2.2 reaction feasibility

Question 1

what is the standard enthalpy of formation

Answer 1

the enthalpy change when one mole of a substance is formed from its elements in their standard states

Question 2

what is the standard state of a substance

Answer 2

the most stable state at a pressure of 1 atmosphere and at a specified temperature, usually taken as 298K

Question 3

how can the standard enthalpy of a reaction be calculated

Answer 3

• from the standard enthalpies of formation of the reactants and products
• products - reactants

Question 4

what is meant by the entropy of a system

Answer 4

a measure of the degree of disorder of the system

Question 5

what is the symbol for entropy

Answer 5

S

Question 6

true or false: the greater the degree of disorder, the lower the entropy

Answer 6

false

Question 7

true or false: the greater the degree of disorder, the greater the entropy

Answer 7

true

Question 8

do solids have high or low disorder

Answer 8

low

Question 9

do gases have high or low disorder

Answer 9

high

Question 10

does entropy increase or decrease as temperature increases

Answer 10

increase

Question 11

is there a rapid or a slow increase in entropy at the melting point of a substance

Answer 11

rapid

Question 12

is the increase in entropy more rapid and larger at the melting point or the boiling point of a substance

Answer 12

boiling point

Question 13

what does the second law of thermodynamics state

Answer 13

the total entropy of a reaction system and its surroundings always increases for a spontaneous process

Question 14

does the heat energy released by a reaction system into the surroundings increase or decrease the entropy of the surroundings

Answer 14

increase

Question 15

does the heat energy absorbed by the reaction system from the surroundings decrease or increase the entropy of the surroundings

Answer 15

decrease

Question 16

what does the third law of thermodynamics state

Answer 16

the entropy of a perfect crystal at 0K is zero

Question 17

what is the standard entropy of a substance

Answer 17

the entropy value for the substance in its standard state

Question 18

how can the change in standard entropy for a reaction system be calculated

Answer 18

from the standard entropies of the reactants and products

Question 19

when is a reaction said to be feasible

Answer 19

when the change in free energy between reactants and products is negaitive, and a reaction occurs

Question 20

what is the change in free energy related to

Answer 20

enthalpy and entropy changes

Question 21

what is a feasible reaction

Answer 21

one that tends toward the products rather than the reactants

Question 22

does a reaction being feasible give an indication on the rate of the reaction

Answer 22

no

Question 23

how can the standard free energy change be calculated

Answer 23

from the standard free energies of formation of the reactants and products

Question 24

how can the feasibility of a reaction under standard conditions be predicted

Answer 24

from the calculated value of the change in standard free energy

Question 25

how can the temperatures at which a reaction may be feasible be estimated

Answer 25

by considering the range of values of T for which the free energy is greater than zero

Question 26

when is any reaction feasible

Answer 26

under non standard conditions, when the free energy value is negative

Question 27

what does free energy equal at equilibirum

Answer 27

0

Question 28

for how long will a reversible reaction proceed spontaneously

Answer 28

until the composition is reached, where free energy = 0.