Midterm

Question 1

1st law of thermodynamics

Answer 1

Energy is conserved; it isn’t created or destroyed, it just changes forms (e.g. heat and work)

Question 2

2nd law of thermodynamics

Answer 2

Indicates whether or not a reaction will be spontaneous based on the maximization of entropy and the minimization of enthalpy

Question 3

3rd law of thermodynamics

Answer 3

In a perfectly ordered crystal, as the temp approaches 0, so does entropy

It does NOT say that if the temp is 0 K, S = 0 K

Question 4

James Joule experiment

Answer 4

Found that heat is created by mechanical energy

Estimated the mechanical equivalent of heat

Question 5

Old view of heat

Answer 5

Heat thought to be a conserved property called a calorie

Question 6

Ideal gas

Answer 6

Hypothetical gas whose molecules do not interact with each other

Question 7

Intensive vs extensive properties

Answer 7

Intensive: doesn’t change with amt of sample (e.g. boiling point, color)

Extensive: changes with the amount of sample (e.g., mass, volume)

Question 8

3 types of systems

Answer 8

Open: can exhange BOTH matter and energy with surroundings

Closed: can only exchange energy with surroundings – completely closed to matter

Isolated: can’t exchange either matter nor energy with surroundings

Question 9

State vs path function

Answer 9

State function: doesn’t matter how you get to end result

Path function: value depends on how the change is made (e.g. slowly vs gradually)

Question 10

Sudden/irreversible rxn vs gradual/reversible rxn

Answer 10

Sudden: fast

Gradual: slow
- NOTE: reversible work is theoretical – would need infinite time steps – but is shows the theoretical max work
- Reversible work is greater than irreversible work – requires more work for sustained effort

Question 11

Enthalpy equation

Answer 11

H = E + PV

Question 12

+ vs - H values

Answer 12

+ H –> endothermic (system gains heat energy)

• H –> exothermic (system loses heat energy)

Question 13

Does nature prefer more or less microstates

Answer 13

More – nature tends to prefer disorder over order

Question 14

Gibbs free energy

Answer 14

Measure of how much useful E is available to do work in a system at constant temp and pressure

Question 15

+ vs - vs 0 G

Answer 15

• G –> rxn is SPONTANEOUS ; spontaneity tends to occur when there’s more entrpoy. entropy is in the outflow of the G eqn, so more entropy means negative G

+ G –> rxn is not spontaneous

0 G –> rxn is at equilibrium

Question 16

Partial pressure eqn

Answer 16

mole fraction * total pressure