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Chemistry > Module 5 > Flashcards

Module 5 Flashcards

Rate of Reaction, Acid and Bases, Entropy, Enthalpy, Redox, Electrodes, Transition Elements

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1
Q

What is Kc?

A

A quantitative measure of the proportion of reactant in an equilibrium mixture. Large Kc means the equilibrium lies to the right with a high yield of products

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2
Q

What is a homogenous equilibrium?

A

Contains species that all have the same state

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3
Q

What is a heterogenous equilibrium?

A

Contains species that have different states

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4
Q

What is Kp?

A

A equilibrium constant for gaseous equilibriums as it is more convenient to use partial pressures

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5
Q

What is Lattice Enthalpy?

A

The enthalpy change when one mole of an ionic compound is formed from its gaseous ions

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6
Q

Is bond forming endothermic or exothermic?

A

Exothermic

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7
Q

2 factors that affect lattice enthalpy?

A

Ionic size (radius) - smaller ions attract more strongly than larger ions
Ionic charge - ions of greater charge attract more strongly than ions with a smaller charge

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8
Q

What is standard enthalpy change of formation?

A

The enthalpy change when one mole of compound is formed from its elements in their standard states under standard conditions

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9
Q

What is standard enthalpy of atomisation?

A

The enthalpy change when one mole of GASEOUS atoms is formed from its element in its standard state under standard conditions

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10
Q

What is 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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11
Q

What is second ionisation energy

A

The enthalpy change when one electron is removed from each ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions

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12
Q

What is first electron affinity?

A

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

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13
Q

When is second electron affinity

A

The enthalpy change when one electron is added to each ion in one mole of gaseous 1- ions to form one mole of gaseous 2- ions

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14
Q

What is enthalpy change of solution?

A

The enthalpy change that takes place when one mole of a compound (solute) is completely dissolved in water under standard conditions

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15
Q

What two processes take place when an ionic compound dissolves into water?

A

1) The ionic lattice dissociates into its gaseous ions (endothermic)
2) The gaseous ions are hydrated with H2O molecules (exothermic, +ve ions attract slightly negative O, -ve ions attract slightly positive H)

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16
Q

What is standard enthalpy change of hydration?

A

The enthalpy that takes place when one mole of isolated gaseous ions is dissolved into water forming one mole of aqueous ions under standard conditions

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17
Q

What are the standard conditions?

A

101kPa and 298K

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18
Q

273K is what in degrees

A

1

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19
Q

How to work out how many electrons are removed from a mass of an element

A

Take the grams of the element (mass)
divide the mass by the Mr
Times the answer to the above by Avogadro’s constant (in formula book)

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20
Q

Name and bond angle:
2 bond pairs
0 lone pairs

A

Linear, 180

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21
Q

Name and bond angle:
2 bond pairs
1 lone pair

A

Non-linear, 117.5

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22
Q

Name and bond angle:
2 bond pairs
2 lone pairs

A

Non-linear, 104.5

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23
Q

Name and bond angle:
3 bond pairs
0 lone pairs

A

Trigonal Planar, 120

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24
Q

Name and bond angle:
3 bond pairs
1 lone pair

A

Pyramidal, 107

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25
Q

Name and bond angle:
4 bond pairs
0 lone pairs

A

Tetrahedral, 109.5

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26
Q

Name and bond angle:
6 bond pairs
0 lone pairs

A

Octahedral, 90

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27
Q

What is entropy?

A

A measure of the dispersal of energy in a system. The entropy is greater when the system is more disordered. It is always positive. It increases with temperature

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28
Q

What is standard entropy change of reaction?

A

The entropy change that accompanies a reaction in the molar quantities expressed in a chemical equation under standard conditions, all reactant and products being in their standard states

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29
Q

What sign does Gibbs (free energy change) need to be for a reaction to be feasible?

