5.2.2: Enthalpy and entropy Flashcards

1
Q

Define entropy

A

A measure of the dispersal of energy in a
system which is greater when the system
is more disordered

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2
Q

What is the symbol of entropy?

A

S

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3
Q

Solid or gas, which is more disordered?

A

Gas

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4
Q

What is the unit of standard entropy?

A

J K-1 mol-1

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5
Q

How does temperature affect entropy?

A

The greater temperature particles have more energy and move more. Thus the arrangement of particles become more random. More random arrangement = higher entropy

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6
Q

When a solid ionic lattice is dissolved in solution

what happens to entropy?

A

Entropy increases because the ions are

more disordered

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7
Q

Entropy increases because the ions are

more disordered?

A

Increase in number of gas molecules = increase in entropy

Decrease in number of gas molecules = decrease in entropy

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8
Q

Write the Gibbs’ free energy equation and state what

each symbol means

A
ΔG= ΔH - TΔS
ΔG= gibbs free energy/available energy
ΔH= enthalpy change
T= temperature in kelvin
ΔS= entropy change
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9
Q
Fill in the blanks
ΔH = negative
ΔS = positive
ΔG =?
Feasibility of spontaneous change=?
A

ΔG = always negative

Feasibility of spontaneous change= reaction feasible

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10
Q
Fill in the blanks
ΔH = positive
ΔS = negative
ΔG =?
Feasibility of spontaneous change=?
A

ΔG = always positive

Feasibility of spontaneous change= reaction never feasible

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11
Q
Fill in the blanks
ΔH = positive
ΔS = positive
ΔG =?
Feasibility of spontaneous change=?
A

ΔG = negative at high temperatures

Feasibility of spontaneous change= feasible at high temperatures

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12
Q
Fill in the blanks
ΔH = negative
ΔS = negative
ΔG =?
Feasibility of spontaneous change=?
A

ΔG = Negative at low temperatures

Feasibility of spontaneous change= Reaction feasible at low temperatures

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13
Q

For a reaction to occur spontaneously ΔG must be

positive or negative?

A

Negative

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14
Q

What are the limitations of the predictions of

feasibility made by using ΔG? (2 marks)

A

● Reaction may have high activation energy

● Rate of reaction may be very slow

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