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A-LEVEL CHEMISTRY > B5 Energetics II > Flashcards

B5 Energetics II Flashcards

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1
Q

Define Lattice Enthalpy

A

Enthalpy change that occurs with the formation of 1 mole of an ionic lattice from gaseous ions

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2
Q

What is atomisation

A

Formation of 1mol of gaseous atoms from their elements

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3
Q

Atomisation equation for iodine

A
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4
Q

What is electron affinity

A

Formation of 1mol of gaseous anions from atomised elements and electrons

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5
Q

First electron affinity of chlorine equation

A
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6
Q

When must data be multiplied by 2 in a Born-Haber Cycle

A

When the product has a molar mass of two

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7
Q

When calculating lattice enthalpy from a Born-Haber Cycle, how should the equation be structured

A

With enthalpy of formation of the left-hand side of the equation, and the route on the right

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8
Q

Going clockwise round a Born-Haber cycle, what is the order of the processes

A
  • Atomisations
  • Ionisations
  • Electron Affinities
  • Lattice Enthalpy
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9
Q

What must be remebered with electrons in Born-Haber Cycles

A

The electrons produced by ionisation energies, are used in the affinities

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10
Q

Define Enthalpy Change of Solution

A

Dissolving of one mole of a solute in water

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11
Q

Define Enthalpy Change of Hydration

A

Dissolving one mole of gaseous ions in water, to form aqueous ions

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12
Q

Draw a solution enthalpy cycle, with general terms

A
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13
Q

Draw a solution enthalpy cycle, for sodium chloride

A
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14
Q

What is the affect on deltaT, and the enthalpy change of solution, when the volume of water in an experiment is doubled

A
  • deltaT will half, as the same ammount of energy is transferred to double the volume of water
  • Enthalpy of solution stays the same as the ratio of energy releases: moles, is the same, and so the same energy is released per mole
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15
Q

What is the affect on deltaT, and the enthalpy change of solution, when the mass of the solid is doubled

A
  • deltaT will double, as double the ammount of energy is being transferred to the same volume of water
  • Enthalpy of solution stays the same, as the ratio of energy released: moles, is the same, and so the same ammount of energy is released per mole
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16
Q

How does a greater ionic radius affect the attraction to ions

A

Weaker attraction to ions

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17
Q

How does a smaller ionic radius affect the attraction to ions

A

Stronger attraction to ions

18
Q

How does a greater ionic charge affect the attraction to ions

A

Stronger attraction to ions

19
Q

How does a smaller ionic charge affect the attraction to ions

A

Weaker attraction to ions

20
Q

Explaination of comparing two lattice enthalpies with different ionic radii

A
  • Lattice enthalpy of X is more exothermic than Y
  • As ion X is smaller, so has a smaller ionic radius
  • Therefore attraction to Z- ions are stronger
  • So more energy is needed to break ionic bonds between ions
21
Q

Explaination of comparing two lattice enthalpies with different ionic charge

A
  • Lattice enthalpy of X is more exothermic than Y
  • As X has a 2+ charge, compared to Y which has a 1+ charge
  • X has a greater ionic charge
  • Therefore attraction is stronger to Z- ions
  • So more energy is needed to break ionic bonds between ions
22
Q

Define entropy

A

The term used to describe the dispersal of energy (disorder) within the chemicals making up the chemical system

23
Q

Describe and explain how entropy changes from (s) to (l) [or (l) to (g)]

A
  • Entropy increases
  • As disorder increases
  • As liquid particles have more disorder than solid particles
24
Q

Describe and explain how entropy changes from (l) to (s) [or (g) to (l)]

A
  • Entropy decreases
  • As disorder decreases
  • As solid particles have less disorder than liquid particles
25
Q

Describe and explain how entropy changes when there are more moles of gas a products

A
  • Entropy increases
  • As disorder increases
  • As more more gaseous molecules are produced
26
Q

Describe and explain what happens to entropy when there are less moles of gas in the products

A
  • Entropy decreases
  • As disorder decreases
  • As less gaseous molecules are produced
27
Q

Equation to calculate deltaS

A
28
Q

Unit for entropy

A

Joules (J)

29
Q

Units for deltaS

A

J K(-1) mol (-1)

30
Q

Gibb’s Free Energy Equation

A
31
Q

What is crucial to do when calculating Gibb’s Free Energy

A

Always divide deltaS by 1000, so that it is in kJ

32
Q

What must be done when calculating Gibb’s free energy with the units

A

Divide deltaS by 1000 so it is in kJ

33
Q

Why must deltaS be divided by 1000 when using it in Gibb’s Free Energy equation

A

As deltaG is in kJ, and deltaS is in J

34
Q

Units for deltaG

A

kJ mol(-1)

35
Q

When is a reaction feasible

A

When deltaG is equal to/below zero

36
Q

When does the feasibility of a reaction change

A

When deltaG = 0

36
Q

Describe and explain how increasing temperature affects feasibility

A
  • Feasibility increases, as temperature increases
  • As -TdeltaS becomes more negative than deltaH
  • So deltaG decreases
37
Q

Explain how Gibb’s Free Energy is related graphically

A
38
Q

Draw a graph and annotate where:
* Point where feasibility changes
* deltaH
* What the gradient represents

A
39
Q

What is the gradient when Gibb’s Free Energy is graphical

A

- deltaS

A-LEVEL CHEMISTRY (11 decks)

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