Entropy

Question 1

Differentiate between a spontaneous and non-spontaneous reaction.

Answer 1

Spontaneous: given a necessary amount of activation energy to begin, occurs without continuous outside assistance, complete in open systems.

Non-spont. : continuous supply of energy needed to stimulate the reaction, will stop when energy is no longer applied.

Question 2

What is entropy?

Answer 2

A measure of the randomness or disorder of a system.

Question 3

Standard entropy at SATP is indicated by:

Answer 3

S(degree)

Question 4

What are the units for S at STAP?

Answer 4

J/K

Question 5

A positive Delta S indicates

Answer 5

More random. and therefore more favorable.

Question 6

A less random and less favorable reaction will have a __ Delta S

Answer 6

Negative.

Question 7

What are the two forces allowing a reaction to reach equilibrium?

Answer 7

1. Minimum ENTHALPY (negative Delta H) pushing the forward reaction (exothermic).
2. Maximum ENTROPY (positive Delta S). This makes the reaction more random, and thus, favoured.

Question 8

Why do gases have a higher Delta S than liquids, and liquids a higher Delta S than solids?

Answer 8

Because gases are more random that liquids and liquids more random than solids.

Question 9

Which has a higher Delta S? Aqueous or liquid?

Answer 9

Aqueous

Question 10

What is Gibb’s free energy?

Answer 10

The maximum amount of energy produced by a reaction that can be theoretically harnessed as work.

Question 11

Gibb’s free energy links what two measurements?

Answer 11

change in enthalpy and change in entropy.

Question 12

In addition to DH and DS, what is the third variable in Gibb’s free energy equation?

Answer 12

temperature.

Question 13

In Gibb’s free energy equation, what units must the temperature be in? What conversion must you use?

Answer 13

Kelvin. Degrees C + 273 = degrees Kelvin(K)

Question 14

Gibb’s free energy is indicated by what letter?

Answer 14

Delta G

Question 15

What two equations allow one to calculate Delta G?

Answer 15

DG=DH-T DS and DG=SUMnDG(products) - SUMnDG(reactants)

Question 16

What is the spontaneity and temperature of a reaction with positive DH and positive DS?

Answer 16

Spontaneous with high temperature.

Question 17

A change in G for a reaction indicates:

Answer 17

The reaction is at equilibrium.

Question 18

What is the formula to find the boiling point of a substance at equilibrium? (Hint: Delta G = Delta H - (T x Delta S)

Answer 18

Temperature (or bpt) = Delta H / Delta S

Question 19

What is the spontaneity of a reaction with a POSITIVE Delta H and a NEGATIVE Delta S?

Answer 19

Non-spontaneous

Question 20

What is the spontaneity of a reaction with a NEGATIVE Delta H and POSITIVE Delta S?

Answer 20

Spontaneous.

Question 21

What is the spontaneity and temperature of a reaction with negative DH and negative DS?

Answer 21

Spontaneous with low temperature.