Thermochemistry Flashcards Preview

MCAT Physical Sciences > Thermochemistry > Flashcards

Flashcards in Thermochemistry Deck (25):
1

Closed System

Exchange energy, but not matter

2

Isolated System

Nothing exchanged

3

Open System

Allows for exchange of energy and matter

4

Isobaric

Constant Pressure

5

Isothermal

Constant temperature (system must gain or lose energy to maintain)

6

Isochoric

Constant Volume, no net pressure-volume work

7

Adiabatic Process

No heat transferred to or from the system by surroundings

8

Heat

Transferrable Energy
q = mcΔt when there is no phase changes

9

Exothermic Reaction

Net release of energy into surroundings (-)

10

Endothermic Reaction

Net absorption of energy from surroundings (+)

11

Enthalpy

Total heat content of a system at a constant pressure (ΔH)

12

Hess's Law

Enthalpy change of an overall reaction is equal to the sum of the standard heats of formation of the products minus the sum of the standard heats of formation of the reactants
ΔH = ΔH(prod) - ΔH(reac)

13

Entropy

ΔS = q(rev)/ T
Entropy increases during spontaneous reactions

14

Gibbs Free Energy

Energy available in system to do work (ΔG)

15

Gibbs Helmholtz Equation

ΔG = ΔH - TΔS
ΔG = ΔG0 + RT ln Q

16

When will a reaction be spontaneous?

ΔG < 0

17

What happens if ΔG is zero?

ΔG = TΔS

18

What are the only temperature dependent states?

When both ΔH and ΔS have the same sign

19

What happens when ΔH is positive, but ΔS is negative?

The reaction is nonspontaneous at all temperatures

20

What happens when ΔS is positive and ΔH is negative?

The reaction is spontaneous at all temperatures

21

If both ΔH and ΔS are positive?

The reaction is spontaneous only at high temperatures

22

What does the rate of a reaction depend on?

The activation energy, no ΔG

23

Reaction Quotent

ΔG0 = -RT ln K(eq)

24

State Function

Depends only on the initial and final states of a system, not the path

25

Standard Free Energy (ΔG0)

ΔG calculated at 1 atm and 0 K