. C)

D)