Chapter 16: Thermodynamics

Question 1

what is the first law of thermodynamics?

Answer 1

the total energy-mass of the universe is constant. however, this does not tell us anything about the direction of change in the universe

Question 2

what happens when two objects of different temperatures come into contact?

Answer 2

heat spontaneously flows from the hotter object to the colder object

Question 3

microstates

Answer 3

a specific configuration of all the locations and energies of atoms or molecules that make up a system. the number of microstates creates chaos

Question 4

what happens to S when temperature changes?

Answer 4

S increases as temperatures rises

Question 5

what happens to S when physical states and phase changes?

Answer 5

S increases as a more ordered phase changes to a less ordered phase

Question 6

What happens to S in a dissolution of a solid or a liquid?

Answer 6

S of a dissolved solid or liquid is usually greater than the S of the pure solute, however, the extent depends upon the nature of the solute and solvent

Question 7

What happens to S in a dissolution of a gas?

Answer 7

a gas becomes more ordered when it dissolves in a solid or liquid

Question 8

what happens to S in atomic size or molecular complexity?

Answer 8

in similar substances, increased mass relate directly to entropy.

Question 9

what is entropy?

Answer 9

the measure of the chaos or disorder in a system

Question 10

entropy of a system

Answer 10

the entropy change that occurs when all reactants and products are in their standard states

Question 11

formula for the entropy of a system

Answer 11

sum of products - sum of reactants

Question 12

second law of thermodynamics

Answer 12

the total entropy of an isolated system can never decrease over time, and is constant if and only if all processes are reversible. isolated systems spontaneously evolve toward thermodynamic equilibrium, the state with maximum entropy

Question 13

formula to know if a reaction is spontaneous

Answer 13

S - H/T

a positive value indicates it is spontaneous

Question 14

Gibbs Energy

Answer 14

a spontaneous reaction occurs when the combination of the enthalpy (H) and the entropy (S) result in favorable conditions. the individual values of enthalpy and entropy are not enough to make this call which is where G exists

Question 15

how is G fixed?

Answer 15

G is fixed at temperature and is usually calculated at 298 K

Question 16

formula of G

Answer 16

G = H-TS

Question 17

what is the reaction when S>0 (increase entropy), and H>0 (endothermic, increase enthalpy)?

Answer 17

G < 0 at high temps
G > 0 at low temps
process is spontaneous at high temps

Question 18

what is the reaction when S>0 (increase entropy), and H<0 (exothermic, decrease enthalpy)?

Answer 18

G < 0 at any temp

process is spontaneous at any temperature

Question 19

what is the reaction when S<0 (decrease entropy), and H<0 (exothermic, decrease enthalpy)?

Answer 19

G < 0 at low temps
G > 0 at high temps
process is spontaneous at low temps

Question 20

what is the reaction when S<0 (decrease entropy), and H>0 (endothermic, increase enthalpy)?

Answer 20

G > 0 at any temp

process is nonspontaneous at any temperature

Question 21

formula for the temperature in which a reaction is spontaneous

Answer 21

T = H/S

Question 22

what happens if Q/K < 1?

Answer 22

then ln Q/K < 0, reaction proceeds to the right (G<0)

Question 23

what happens if Q/K > 1?

Answer 23

then ln Q/K > 0, reaction proceeds to the left (G>0)

Question 24

what happens if Q/K = 1?

Answer 24

then ln Q/K = 0, the reaction is at equilbrium (G=0)

Question 25

formula for change in G

Answer 25

G = -RT ln K