Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MCAT-GENERAL CHEMISTRY > Thermodynamics > Flashcards

Thermodynamics Flashcards

You may prefer our related Brainscape-certified flashcards:
MCAT flashcards AP® Chemistry flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

the laws of thermodynamics underlie any even in which ______ is transformed

A

energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

the Zeroth Law

A

if two systems are both in thermal equilibrium with a third system, then the two initial systems are in thermal equilibrium with one another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

if systems are in thermal equilibrium, what does this imply about their temperatures?

A

their temperatures must be the same

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

the First Law

A

the total energy of the universe is constant, energy may be transformed from one form to another, but it cannot be created or destroyed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

an isolated system has a constant ______

A

amount of matter and ENERGY: no transformation of the energy is possible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how can a system increase its overall energy?

A

if work is put into its system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what happens when energy flows into a system from the surroundings?

A

the energy of the system increases (+) and the energy of the surroundings decrease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what happens when energy flows out of a system into the surroundings?

A

the energy of the system decreases (-) and the energy of the surroundings increase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

enthalpy, H

A

the measure of the heat energy that is released or absorbed when bonds are broken and formed during a reaction that’s run at constant pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

when a bond is formed, energy is:

A

released, enthalpy change is negative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

when a bond is broken, energy is:

A

put into the bond, enthalpy change is positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

heat of reaction

A

enthalpy change, delta H

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

when is enthalpy change negative, exergonic?

A

when the products of a chemical reaction have stronger bonds than the reactants, so that more energy is released in the making of product bonds than was put in to break chemical bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how do you calculate enthalpy change?

A

enthalpy of products - enthalpy of reactants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

exothermic

A

energy is released overall from the system, enthalpy change is negative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

endothermic

A

energy is absorbed into the system, enthalpy change is positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

standard conditions

A

298K (25 degrees Celsius), pressure is 1 atm, all solids and liquids are assumed to be pure, solutions are at a concentration of 1 M

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

standard heat of formation

A

the amount of energy required to make one mole of a compound from its constituent elements in their natural or standard state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what does it mean if standard heat of formation is a positive value?

A

an input of heat is required to make the compound from its constituent elements

20
Q

what does it mean if standard heat of formation is a negative value?

A

making the compound from its elements gives off energy

21
Q

Hess’s law

A

if a reaction occurs in several steps, then the sum of the energies absorbed or given off in all the steps will be the same as that for the overall reaction

22
Q

what does it mean that enthalpy is a state function?

A

the enthalpy change is independent of the pathway of reaction

23
Q

what happens to the value of enthalpy change if reaction is reversed?

A

the sign of enthalpy change is reversed too

24
Q

what happens to the value of enthalpy change if an equation is multiplied by a coefficient?

A

the enthalpy change must be multiplied by that same value

25
Q

enthalpies can be viewed as the energy stored in the chemical bonds of a compound that denotes how much energy is required to:

A

break the bond homolytically

26
Q

how do you calculate the enthalpy change of reaction?

A

sum of BDE of bonds broken - sum of BDE of bonds formed

27
Q

second law of thermodynamics

A

the disorder of the universe increases in a spontaneous process

28
Q

entropy

A

disorder or randomness, S

29
Q

what is the sign of entropy change if randomness increases and order decreases in a reaction?

A

positive

30
Q

what is the sign of entropy change if randomness decreases and order increases in a reaction?

A

negative

31
Q

what is the value of enthalpy change in a reverse reaction?

A

the same magnitude as that of the forward reaction but with opposite signs

32
Q

can reactions in which entropy decreases occur?

A

yes, but it would require either an input in energy or else it must gain energy from making more stable bonds

33
Q

The Third Law

A

absolute zero is a state of zero-entropy

34
Q

Gibbs free energy (delta G)

A

the energy that’s available (free) to do work from a chemical reaction

35
Q

what is the spontaneity of a reaction determined by?

A

changes in enthalpy and in entropy, included by G

36
Q

what is the formula for Gibbs free energy

A

G=H-TS

37
Q

what does it mean if Gibbs free energy is negative?

A

it is spontaneous in the forward direction

38
Q

what does it mean if Gibbs free energy is zero

A

the reaction is at equilibrium

39
Q

what does it mean if Gibbs free energy is positive

A

it is nonspontaneous in the forward direction

40
Q

if delta G is positive for a reaction, then what is the value of delta G for the reverse reaction?

A

it would be the same magnitude but opposite sign, so that the reverse reaction is spontaneous

41
Q

what does entropy depend on?

A

temperature; increased temperature=entropy has greater significance

42
Q

the universe tends towards…

A

increasing disorder (positive S) and stable bonds (negative H), a favourable condition of S and H will result in spontaneous processes

43
Q

what is the delta G of the overall reaction?

A

the difference between the energy of the products and the energy of the reactants

44
Q

the activation energy determines:

A

the kinetics of the reaction: it is the extra energy the reactants are required to overcome

45
Q

thermodynamics predicts:

A

the spontaneity and the equilibrium of reaction, not the rates (kinetics)

46
Q

microscopic reversibility

A

the reverse reaction has the same magnitude for all thermodynamic values but of the opposite sign, and the same reaction pathway but in reverse (mirror images)

47
Q

what is different for forward and reverse reactions?

A

activation energy

MCAT-GENERAL CHEMISTRY (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions