entropy

Question 1

define entropy

Answer 1

the measure of dispersal of energy in a system
- ways that energy can be shared between particles

Question 2

what symbol is given to entropy?

Answer 2

S

Question 3

describe the 2 factors that increase entropy

Answer 3

• more disorder = gases have higher entropy than solids
• more particles on products side

Question 4

what does feasible mean?

Answer 4

spontaneously reactive
- WILL REACT

Question 5

explain why a reaction going from a solid to liquid occurs spontaneously even when a process is endothermic

Answer 5

• change in entropy is greater overall than enthalpy
• change in entropy will be positive
• temp x entropy change will be more positive than enthalpy change
• gibbs free energy will be negative

Question 6

how is entropy change calculated?

Answer 6

entropy of products - entropy of reactants

Question 7

what are the units for entropy?

Answer 7

JK-1mol-1

Question 8

what are the standard conditions for entropy?

Answer 8

100kPa, 298K, 1 mole of substance

Question 9

what is the gibbs free energy equation?

Answer 9

gibbs free energy change = enthalpy change - (temp x entropy)

Question 10

what are the units for enthalpy change?

Answer 10

Jmol-1

Question 11

what are the units for free energy?

Answer 11

Jmol-1

Question 12

when will a reaction be feasible in terms of G?

Answer 12

when it is negative or 0

Question 13

how is enthalpy change calculated?

Answer 13

q = mcT
q / moles

Question 14

will a reaction be feasible if enthalpy is negative and entropy is positive ?

Answer 14

yes at any temperature
- G is always negative

Question 15

will a reaction be feasible if enthalpy is positive and entropy is negative ?

Answer 15

no at any temperature
- G is always positive

Question 16

will a reaction be feasible if enthalpy is negative and entropy is negative ?

Answer 16

yes at low temperature
- G is always negative at low temp

Question 17

will a reaction be feasible if enthalpy is positive and entropy is positive ?

Answer 17

yes at higher temperature
- G is negative at higher temp

Question 18

what type of reaction would never be feasible no matter the temperature?

Answer 18

endothermic reactions with a negative entropy

Question 19

what type of reaction would always be feasible no matter the temperature?

Answer 19

exothermic reactions with a positive entropy

Question 20

what 3 factors does feasibility depend on?

Answer 20

• entropy change
• temperature in the system
• enthalpy change of the system

Question 21

what are the limitations of predictions made by delta G about feasibility in terms of kinetics?

Answer 21

• just because a reaction is feasible does not mean that it will occur at an observable rate
• does not take into account the kinetics of the reaction
• Some reactions are feasible since ∆G is negative, but kinetically not feasible since it just occurs too slowly