Part B An ideal gaseous reaction (which is a hypothetical gaseous reaction that
ID: 906531 • Letter: P
Question
Part B
An ideal gaseous reaction (which is a hypothetical gaseous reaction that conforms to the laws governing gas behavior) occurs at a constant pressure of 50.0 atm and releases 65.6 kJ of heat. Before the reaction, the volume of the system was 6.40 L . After the reaction, the volume of the system was 2.60 L .
Calculate the total internal energy change, U, in kilojoules.
Express your answer with the appropriate units.
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State functions versus path functions
The change in internal energy, U, is a state function because it depends only on the initial and final states of the system, and not on the path of change. In contrast, q and w are path functionsbecause they depend on the path of change and not just the initial and final states of the system.
Part C
An ideal gas (which is is a hypothetical gas that conforms to the laws governing gas behavior) confined to a container with a massless piston at the top. (Figure 2) A massless wire is attached to the piston. When an external pressure of 2.00 atm is applied to the wire, the gas compresses from 4.90 to 2.45 L . When the external pressure is increased to 2.50 atm, the gas further compresses from 2.45 to 1.96 L .
In a separate experiment with the same initial conditions, a pressure of 2.50 atm was applied to the ideal gas, decreasing its volume from 4.90 to 1.96 L in one step.
If the final temperature was the same for both processes, what is the difference between q for the two-step process and q for the one-step process in joules?
Express your answer with the appropriate units.
U =Explanation / Answer
1. W = 50( 6.4 - 2.6) lit.atm = 190 lit.atm = 19.25 kJ ....[ Sign is positive as work is done on the system.]
dU = dQ + dW
= -65.6 kJ + 19.25 kJ ...[Heat is released; sign of dQ is negative.]
= -46.35 kJ
2. When temperature does not change , dU = 0.
In this condition, q = w = pdV
For the first system,
q = 2(4.9-2.45) + 2.5(2.45 - 1.96)
= 6.125 lit.atm
For the second system,
q= 2.5(4.9-1.96)
=7.35 lit.atm
difference = 7.35-6.125
=1.225 lit.atm
= 124 J