Thermochemistry/Thermodynamics

Question 1

What is a system?

Answer 1

This is everything that is enclosed in a vessel and everything that you are observing.

Question 2

What is a surrounding?

Answer 2

This is everything asides from the system.

Question 3

What is the universe?

Answer 3

This includes both your system and the surroundings.

Question 4

What is the internal energy?

Answer 4

This is the total energy of the system.

Question 5

What happens in expansion?

Answer 5

There is a larger volume and the system is doing the work.

Question 6

What happens in compression?

Answer 6

There is a smaller volume and the surrounding is doing work on the system.

Question 7

What is pressure-volume work?

Answer 7

The change in volume with a constant external pressure.

Question 8

What 2 things do we look at when finding pressure-volume work?

Answer 8

1. ) Same system ( mols and pressure)

2. ) Different volume

Question 9

What happens to heat for an endothermic reaction?

Answer 9

The heat is being absorbed with a +Q.

Question 10

What happens to heat for an exothermic reaction?

Answer 10

The heat is being released with a -Q.

Question 11

What are the standard conditions for thermochemistry?

Answer 11

Pressure = 1 bar
Temperature = 273 K

Question 12

What is enthalpy?

Answer 12

This is a state function where the start and ends only matter not the pathway.

Question 13

How do you know if there are multiple steps to get to the final enthalpy?

Answer 13

The number of arrows to get to the final enthalpy determines the number of steps of the mechanism.

Question 14

What is a standard state?

Answer 14

This is the most stable form of the material under a given condition.

Question 15

What is Hess’s Law?

Answer 15

The total enthalpy change does not change no matter how many steps you have.

Question 16

What is the enthalpy of formation?

Answer 16

The change in enthalpy during the formation of 1 mole of a substance from its constituent elements.

Question 17

When is the heat of formation zero?

Answer 17

When looking at individual elements.

Question 18

What is the bond dissociation energy?

Answer 18

The energy required to break one mole of bonds.

Question 19

What are the assumptions?

Answer 19

1. ) Only looking at the net picture and other interactions are not taken into account.
2. ) Rest of the molecule affects the energy required to break the bonds.

Question 20

What is a soluble salt?

Answer 20

These salts dissociate 100% into water K»»»1 ions will only react if the “conjugate” they make is a weak acid or base.

Question 21

What are insoluble salts?

Answer 21

These are sparingly soluble salts that do not dissociate very much K«<1 solid salts are in equilibrium with ions.

Question 22

What happens with a large Ksp?

Answer 22

• More products are favoured
• More salts are dissociated
• With more soluble salts

Question 23

What happens with a small Ksp?

Answer 23

• More reactants favoured
• Less salt dissolves
• With a less soluble salt

Question 24

What is a supersaturated solution?

Answer 24

Q>K = shift left, reactants are favoured

Question 25

What is a saturated solution?

Answer 25

Q=K = No effect at equilibrium

Question 26

What is an unsaturated solution?

Answer 26

Q

Question 27

What factors affect solubility?

Answer 27

1. ) Temperature
2. ) Common-ion effect
3. ) Side reactions
4. ) pH

Question 28

What is a spontaneous reaction?

Answer 28

The reaction may require a jump start however no continuous external assistance is required a reaction may be slow and spontanous.

Question 29

Does spontaneous mean immediate?

Answer 29

No, spontaneous does not mean instantaneous.

Question 30

What is a nonspontaneous reaction?

Answer 30

Products can still be obtained but continuous external assistance is required.

Question 31

What is Gibb’s Free energy?

Answer 31

This identifies the variables of spontenaity.

Question 32

What is entropy?

Answer 32

The measure of randomness/disorder of the matter or energy in a system.

Question 33

What is the 3rd Law of Thermodynamics?

Answer 33

The entropy is 0 and there a perfect crystalline structure with perfect crystals and perfect alignment.

Question 34

What factors impact entropy?

Answer 34

1. ) Temperature
2. ) Physical state
3. ) Number of particles in the sample
4. ) Size complexity of the molecules

Question 35

How does entropy increase?

Answer 35

1. ) Solid -> Liquid -> Gas
2. ) Increase in temperature
3. ) More particles
4. ) Heavier atoms

Question 36

How does entropy decrease?

Answer 36

1.) Solid

Question 37

What is the 2nd Law of Thermodynamics?

Answer 37

The entropy of the universe will always increase.

Question 38

S > 0?

Answer 38

Spontaneous

Question 39

S = 0?

Answer 39

Equilibrium

Question 40

S < 0?

Answer 40

Non-spontaneous

Question 41

What is the Gibb’s free energy sign for the spontaneous reactions?

Answer 41

Negative

Question 42

What is the Gibb’s free energy sign for the nonspontaneous reactions?

Answer 42

Positive

Question 43

What happens to spontaneity when Q < K?

Answer 43

The forward reaction is spontaneous.

Question 44

What happens to spontaneity when Q = K?

Answer 44

The reaction is at equilibrium so the G = 0.

Question 45

What happens to spontaneity when Q > K?

Answer 45

The reverse reaction is spontaneous.