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Chemistry A2 > Chapter 22 > Flashcards

Chapter 22 Flashcards

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1
Q

Define Lattice Enthalpy

A

Lattice enthalpy is the enthalpy change when one mole of ionic compound is formed from its gaseous ions under standard conditions.

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2
Q

What is the sign of lattice enthalpy ? Why?

A

Negative, as bond are forming. So its an exothermic reaction.

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3
Q

Why are Born-Haber Cycles used?

A

Used because lattice enthalpy cannot be measure directly.

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4
Q

Is Lattice formation endothermic or exothermic?

A

Endothermic

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5
Q

Is the formation of gaseous atoms endothermic or exothermic?

A

Exothermic

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6
Q

Is the Enthalpy change of formation endothermic or exothermic?

A

Exothermic

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7
Q

Define Enthalpy Change of Atomisation

A

The enthalpy change for the formation of one mole of gaseous atoms of an elements in its standard state under standard conditions.

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8
Q

Is Enthalpy change of atomisation exo or endothermic?

A

Endothermic

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9
Q

Define First ionisation energy

A

The enthalpy change when one electron is removed from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions.

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10
Q

Why is the First ionisation energy always endothermic?

A

Energy is required to overcome the attraction between positive nucleus and negative electron.

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11
Q

Define the first electron affinity

A

The enthalpy change when on electron is added to each atom in one mole of gaseous atoms to form one mole of gaseous 1- ions

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12
Q

Why is the first electron affinity exothermic?

A

Exothermic as electron is being added is attracted to the nucleus.

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13
Q

What is the exception to the first electron affinity rule?

A

When more than one electron is added to an atom, the second on is repelled by the first, so the second electron affinity is likely to be positive.

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14
Q

What happens when a substance dissolves in solution?

A

H20 can overcome the electrostatic attractions between oppositely charged ions and break up the giant ionic lattice structure.

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15
Q

Define enthalpy change of solution

A

The enthalpy change when one mole of solute dissolves in a solvent

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16
Q

Define enthalpy change of hydration

A

The enthalpy change when one mole of gaseous ions dissolve in water to form one mole of aqueous ions

17
Q

What factors effect lattice enthalpy?

A
  1. Size of ion

2. Charge on ion

18
Q

How does the size of the ion effect lattice enthalpy?

A
  1. Ionic radius increases
  2. Attraction between ions decreases
  3. Lattice enthalpy is less negative
  4. Melting point decreases
19
Q

How does the charge on the ion effect lattice enthalpy?

A
  1. Ionic charge increases
  2. Attraction between ions increases
  3. Lattice energy becomes more negative
  4. Melting point increases
20
Q

How does size of ion affect hydration enthalpy?

A
  1. Ionic radius increases
  2. Attraction between ion and water molecules decreases
  3. Hydration energy less negative
21
Q

How does the charge on an ion affect hydration enthalpy?

A
  1. Ionic charge increases
  2. Attraction with eater molecules increases
  3. Hydration energy becomes more negative
22
Q

When can solubility occur?

A

When the energy released from hydrating the ions is equal to or greater than the energy required to break up the lattice.

23
Q

Define entropy

A

A measure of the dispersal of energy in a system

24
Q

What is symbol of entropy?

A

S

25
Q

Between solids, liquids and gases how does entropy change?

A

Solids have the smallest entropy
Liquids have greater entropy
Gases have the highest entropy

26
Q

What happens when a system become more chaotic?

A

Positive entropy change

27
Q

What happens when a system becomes less random?

A

Negative entropy change

28
Q

How does number of moles effect entropy?

A

More moles of result in an increase in entropy

29
Q

Define standard entropy of a substance

A

The entropy of one mole of that substance under standard conditions

30
Q

What is the equation for entropy change?

A

Entropy change = (Sum of entropy of products) - (Sum of entropy of reactants)

31
Q

When is a reaction energetically feasible?

A

If the products have lower overall energy than the reactants

32
Q

What is free energy change?

A

The overall change in energy during a chemical reacion

33
Q

What is the Gibb’s Equation?

A

ΔG = ΔH - TΔS

34
Q

What unit is the temperature in the Gibb’s Equation in?

A

Kelvin

35
Q

How is a reaction feasible? (free energy)

A

Must have a decrease in free energy

36
Q

How is the reaction affected if Δ G = -Ve?

A

Proceeds spontaneously to the right

37
Q

How is the reaction affected if ΔG = Zero?

A

Is at equilibrium

38
Q

How is the reaction affected if ΔG = +Ve?

A

Will not proceed

Chemistry A2 (1 decks)

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