# Chemistry 104 Worksheet

1. A steel tank containing 02 is heated - slightly., As it is heated, the density of the O2 gas
1. a increases
2. decreases
3. stays the same? Explain where the heat goes.

2. A container fitted with a piston containing 02 is heated slightly. As it is heated, the density of the O2 gas
1. increases
2. decreases
3. stays the same?
Explain where the heat goes.

3.
4. What is work?
• How is, it defined for an expanding gas?
Compressing gas?
What is the equation for work for a gas?
Why are each of the terms necessary?

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5. Explain why the "foamy stuff" that comes out of a fire extinguisher is cold.

6. In Dr. Yerkes demonstration with the dry ice in a sealed bag, the bag expanded, doing PV work. Where did the energy for this work come from?

7. A gas absorbs 100 J of heat and is simultaneously compressed by an external pressure of 1.5 atm from 8.0 L to 2.0 L in volume. What is δE for the gas?

• How much work is done?
How much heat is transferred?
9. Now redo #10, this time using an external pressure of 1.00 atm.
• How much work is done?
How much heat is transferred?
What is the change in internal energy?
10. In a system where 4 L of gaseous reactant produces 3.5 L of gaseous products, the surroundings have to work on the system because
1. the surroundings have to drive the reaction
2. the change in volume requires the surroundings to do work by compressing the system
3. the reaction is actually doing work on the surroundings by decreasing the pressure
4. the volume change in the system has no bearing on the work the surroundings does on the system

11. You initially have a gas at P=3.0 atm and V=5.5 L. The gas is contained in a piston with an external pressure such that the final volume is 10.5 L. Calculate the work. Be sure that the sign for work is correct.

12. You have the same conditions as in the question above but you go about getting to the final state in two steps. The first step is a volume of 7.0 L. The second step gets you to a volume of 10.5 L. Calculate the total work done in this case.

13. Again, you have the same initial and final conditions but this time you expand the gas in two steps with the middle step being at 8.0 L. What is the work?

14. In questions 10, 11. and 12 the work calculated is different for each condition. Why isn't work a state function? Why does work increase with the number of steps? Which two-step process yielded more work? Why is this? When is Pexternal=Pinternal (answer for both the reversible and irreversible cases)?