Module 13

Question 1

Hess’s Law

Answer 1

Enthalpy is a state function and is therefore independent of path.

Question 2

State function

Answer 2

any quantity that depends solely on the final destination, not on the way you get to that destination

Question 3

for enthalpy, the amount of energy contained in a substance is

Answer 3

independent of how it is made

Question 4

enthalpy of formation (ΔHf)

Answer 4

the ΔH of a formation reaction

Question 5

standard conditions

Answer 5

a temp of 25 C and a pressure of 1.00 atm

Question 6

standard enthalpies of formation

Answer 6

the ΔHf for molecules under standard conditions

denoted with an “°”

Question 7

the ΔH° of any chemical reaction is the

Answer 7

sum of the ΔHf° for the products minus the sum of the ΔHf° for the reactants

Question 8

when a reaction is exothermic energy will be thought of a s

Answer 8

a product in the reaction

Question 9

when a reaction is endothermic energy will be thought of as

Answer 9

a reactant in the reaction

Question 10

enthalpy

Answer 10

the energy stored in a substance
stated as the ‘enthalpy of that substance’
symbolized by ‘H’

Question 11

change in enthalpy (ΔH)

Answer 11

the energy change that accompanies a chemical reaction

Question 12

1 calorie =

Answer 12

4.184 Joules

Question 13

ΔH is positive for – reactions and negative for – reactions

Answer 13

endothermic

exothermic

Question 14

whether a reaction is exothermic or endothermic, energy is both– and– during the course of the reaction. the difference is —

Answer 14

absorbed
released
how much

Question 15

bond energy

Answer 15

the strength of a chemical bond

Question 16

ΔH=

Answer 16

energy required to bread bonds/ energy released when bonds form

Question 17

the standard enthalpy of formation of an element in its elemental form is

Answer 17

zero

Question 18

energy diagram

Answer 18

a ‘picture’ of the energy associated with a chemical reaction

Question 19

reaction coordinate

Answer 19

tells us how close the reaction is to completion

plotted on the horizontal/ x axis of the graph

Question 20

intermediate state/ activated complex

Answer 20

occurs at the top of the hump, which represents the midpoint of the reaction

Question 21

activation energy

Answer 21

the energy necessary to start a chemical reaction

Question 22

entropy

Answer 22

a measure of the disorder that exists in any system

denoted by an ‘S’

Question 23

2nd law of thermodynamics

Answer 23

the entropy of the universe must always either increase or remain the same. It can never decrease

Question 24

which state has the least amount of entropy associated with it? How about the middle amount? What about the highest amount?

Answer 24

solid
liquid
gaseous

Question 25

the entropy of a system increases with – temp

Answer 25

increasing

Question 26

the entropy of a system increases os the matter it contains–

Answer 26

increases

Question 27

ΔS universe ≥

Answer 27

0

Question 28

all substances, even elements have

Answer 28

an absolute entropy

Question 29

what does the Gibbs Free equation tell us?

Answer 29

whether or not a reaction is consistent with the second Law of thermodynamics

Question 30

if a reaction is consistent with the second law, we call it

Answer 30

spontaneous

this is because we know that it con proceed

Question 31

if a reaction is ‘not spontaneous’ it means;

Answer 31

The reaction is not consistent with the second law and therefore cannot occur

Question 32

when ΔG

Answer 32

is consistent with the second law

is spontaneous

Question 33

when ΔG > 0 the reaction

Answer 33

is not consistent with the second law
cannot proceed
is not spontaneous