On expanding isothermally from 2L to 4L, an ideal gas does 6J of work, as the pressure drops from 2 atm to 1 atm. By how much must it expand to do an additional 6J of work?

1
On expanding isothermally from 2L to 4L, an ideal
gas does 6J of work, as the pressure drops from
2 atm to 1 atm. By how much must it expand to
do an additional 6J of work?
A It must expand an additional 2L, to reach 6L
B It must double again, to 8L C It must
increase four-fold, to 16L D It can do no more
work, as it has reached 1 atm. E Cannot
determine without knowing T
2
An ADIABATIC PROCESS is one in which no heat
transfer occurs. Q0.If we expand a gas from VA
to VB adiabatically, what will be the final
pressure?

• A More than PB
• B Less than PB
• C Equal to PB
• D cannot determine

Lets do the math
3
Review questions For the constant pressure
ideal gas process shown, The change in internal
energy U of the gas is A nCv?? B nCp?? C
0 D cannot determine
4
If the gas is monatomic and ideal, for the
constant pressure process shown, the change in
internal energy can also be expressed as A
p?V B C D
(use a paper pencil. Hint what is ?T?)
5
For the cyclic process shown, W is
For ONE cycle
For the cyclic process shown, Q is
For the cyclic process shown, ?U is

• A 0, because its a loop
• B p0V0
• C - 2p0V0
• D 2 p0V0
• E 6 p0V0

Monatomic, Ideal
6
Along which sides is heat added to the gas?

• A 12 only
• B 23 only
• C 34 only
• D 12 23
• E 12 34

7
Along which sides is heat removed from the gas?

• A 34 only
• B 41 only
• C 34 41
• D heat is not removed on any side

8
We know heat is added 12 and 23. Heat is removed
on 34 and 41. Is more heat added, or removed?

• A added
• B removed
• C the same amount of heat is removed as was
  added

9
We know heat is added 12 and 23. Heat is removed
on 34 and 41. Is more heat added, or removed?

• A added
• B removed
• C the same amount of heat is removed as was
  added

Heat is NOT a state variable. It is a process
variable. More heat was added than removed,
because the gas did work and energy is conserved!
10
We saw that there is always heat rejected in a
thermodynamic cycle Qc