A

Negative

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30
Q

Limitations of predictions made for feasibility

A

-Some reactions have a negative Gibbs but still do not seem to actually take place at the expected temperature
-Feasibility predictions do not take into account the reactions kinetics (rate of reaction)

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31
Q

What is the difference between NH3 and PH3?

A

NH3 has hydrogen bonding which is a stronger intermolecular force than PH3 has

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32
Q

NaSO4 or Na2SO4?

A

Na2SO4

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33
Q

How to work out enthalpy of formation?

A

Products-Reactants

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34
Q

How to work out k from half lives

A

ln2/half life average

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35
Q

If there are two weak acids, which acid becomes the acid in the acid-base pair

A

The acid with the higher Ka value

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36
Q

Ka=

A

Ka=[H+]^2/[HA]

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37
Q

pH of a buffer

A

pKa + log([A-]/[HA])

38
Q

Kw=

A

[H+][OH-] at 298K

39
Q

If you have pH how can you find the [OH-]?

A

14-pH = p0H
10^-pOH = [OH-]

40
Q

Acid is?

A

Acid is a proton donor

41
Q

Base is?

A

Base is a proton acceptor

42
Q

How is a choice of indicator linked to the pH curve?

A

Must change colour within the equivalence point

43
Q

What is a buffer solution?

A

A mixture that minimises pH change on addition of small amounts of an acid or base

44
Q

If the oxidation number is odd, eg (III) or (VII), how many oxygen in the compound and what is the charge

A

Oxygen = oxidation number + 1 / 2
Charge = -1

45
Q

If the oxidation number is even, eg (IV) or (VI), how many oxygen in the compound and what is the charge

A

Oxygen= oxidation number + 2 / 2
Charge = -2

46
Q

Is the oxidising agent in the flask or burette in a redox titration?

A

Burette

47
Q

What is the colour change of oxidation in a manganate (VII) redox titration?

A

pink to colourless

48
Q

What colour does starch indicator turn in the presence of iodine?

A

Blue-black

49
Q

Aqueous iodine is this colour

A

Brown

50
Q

Colour change at end point of titration of iodine and thiosulfate? (starch indicator added)

A

Blue-black to colourless

51
Q

Are the moles of titrated I2 the same as the “liberated”/redox product I2?

A

Yes :)

52
Q

More positive standard electrode potential means

A

greater tendency to gain electrons, and undergo reduction

53
Q

Standard conditions of electrochemical cells

A

298K
1.00moldm-3
1 atm

54
Q

If only aqueous/liquid in the half cell equation, what solid can be the electrode

A

Pt(s) / Platinum solid

55
Q

If there is a gas in the half cell equation what is needed?

A

A gas cylinder is placed over the electrode and low enough to be submerged in the solution. The gas is pumped into the solution this way

56
Q

What is between half cells

A

A salt bridge which completes the electrical circuit and allows the movement of ions between the two half cells

57
Q

Standard hydrogen half cell

A

2H+(aq) + 2e- (reversable arrow) H2(g)
-needs H2(g) (at 1 atm) pumping into H+(aq) (at 1.00moldm-3)
-needs a solid platinum electrode

58
Q

What is the standard electrode potential of a half cell?

A

The electromotive force/voltage of a half cell compared with a standard hydrogen half-cell, measured at 298K with solution concentrations of 1moldm-3 and a gas pressure of 1atm

59
Q

Is the standard cell potential positive or negative?

A

Positive

60
Q

What are primary cells?

A

Non-rechargeable
(provide electrical energy until the chemicals have reacted to such an extent that the voltage falls and the cell is ‘flat’

61
Q

What are secondary cells?

A

Rechargeable
The reaction that provides electrical energy can be reversed during the recharging process

62
Q

What is a fuel cell?

