Exam 1

Question 1

What determines whether a reaction will occur, and how fast it happens?

Answer 1

Thermodynamics and kinetics.

Question 2

What determines the directionality of a reaction?

Answer 2

Thermodynamic stability of the reactants and products.

Question 3

What determines the rate of a reaction?

Answer 3

Kinetic stability (or instability).

Question 4

Where is a reaction least stable?

Answer 4

Toward the top of a reaction path graph.

Question 5

What is a spontaneous reaction?

Answer 5

A reaction that occurs naturally under specific circumstances.

Question 6

What is a non-spontaneous reaction?

Answer 6

A reaction that must require continual energy input from an external source.

Question 7

Is ice melting at room temperature spontaneous or non-spontaneous?

Answer 7

Spontaneous.

Question 8

Is water freezing at room temperature spontaneous or non-spontaneous?

Answer 8

Non-spontaneous.

Question 9

Is water freezing at -10°C spontaneous or non-spontaneous?

Answer 9

Spontaneous.

Question 10

Is ice melting at -10°C spontaneous or non-spontaneous?

Answer 10

Non-spontaneous.

Question 11

What is a reversible process?

Answer 11

The system changes so that it returns to the state by exactly reversing the process.

Question 12

What is an irreversible process?

Answer 12

This process cannot be undone by exactly reversing the process. Most spontaneous processes are irreversible.

Question 13

What is thermodynamics the study of?

Answer 13

Study of energy and its transformations.

Question 14

What is thermochemistry the study of?

Answer 14

Study of the relations between chemical reactions and energy changes involving heat.

Question 15

What is a thermodynamically open system?

Answer 15

Energy and matter may move freely in and out.

Question 16

What is a thermodynamically closed system?

Answer 16

Matter may not move freely in and out, however, energy can.

Question 17

What is a thermodynamically isolated system?

Answer 17

Both matter and energy may not move in our out of the system.

Question 18

If a system loses energy, what gains energy?

Answer 18

Surroundings.

Question 19

If surroundings lose energy, what gains energy?

Answer 19

Systems.

Question 20

If ΔH > 0, is it endothermic or exothermic?

Answer 20

Endothermic. It absorbs energy.

Question 21

If ΔH < 0, is it endothermic or exothermic?

Answer 21

Exothermic. It releases energy.

Question 22

What is ΔH°f?

Answer 22

Standard enthalpy of formation. This determines the enthalpy change in which 1 mole of a substance is formed from pure elements in their standard states.

Question 23

What are the conditions for ΔH°f?

Answer 23

1 mole of substance.
Pure form of elements in their standard states.

Question 24

How do you calculate ΔH°rxn?

Answer 24

nΔH°(products) - nΔH°(reactants)

Question 25

What is S?

Answer 25

Entropy. The measure of how spread out or disperse the system energy is.

Question 26

Does spontaneity increase or decrease entropy (S) of a system?

Answer 26

Increase.

Question 27

For any spontaneous process, the entropy of the universe ________.

Answer 27

Increases.