Chapter 7: Thermochemistry

Question 1

First Law of thermodynamics

Answer 1

ΔU = Q - W

ΔU = change in internal energy of the system
Q = heat added to the system
W = work done by the system

Question 2

Standard Conditions

Answer 2

25 C (298K), 1atm pressure and 1 M concentration

Question 3

STP

Answer 3

0 C (273K), 1 atm pressure

Question 4

heat transfer (no phase change)

Answer 4

q = m c ΔT

m = mass
c = specific heat of the substance
ΔT = change in termperature

Question 5

heat transfer (during phase change)

Answer 5

q = m c

m = mass
c = specific heat of the substance

Question 6

Generalized enthalpy of reaction

Answer 6

ΔHrxn = Hproducts - Hreactants

Question 7

Standard enthalpy of reaction

Answer 7

ΔHrxn = Σ ΔH f, products - Σ ΔH f, reactants

Question 8

Entropy

Answer 8

ΔS = Qrev / T

Qrev = heat that is gained or lost in a reversible process
T = temperature

Question 9

Bond breaking

Answer 9

Endothermic (takes energy to break bonds)

Question 10

Bond formation

Answer 10

Exothermic (releases energy to form bonds)

Question 11

Bond Dissociation: O=O

Answer 11

498 kJ/mol

Question 12

Bond Dissociation: C-H

Answer 12

415 kJ/mol

Question 13

Bond Dissociation: H-H

Answer 13

436 kJ/mol

Question 14

Second Law of thermodynamics

Answer 14

ΔS universe = ΔS system + ΔS surroundings

Question 15

Standard entropy of reaction

Answer 15

ΔSrxn = Σ ΔS f, products - Σ ΔS f, reactants

Question 16

Gibbs Free Energy

Answer 16

ΔG = ΔH - TΔS

Question 17

Standard Gibbs Free Energy of reaction

Answer 17

ΔGrxn = Σ ΔG f, products - Σ ΔG f, reactants

Question 18

Standard Gibbs Free Energy of reaction from equilibrium

Answer 18

ΔGrxn = - RT ln Keq

Question 19

Gibbs Free Energy from reaction quotient

Answer 19

ΔGrxn = ΔG^0rxn + RT ln Q