A

A fuel cell uses the energy from the reaction of a fuel with oxygen to create a voltage

63
Q

Alkali Hydrogen-Oxygen fuel cell

A

Reduction: 1/2O2(g) + H2O(l) +2e- -> 2OH-
Oxidation: H2(g) + 2OH-(aq) -> 2H2O(l) + 2e-
Redox: H2(g) + 1/2O2(g) -> H2O(l)

64
Q

Acid Hydrogen-Oxygen fuel cell

A

Reduction: 1/2O2(g) + 2H+(aq) + 2e- -> H20(l)
Oxidation: H2(g) -> 2H+(aq) + 2e-
Redox: H2(g) + 1/2O2(g) -> H2O(l)

65
Q

On a concentration-rate graph, which order corresponds to which line:
-Straight across
-Straight diagonal increasing
-Increasing curve

A

-Straight across is order 0
-Straight diagonal increasing is 1st order
-Increasing curve is 2nd order

66
Q

On a concentration-time graph, which order corresponds to which:
-Straight diagonal decreasing
-Decreasing curve with constant half lives
-Decreasing curve with non constant half lives

A

Straight diagonal decreasing is order 0
Decreasing curve with constant half lives is 1st order
Decreasing curve with non constant half lives is 2nd order

67
Q

What is the rate determining step?

A

The slowest step in a multistep reaction

68
Q

Does a catalyst effect Kc and Kp?

A

No.
It increases the rate of both the forward and reverse reactions by the same amount.

69
Q

Does pressure affect Kp?

A

No

70
Q

If the forward reaction is exothermic and temperature increases, what is the effect on Kp/c

A

The value decreases

71
Q

If the forward reaction is endothermic and temperature increases, what is the effect on Kp/c

A

The value increases

72
Q

Does concentration effect Kc?

A

No

73
Q

What colour is Mn0₄¯?

A

Purple

74
Q

What colour is Cr₂O₇²¯?

A

Orange

75
Q

What colour is Cu²+?

A

Blue

76
Q

What colour is Cu(OH)₂ and what state symbol should it have?

A

Blue(s) Precipitate

77
Q

What colour is Fe²+?

A

Pale Green

78
Q

What colour is Fe(OH)₂ and what state symbol should it have?

A

Green(s) Precipitate

79
Q

What colour is Fe³+?

A

Yellow

80
Q

What colour is Fe(OH)₃ and what state symbol should it have?

A

Rusty-Brown(s) Precipitate

81
Q

What colour is Mn²+?

A

Pale Pink

82
Q

What colour is Mn(OH)₂ and what state symbol should it have?

A

Light-Brown(s) Precipitate

83
Q

What colour is Cr³+?

A

Violet (or Green)

84
Q

What colour is Cr(OH)₃ and what state symbol should it have?

A

Grey-Green(s) Precipitate

85
Q

How is a OH¯ ion produced for a precipitation reaction?

A

Either from aqueous sodium hydroxide, or aqueous ammonia (whereby the ammonia reacts with water to make an equilibrium with OH¯ and NH₄+

86
Q

What do you make from reacting a large excess of NH₃(aq) and Cu²+?

A

Blue precipitate made first will dissolve to a deep blue solution. The complex ion formed contains 4NH₃ ligands and 2H₂O ligands

87
Q

What do you make from reacting Cu²+ and large excess of concentrated HCl(aq)?

A

Blue solution will turn yellow. If HCl is added dropwise until excess a green solution will appear before the yellow. The complex ion formed has 4Cl¯ ligands and a 2¯ charge

88
Q

What happens when a large excess of NaOH(aq) is reacted with Cr³+?

A

The grey-green precipitate will dissolve to make a green solution. The complex ion formed has 6OH¯ ligands and a charge of 3¯

89
Q

What happens when an excess of NH₃(aq) reacts with Cr³+?

A

A purple solution is formed and the grey-green precipitate will dissolve. The complex ion formed had 6NH₃ ligands. 6 molecules of water are a biproduct of this reaction.

90
Q

What three transition element ions don’t change colour when excess NaOH or excess NH₃ is added?

A

Fe²+, Fe³+ and Mn²+

Chemistry (4 decks)

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