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Chemistry Module 5 > Entropy/Free Energy > Flashcards

Entropy/Free Energy Flashcards

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1
Q

What is entropy?

A

A measure of the dispersal of energy in a system

The greater the entropy, the more disordered.

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2
Q

What is the sign for entropy?

A

S

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3
Q

Why do all substances possess some disorder?

A

Particles are in constant motion

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4
Q

What factors increase entropy?

A

Molecules have heavier atoms
Molecules have more atoms
Energy is shared between more molecules
Temperature is higher

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5
Q

What can entropy explain?

A

Diffusion of gases/heat
Melting
Dissolving
Energy is being dispersed/entropy is increasing

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6
Q

What has more entropy, liquid or gas?

A

Gas

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7
Q

Definition of standard entropy change

A

The entropy change that accompanies a reaction in the molar quantities expressed in a chemical equation under standard conditions, with all reactants/products in their standard states.

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8
Q

What are the units for entropy?

A

JK⁻¹mol⁻¹

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9
Q

How do you work out standard entropy change?

A

Entropy of products - entropy of reactants

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10
Q

What 3 things effect the feasibility of a reaction?

A

Temperature (T), Entropy change (ΔS), Enthalpy change (ΔH)

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11
Q

What is the sign for free energy change?

A

ΔG

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12
Q

How do you work out ΔG?

A

ΔG=ΔH-TΔS

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13
Q

What is ΔG measure in?

A

KJmol⁻¹

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14
Q

When can a reaction spontaneously occur?

A

When ΔG is less than 0

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15
Q

Will a reaction occur if ΔH= -ve and ΔS= +ve?

A

Yes

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16
Q

Will a reaction occur if ΔH= -ve and ΔS= -ve?

A

Maybe (if ΔH is bigger)

17
Q

Will a reaction occur if ΔH= +ve and ΔS= +ve?

A

Maybe (if ΔS is bigger)

18
Q

Will a reaction occur if ΔH= +ve and ΔS= -ve?

A

Never (ΔG is always +ve)

19
Q

What is T measured in when calculating ΔG?

A

Kelvin (ᴼC+273)

20
Q

How do we determine the temperature that a reaction needs to be to happen spontaneously?

A

ΔG is 0

ΔH/ΔS=T

21
Q

What must you do before using ΔH and ΔS in an equation?

A

Convert ΔH to Jmol⁻¹

22
Q

Why may a reaction that is feasible still not happen?

A

The activation energy may be too high

Chemistry Module 5 (8 decks)

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