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Chemistry Module 5 and 6 > Enthalpy and entropy > Flashcards

Enthalpy and entropy Flashcards

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1
Q

Define entropy

A
  • A measure of the dispersal of energy which is greater when the system is more disordered
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2
Q

What is the symbol of entropy?

A

ΔS

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3
Q

Is a solid or gas more disordered?

A

Gas

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4
Q

What is the unit of standard entropy?

A

J K-1mol-1

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5
Q

How does temperature affect entropy?

A
  • The greater the temperature particles have the more energy and they move more
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6
Q

When a solid ionic lattice is dissolved in a solution what happens to the entropy?

A

Entropy increases due to the ions being more disordered

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7
Q

What’s the equation used for entropy change?

A

S products - S reactants

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8
Q

What is Gibbs free energy equation?

A

ΔG = ΔH - TΔS

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9
Q

What is Gibbs free energy equation?

A

ΔG = ΔH - TΔS

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10
Q

What needs to happen for a reaction to be feasible?

A

ΔG < 0

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11
Q

What are the limitations of the predictions of feasibility made by using ΔG?

A
  • Reaction may have high Ea
  • Rate of reaction may be very slow
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12
Q

Define lattice enthalpy

A

Formation of 1 mole of ionic lattice from gaseous ions under standard conditions

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13
Q

What does a more exothermic lattice enthalpy mean?

A

More exothermic = more stronger ionic bonds

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14
Q

Why is it not possible to measure lattice enthalpy directly?

A

It is not possible to form 1 mole of an ionic lattice from its gaseous ions

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15
Q

Define enthalpy change of solution

A

Enthalpy change that takes place when 1 mole of a solute is completely dissolved in water under standard conditions

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16
Q

Define enthalpy change of hydration

A

The enthalpy change when dissolving 1 mole of gaseous ions in water

17
Q

What factors affect size of lattice enthalpy?

A
  • Ionic size (as ionic size increases lattice enthalpy becomes less negative)
  • Ionic charge (as ionic charge increases lattice energy becomes more negative)
18
Q

Which ions have more negative lattice enthalpy?

A

Smaller ions

19
Q

Describe hydration

A
  • When an ionic lattice is broken the ions become part of the solution
  • Positive ions are attracted to the slightly negative oxygen and negative ions are attracted to the slightly positive hydrogen

Chemistry Module 5 and 6 (5 decks)

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