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F335 Flashcards

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
How is an absorption spectrum interpreted?
Wavelength of radiation absorbed - Determines colour Shape of absorption band - Shade of colour seen Width of absorption band - Purity of colour seen
26
What is a triglyceride made of?
Glycerol Three carboxylic acids Ester bonds
27
What is the name of a benzene ring with a chlorine attached?
Chlorobenzene
28
What is the name of a benzene ring with an NO2 attached?
Nitrobenzene
29
What is the name of a benzene ring with a carboxyl group attached?
Benzoic acid
30
What is the name of a benzene ring with an aldehyde group attached?
Benzaldehyde
31
What is the name of a benzene ring with a methanol attached?
Benzyl alcohol
32
What is the name of a benzene ring with an -OH attached?
Phenol
33
What is the name of a benzene ring with an -NH2 attached?
Phenylamine
34
What are the reagents, conditions and products of bromination of benzene?
Reactant: Bromine Catalyst: FeBr3 - Iron(III) bromide Product: Bromobenzene
35
What are the reagents, conditions and products of nitration of benzene?
Reactant: HNO3 Catalyst: Concentrated sulphuric acid Conditions: Below 55C Product: Nitrobenzene
36
What are the reagents, conditions and products of sulfonation of benzene?
Reactant: Sulphuric acid Reflux Product: Benzenesulfonic acid
37
What are the reagents, conditions and products of chlorination of benzene?
Reactants: C-Cl Catalyst: AlCl3 Product: Chlorobenzene
38
What are the reagents and conditions of a Friedel-Crafts reaction?
AlCl3 | Reflux
39
How are azo compounds formed?
Coupling reaction | Between diazonium salt and a coupling agent
40
How are diazonium salts prepared?
NaNO2 reacted with HCl to form Sodium Chloride and HNO2 (Nitrous acid) Phenylamine reacted with nitrous acid to form benzenediazonium ion
41
What colour is the compound formed when a diazonium ion reacts with phenol?
Yellow-orange
42
What colour is the compound formed when a diazonium ion reacts with naphthalen-2-ol?
Red
43
What colour is the compound formed when a diazonium ion reacts with phenylamine?
Yellow
44
What are the two most abundant ions in salt water?
Sodium and chloride
45
What is a lattice enthalpy?
The strength of the ionic attractions in a lattice
46
What is the enthalpy change in forming an ionic lattice?
Exothermic | Negative
47
What causes a more negative lattice enthalpy and why?
Increased ionic charge - Attract more strongly | Decreased ionic radii - Closer together so stronger attractions
48
What does it mean when the ions in a solution are hydrated?
They have water molecules bound to them
49
What is the enthalpy of hydration?
The strength of the attractions between ions and water molecules
50
What does the symbol (aq) mean?
Water when it is acting as a solvent
51
What causes the most exothermic enthalpy's of hydration?
Greatest charge | Smallest radii
52
What is the enthalpy change of solution?
Enthalpy of hydration cation + enthalpy of hydration for anion - lattice enthalpy
53
What is the entropy change when a solute dissolves?
Increase in entropy
54
What are cloud condensation nuclei?
Small particles in the atmosphere that bind water molecules together and so encourage the formation of clouds
55
How do you calculate pH?
-log(Concentration of hydrogen ions)
56
How is concentration of hydrogen ions found for a strong acid?
Since reaction goes to near completion, equal to moles of acid put in
57
What assumptions are made about weak acids?
Concentration of hydrogen = Concentration of A- | Amount of HA at equilibrium = Amount of HA put in
58
What is the equilibrium constant equation for a weak acid?
Ka = Concentration of hydrogen squared / Concentration of HA
59
How is concentration of hydrogen ions found for a weak acid?
Rearranging of the equilibrium constant equation
60
How is strength of an acid shown?
The greater its Ka value is or the smaller its pKa value is, the greater its strength
61
What are the differences between strong and weak acids?
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
What are the three ways to reduce the build-up of carbon dioxide in the atmosphere?
Alternative fuels Use fossil fuels more effectively Capture and store carbon dioxide
63
What are the four suggested methods of capturing and storing carbon dioxide?
Turning it into useful products Growing more trees Storing in deep trenches on the sea floor Injecting the gas onto the sea floor
64
What is a buffer solution?
A solution which can resist changes in pH despite the addition of acid or alkali
65
What are buffer solutions usually made from?
A weak acid and one of its salts OR A weak base and one of its salts
66
What assumptions are made about species present at equilibrium for buffer solutions?
All the A- ions come from the salt | Almost all the HA molecules remain unchanged
67
What can the equilibrium equation for a buffer solution be written as?
Ka = Concentration of hydrogen ions * (Concentration of salt / Concentration of acid)
68
How can fine and coarse tuning of a buffers pH be done?
Coarse tuning - Modifying the value of Ka | Fine tuning - Changing the ratio of concentrations of salt and acid
69
What are the equations for the carbon dioxide equilibria in water?
CO2(g)CO(aq) CO2(aq) + H2O(l) H+(aq) + (HCO3)-(aq) (HCO3)-(aq) H+(aq) + (CO3)2-(aq)
70
What is the overall equation for the carbon dioxide equilibria?
CO2(g) + H2O(l) 2H+(aq) + (CO3)2-(aq)
71
What is specific heat capacity?
A measure of how much energy is required to warm something up
72
What are the three forms of kinetic energy molecules can possess?
Translation Rotation Vibration
73
What is entropy?
A measure of the number of ways of arranging molecules and distributing their quanta of energy
74
What substances have higher entropies?
Ones with heavier atoms and more atoms
75
How is the entropy change for the surroundings calculated?
- Enthalpy change ------------------------------ Temperature in Kelvin
76
How is the total entropy change calculated?
Entropy change for the system + Entropy change for the surroundings
77
What must the entropy change be for reactions to occur?
Positive
78
What are spontaneous changes?
Changes which occur of their own accord as the total entropy change is positive
79
What is the entropy change for a reaction?
Total entropy change for the products - Total entropy change for the reactants
80
What is the entropy change for an equilibrium to occur?
Zero
81
Why does waters density decrease when frozen?
It expands
82
What two areas are focused on when designing a new medicine?
Developing a biological understanding of the condition | Finding a lead compound to use
83
What does n.m.r. look at?
The different chemical environments hydrogen nuclei are in
84
How is splitting determined?
One more peak than the number of adjacent hydrogen nuclei
85
What are the three stages in preparing an organic compound?
Reaction Extraction of product Purification of product
86
What is a target molecule?
The desired compound
87
What is retrosynthetic analysis?
The process of working backwards from the target molecule in order to devise a synthetic route
88
What is a disconnection?
An imagined breaking of a bond to suggest two fragments that could be reacted together to get the target molecule
89
What is a synthon?
An idealised fragment resulting from a disconnection
90
What is a synthetic equivalent?
The actual compounds used that function as synthons
91
How are penicillins normally made?
Adding side-chains to 6-APA

Chemistry (6 decks)

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