unit 3 thermodynamics

Question 1

spontaneous

Answer 1

proceeds without assistance, temp and pressure affect the spontaneity

Question 2

enthalpy

Answer 2

heat absorbed by a system during constant pressure

Question 3

entropy and 5 things that affect it

Answer 3

measure of randomness in a system. volume and temp affect entropy, along with # independently moving molecules, molar mass, and # of atoms in formula

Question 4

1st law of thermodynamics

Answer 4

energy is neither created nor destroyed

Question 5

2nd law of therm

Answer 5

entropy of the universe increases in any process

Question 6

what are the types of molecule motion?

Answer 6

transitional, vibrational, rational

Question 7

how do you calculate spontaneity

Answer 7

when delta G is negative it is spontaneous, when G is positive it will never never never happen ever like at all.

Question 8

endothermic

Answer 8

heat lost from surroundings

Question 9

exothermic

Answer 9

heat gained in surroundings

Question 10

what is a system?

Answer 10

products and reactants

Question 11

what are surroundings?

Answer 11

literally everything else other than prod + react

Question 12

how to see exothermic in a graph

Answer 12

getting more stable, downwards arrow, heat released, less energy = more stable

Question 13

how to see endothermic in a graph?

Answer 13

getting less stable, heat absorbed, upwards arrow, less energy = more stable

Question 14

how to tell type of reaction from H?

Answer 14

• is exothermic, + is endothermic

Question 15

hess’ law

Answer 15

if a reaction is done in steps, delta H = sum of enthalpy from smaller reactions bc H is a state function, the journey doesn’t matter only the destination

Question 16

most important part of a therm question

Answer 16

checking the equation is equal and balances

Question 17

what are average bond enthalpie?

Answer 17

need energy to break bonds. endothermic, the average amount of energy required to break a mol. most accurate when it involves breaking only a few bonds.

Question 18

how to use bond enthalpy to estimate delta H

Answer 18

make chemical equation, draw lewis structure, count the bonds broken in the products (+) and the bonds formed in the reactants (-), add them together

Question 19

how to tell something is combustion

Answer 19

it has o2 as a product

Question 20

lattice enthalpy

Answer 20

H needed to break something into its components.

Question 21

what does it mean when a reaction gives out heat,

Answer 21

it is exothermic, the bonds made are greater than the bonds broken

Question 22

what is Gibbs free energy?

Answer 22

the amount of energy available to do useful work

Question 23

how to calculate heat

Answer 23

q= MC[delta]T

Question 24

how to calculate entropy

Answer 24

delta S= delta S final - delta S initial

Question 25

what is the Gibbs free energy equation?

Answer 25

delta G= delta H- T delta S

Question 26

what is the heat capacity for water?

Answer 26

4.186

Question 27

what is the calculation for enthalpy?

Answer 27

-Q/mol

Question 28

when H - and S +

Answer 28

spontaneous at all temps

Question 29

when H + and S -

Answer 29

non spontaneous ever

Question 30

when H - and S -

Answer 30

spontaneous at only low temps

Question 31

when H + and S +

Answer 31

spontaneous at only high temps

Question 32

when is S -

Answer 32

when disorder goes down, endothermic reaction, energy is used .