Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

N Chemistry A Level > Topic 13 Energetics II > Flashcards

Topic 13 Energetics II Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Chemistry flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

Why is the first electron affinity exothermic?

A

New force of attraction (FOA) between e- and nucleus made

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the first electron affinity equation

A

X (g) + e- -> X- (g)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why is second (and third and onwards) electron affinity endothermic?

A

Because adding e- and negative ions have repulsion
So energy needs to be put in to overcome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the definition of electron affinity

A

Enthalpy change when one mole of electrons are added to one mole of atoms in the gaseous state to form one mole of anions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the definition of standard enthalpy of atomisation

A

Enthalpy change when one mole of gaseous atoms are formed from the element in its constituent state under standard conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the enthalpy of atomisation? + general equation

A

Exothermic
X (s) -> X(g)
enthalpy change when 1 mol of an element in its standard state is atomised to produce 1 mol of gaseous atoms.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the lattice enthalpy of formation?

A

Enthalpy change When one mole of a solid compound is formed from its gaseous ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the standard enthalpy of formation?

A

Enthalpy change when one mole of a substance is formed from its constituent elements in standard conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why are theoretical and actual lattice energies different sometimes?

A

Bcs the theory assumes the ions are perfectly spherical but they may not be in reality

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the enthalpy of solution?

A

enthalpy change when 1 mole of solid ionic compound is dissolved in water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

write the equation of enthalpy of solution of NaCl

A

NaCl (s) + aq -> Na+ (aq) + Cl- (aq)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Suggest why calcium oxide is insoluble in water.

A

Because the lattice is so strong, lots of energy is needed to overcome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why is the second I.E. of calcium more endothermic than its first I.E.?

A

Decreased ionic radius
So e-s are pulled closer to the nucleus so more energy is needed to overcome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how do sizes of ions affectlattice enthalpies?

A
  • cations: the higher charge density/smaller = more perfectly spherical and ionic
  • anions: the bigger/lower charge den, the more covalent
  • evaluate impact to efoa and magnitude
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are the cation anion combination for the perfect sphere shape lattice? (theoretically)

A

large, low charge den cation
small high charge den anion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are the cation anion combination for the perfect covalent lattice? (theoretically)

A

small, high charge den cation
large, low charge den anion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

explain the interactions between water molecules and fluoride ions when the fluoride ions become hydrated. (2 marks)

A
  • water is polar (δ+) so attracted to F- ions
  • Efoa between them (stronger than H bonds)
18
Q

suggest why the hydration of chloride ion is an exothermic process. (2 marks)

A
  • water is polar, got δ+ to form efoa with Cl-
19
Q

By describing the nature of the attractive forces involved, explain why the value for the enthalpy of hydration for the chloride ion is more negative than that for the bromide ion. (3 marks)

A
  • chloride is a smaller ion
  • so higher charge density
  • so stronger efoa
20
Q

Explain why there is a difference between the hydration enthalpies of the magnesium and sodium ions. (2 marks)

A

Mg2+ charge = smaller and higher charge density than Na+ with 1+ charge
so attracts polar water molecules more strongly

21
Q

What is the definition of enthalpy of hydration?

A

The enthalpy change when 1 mole of a gaseous ion is completely dissolved in water into aqueous ions under standard conditions

22
Q

A reaction is exothermic and has a negative entropy change. This reaction is feasible when it is above or below a certain temperature? Why?

A

Below
As heat is released and has less disorder, le chetelier favours endothermic reaction.
ASK B TO CLARIFY

23
Q

Write the equation of the process when potassium nitrate dissolves in water. (1)

A

KNO3 (s) -> K+ (aq) + NO3- (aq)

24
Q

What is the requirement for a reaction to be feasible?

A

Total entropy must be positive / increase

25
Q

Explain why evaporation of water is spontaneous even though the change is endothermic.
Refer to change in arrangement of water molecules and entropy change.

A

Gases are more disordered than liquids
System increase in enthalpy
Magnitude of change in system > in surrounding

26
Q

When talking about entropy change, mention…

A

Disorder
Ways of arrangement of molecules

27
Q

Why is there a bigger jump in entropy change from liquids to gas than solids to liquids?

A

Difference of disorder is larger between liquids to gas than solids to liquid

28
Q

Explain why the equilibrium yield is unchanged if a catalyst is used in a reaction
CH4 (g) + H2O(g) -> CO(g) + 3H2 (g)

A

Catalysts only lower activation energy
Both forward and backwards reactions are equally increasing

29
Q

∆Stotal =

A

∆Surr + ∆Syst

30
Q

∆Syst =
Or
∆H

A

Products - reactants

31
Q

∆Surr =

A

-∆H / T

32
Q

T=
(Tipping temperature)

A

-∆H / ∆Syst

33
Q

∆G =

A

∆H - Tx∆S
S from System

34
Q

When is a reaction feasible in terms of Gibbs value?

A

If
∆G </= 0 , feasible
∆G > 0 , not feasible

35
Q

How to determine if reaction is feasible (temperature range) in terms of T and ∆Surr?

A

When endothermic, it is feasible when temp > T
When exothermic, it is feasible when temp < T
According to le chetelier, also think of the X graph in booklet

36
Q

If reaction is not feasible (ΔStot is negative) , we say that the reactants are…

A

Thermodynamically stable,
They will not react

37
Q

If the reaction is feasible (ΔStot is positive), we say that the reactants are…

A

Thermodynamically unstable
They will react

38
Q

If a reaction should take place but it doesnt, it is due to…

A

Either
- slow kinetics (activation energy)
- non standard conditions

39
Q

If a non feasible reaction takes place, it is likely that…

A

It is not under standard conditions

40
Q

ΔSyst=

A

Products - reactants

41
Q

Why can’t we just double the enthalpy for C-C to get C=C? (2 marks)

A
  • C=C is weaker than 2x C-C
  • C=C consists of a sigma and pi bond, not two sigmas
42
Q

Name two properties of ions that affect their enthalpy of hydration. (2 marks)

A

Ionic radius
Ionic charge

N Chemistry A Level (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions