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Chemistry > F335 > Flashcards

F335 Flashcards

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1
Q

What oxidation states can group 5 elements have and why?

A

+ or -3: Three covalent bonds due to three unpaired electrons
+5: Dative covalent bond using lone pair as well

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2
Q

What is the bond between nitrogen atoms in N2?

A

Triple bond

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3
Q

Why does ammonia act as a base?

A

It has a lone pair so can form a dative covalent bond to form the ammonium ion

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4
Q

What is the name and appearance of NO?

A

Nitrogen(II) oxide

Colourless gas

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5
Q

What is the name and appearance of NO2?

A

Nitrogen(IV) oxide

Brown gas

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6
Q

What is the name and appearance of N2O?

A

Dinitrogen(I) oxide

Colourless gas

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7
Q

What is the equation for an equilibrium constant?

A

Concentration of products/Concentration of reactants

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8
Q

What happens to the equilibrium constant if the concentrations are changed?

A

Nothing

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9
Q

What happens to the equilibrium constant if the pressure is changed?

A

Nothing

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10
Q

What happens to the equilibrium constant if the temperature is changed?

A

If exothermic, an increase in temperature results in a decrease in Kc

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11
Q

What happens to the equilibrium constant if a catalyst is used?

A

Nothing

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12
Q

What are the key features of organic farming?

A

Little artificial fertilisers and pesticides used

Emphasis on soil health

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13
Q

How do farmers ensure soil is organically kept fertile and contains enough nutrients?

A

Crop rotations
Growing crops that are ploughed back into the soil
Using composts and manures
Applying certain fertilisers and nutrients

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14
Q

What is the catalyst for the Haber process?

A

Finely divided iron

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15
Q

What is the reaction in the Haber process?

A

Nitrogen gas + Hydrogen -> Ammonia

450 degrees

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16
Q

What is added to soil to increase pH?

A

Lime

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17
Q

Why is DDT banned from being used as a pesticide?

A

Remain in soil

Build up in food chain

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18
Q

What organic measures are used to control pests?

A 
Crop rotation
Physical barriers
Weeding
Limited use of certain pesticides
Growing companion plants close by
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19
Q

What is a chromophore?

A

An extended delocalised electron system

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20
Q

Why do double bonds absorb light in the visible region?

A

Their electrons are more spread out so need less energy to excite

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21
Q

Why do compounds containing transition metals appear coloured?

A

The d orbitals are split into two groups of different energy levels

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22
Q

What is a paint made of?

A

The pigment

The liquid that carries the pigment

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23
Q

What is a reflectance spectrum?

A

White light shone on material, colours missing are the ones absorbed

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24
Q

How does an absorption spectrum work?

A

Shine white light on solution of sample

Measure intensity of absorption for each wavelength

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25
Q

How is an absorption spectrum interpreted?

A

Wavelength of radiation absorbed - Determines colour
Shape of absorption band - Shade of colour seen
Width of absorption band - Purity of colour seen

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26
Q

What is a triglyceride made of?

A

Glycerol
Three carboxylic acids
Ester bonds

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27
Q

What is the name of a benzene ring with a chlorine attached?

A

Chlorobenzene

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28
Q

What is the name of a benzene ring with an NO2 attached?

A

Nitrobenzene

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29
Q

What is the name of a benzene ring with a carboxyl group attached?

A

Benzoic acid

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30
Q

What is the name of a benzene ring with an aldehyde group attached?

A

Benzaldehyde

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31
Q

What is the name of a benzene ring with a methanol attached?

A

Benzyl alcohol

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32
Q

What is the name of a benzene ring with an -OH attached?

A

Phenol

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33
Q

What is the name of a benzene ring with an -NH2 attached?

A

Phenylamine

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34
Q

What are the reagents, conditions and products of bromination of benzene?

A

Reactant: Bromine
Catalyst: FeBr3 - Iron(III) bromide
Product: Bromobenzene

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35
Q

What are the reagents, conditions and products of nitration of benzene?

A

Reactant: HNO3
Catalyst: Concentrated sulphuric acid
Conditions: Below 55C
Product: Nitrobenzene

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36
Q

What are the reagents, conditions and products of sulfonation of benzene?

A

Reactant: Sulphuric acid
Reflux
Product: Benzenesulfonic acid

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37
Q

What are the reagents, conditions and products of chlorination of benzene?

A

Reactants: C-Cl
Catalyst: AlCl3
Product: Chlorobenzene

38
Q

What are the reagents and conditions of a Friedel-Crafts reaction?

A

AlCl3

Reflux

39
Q

How are azo compounds formed?

A

Coupling reaction

Between diazonium salt and a coupling agent

40
Q

How are diazonium salts prepared?

A

NaNO2 reacted with HCl to form Sodium Chloride and HNO2 (Nitrous acid)
Phenylamine reacted with nitrous acid to form benzenediazonium ion

41
Q

What colour is the compound formed when a diazonium ion reacts with phenol?

A

Yellow-orange

42
Q

What colour is the compound formed when a diazonium ion reacts with naphthalen-2-ol?

A

Red

43
Q

What colour is the compound formed when a diazonium ion reacts with phenylamine?

A

Yellow

44
Q

What are the two most abundant ions in salt water?

A

Sodium and chloride

45
Q

What is a lattice enthalpy?

A

The strength of the ionic attractions in a lattice

46
Q

What is the enthalpy change in forming an ionic lattice?

A

Exothermic

Negative

47
Q

What causes a more negative lattice enthalpy and why?

A

Increased ionic charge - Attract more strongly

Decreased ionic radii - Closer together so stronger attractions

48
Q

What does it mean when the ions in a solution are hydrated?

A

They have water molecules bound to them

49
Q

What is the enthalpy of hydration?

A

The strength of the attractions between ions and water molecules

50
Q

What does the symbol (aq) mean?

A

Water when it is acting as a solvent

51
Q

What causes the most exothermic enthalpy’s of hydration?

A

Greatest charge

Smallest radii

52
Q

What is the enthalpy change of solution?

A

Enthalpy of hydration cation + enthalpy of hydration for anion - lattice enthalpy

53
Q

What is the entropy change when a solute dissolves?

A

Increase in entropy

54
Q

What are cloud condensation nuclei?

A

Small particles in the atmosphere that bind water molecules together and so encourage the formation of clouds

55
Q

How do you calculate pH?

A

-log(Concentration of hydrogen ions)

56
Q

How is concentration of hydrogen ions found for a strong acid?

A

Since reaction goes to near completion, equal to moles of acid put in

57
Q

What assumptions are made about weak acids?

A

Concentration of hydrogen = Concentration of A-

Amount of HA at equilibrium = Amount of HA put in

58
Q

What is the equilibrium constant equation for a weak acid?

A

Ka = Concentration of hydrogen squared / Concentration of HA

59
Q

How is concentration of hydrogen ions found for a weak acid?

A

Rearranging of the equilibrium constant equation

60
Q

How is strength of an acid shown?

A

The greater its Ka value is or the smaller its pKa value is, the greater its strength

61
Q

What are the differences between strong and weak acids?

A

Strong acids have lower pH for same concentration
Strong acid has higher electrical conductivity for equivalent concentration
Strong acid has faster reaction rate for equal concentration

62
Q

What are the three ways to reduce the build-up of carbon dioxide in the atmosphere?

A

Alternative fuels
Use fossil fuels more effectively
Capture and store carbon dioxide

63
Q

What are the four suggested methods of capturing and storing carbon dioxide?

A

Turning it into useful products
Growing more trees
Storing in deep trenches on the sea floor
Injecting the gas onto the sea floor

64
Q

What is a buffer solution?

A

A solution which can resist changes in pH despite the addition of acid or alkali

65
Q

What are buffer solutions usually made from?

A

A weak acid and one of its salts
OR
A weak base and one of its salts

66
Q

What assumptions are made about species present at equilibrium for buffer solutions?

A

All the A- ions come from the salt

Almost all the HA molecules remain unchanged

67
Q

What can the equilibrium equation for a buffer solution be written as?

A

Ka = Concentration of hydrogen ions * (Concentration of salt / Concentration of acid)

68
Q

How can fine and coarse tuning of a buffers pH be done?

A

Coarse tuning - Modifying the value of Ka

Fine tuning - Changing the ratio of concentrations of salt and acid

69
Q

What are the equations for the carbon dioxide equilibria in water?

A

CO2(g)CO(aq)
CO2(aq) + H2O(l) H+(aq) + (HCO3)-(aq)
(HCO3)-(aq) H+(aq) + (CO3)2-(aq)

70
Q

What is the overall equation for the carbon dioxide equilibria?

A

CO2(g) + H2O(l) 2H+(aq) + (CO3)2-(aq)

71
Q

What is specific heat capacity?

A

A measure of how much energy is required to warm something up

72
Q

What are the three forms of kinetic energy molecules can possess?

A

Translation
Rotation
Vibration

73
Q

What is entropy?

A

A measure of the number of ways of arranging molecules and distributing their quanta of energy

74
Q

What substances have higher entropies?

A

Ones with heavier atoms and more atoms

75
Q

How is the entropy change for the surroundings calculated?

A
  • ## Enthalpy changeTemperature in Kelvin
76
Q

How is the total entropy change calculated?

A

Entropy change for the system + Entropy change for the surroundings

77
Q

What must the entropy change be for reactions to occur?

A

Positive

78
Q

What are spontaneous changes?

A

Changes which occur of their own accord as the total entropy change is positive

79
Q

What is the entropy change for a reaction?

A

Total entropy change for the products - Total entropy change for the reactants

80
Q

What is the entropy change for an equilibrium to occur?

A

Zero

81
Q

Why does waters density decrease when frozen?

A

It expands

82
Q

What two areas are focused on when designing a new medicine?

A

Developing a biological understanding of the condition

Finding a lead compound to use

83
Q

What does n.m.r. look at?

A

The different chemical environments hydrogen nuclei are in

84
Q

How is splitting determined?

A

One more peak than the number of adjacent hydrogen nuclei

85
Q

What are the three stages in preparing an organic compound?

A

Reaction
Extraction of product
Purification of product

86
Q

What is a target molecule?

A

The desired compound

87
Q

What is retrosynthetic analysis?

A

The process of working backwards from the target molecule in order to devise a synthetic route

88
Q

What is a disconnection?

A

An imagined breaking of a bond to suggest two fragments that could be reacted together to get the target molecule

89
Q

What is a synthon?

A

An idealised fragment resulting from a disconnection

90
Q

What is a synthetic equivalent?

A

The actual compounds used that function as synthons

91
Q

How are penicillins normally made?

A

Adding side-chains to 6-APA

Chemistry (6 decks)

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