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A-Level Chemistry > Extra stuff to know > Flashcards

Extra stuff to know Flashcards

1
Q

Infrared radiation bonds/atoms

A

Absorb IR - makes them bend/stretch - heavier atoms vibrate more slowly
Stronger bonds vibrate faster

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2
Q

IR radiation atmosphere

A

Relatively unaffected by atmospheric gases - passes through atmosphere to earth’s surface where most is absorbed and some is re-emitted in the form of longer wavelength radiation ; greenhouse gases absorb THIS radiation and they re-emit as radiation which increases temp of atmosphere leading to global warming

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3
Q

Applications of IR

A

Many pollutants can be identified by their IR fingerprints
Breathalysers - more IR radiation absorbed from ethanol = more ethanol

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4
Q

UV

A

Ozone absorbs UV radiation from Sun’s rays on,y allowing a small amount to reach earth’s surface -

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5
Q

When measuring change in entropy

A

MOLES of gas matter

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6
Q

Reactions for fuel cells

A

Overall is the Enthalpy change that accompanies the formation of 1mol of H2O (l)

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7
Q

Acid fuel cell oxidation

A

H2 -> 2H+ + 2e-

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8
Q

Alkali fuel cell oxidation

A

H2 + 2OH- -> 2H2O + 2e-

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9
Q

Colour of copper iodide

A

White

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10
Q

Example of optical isomerism in transition

A

1-2 di amino ethane with 2 cl2 and Co central metal ion (+1 charge overall)

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11
Q

Cis platin

A

Pt central with 2cl and 2 nh3

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12
Q

Testing for bromine extra test

A

Use CONCENTRATED AMMONIA

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13
Q

Why do you use HNO3 first

A

Get ride of the possible white precipitate and any carbonate ions

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14
Q

Light brown precipitate

A

Mn(oh)2

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15
Q

Which hydrogen halide forms the strongest acid

A

HI - weakest bond Enthalpy thus dissociates to produce H+ ions when dissolves in water

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16
Q

Why are di carboxylic acids more soluble?

A

They contain 2 OH groups

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17
Q

When doing organic synthesis

A

Make sure to always add in HEAT

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18
Q

When asked to explain hydration Enthalpy

A

Always link it to attraction to water molecules

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19
Q

When asked to describe how anything except temperature affects K values (like Kc)

A

Just talk about how denominator and numerator changes to reverse the change and restore Kc

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20
Q

When talking about how Enthalpy change of solution changes

A

RATIO of energy produced to number of moles is the same

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21
Q

Why does Al have smaller ionisation energy than Mg

A

Mg has outer electron in 3s and Al has outer electron in 3p ; 3p is higher

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22
Q

Hexaaquacopper + KI

A

Copper iodide = white precipitate
I2 = brown solution

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23
Q

Cl2

A

Pale green

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24
Q

Bromine

A

Orange browney

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25
Neutralisation
Exothermic
26
Why is water bath used
Easily controlled And alcohol is flammable
27
Mno4 titration
Colourless to pink
28
Mno4- colour
Pink
29
Mn2+ colour
Colourless
30
Mno4- + Mn2+ ions
LOOK AT EQUATION AND HOW COLOUR CHANGES IN TITRATION
31
How to figure out degree of unsaturation via bromine molecules
Add in bromine dropwise - whichever one requires more drops = more unsaturated
32
If NH3 turns into NH4+ or a species forms a positive charge
LIKELY THEY HAVE ACTED AS A BASE - ACCEPTED A H+
33
When talking about H+ and OH- in half cell reactions
Equilibrium position what has reacted/been removed and then talk about E CELL VALUES
34
Enthalpy change (delta H)
Multiply by the number of moles (Stoichometry - number in front of species)
35
Explaining why delta G always positive/negative?
Break it down into what happens to delta H and t delta S
36
If increasing initial amount of a reactant in moles
The equilibrium amount of that reactant increases - shifts to the products and that increases too BUT THE OTHER REACTANT DCEREASES - MORE OF IT HAS REACTED ; KC REMAINS THE SAME
37
When doing nitration of benzene
Concentrated HNO3 and CONCENTRATED H2SO4
38
Any aqueous (no solid) half cell
Include platinum electrode and like iodine aqueous and ions in solution
39
Zn + CuSO4
Blue to colourless - zinc displaces copper
40
When making standard solution
Add in LESS than 250cm^3 of water
41
When describing disproportionation
Use the word element not species
42
Redox reaction copper + iodine
2Cu2+ + 4I- -> 2CuI + I2
43
When explaining kp shifts
The last shift always = le chateliers
44
If you increase pressure of equilibrium
Increases pressure of the side of the equilibrium with the most amount of moles Ratio of kp changes THEN EQUILIBRIUM CHANGES WITH LE CHATELIERS ALWAYS THE FINAL SHIFT IS LE CHATELIERS
45
Mg + water
Magnesium hydroxide + hydrogen
46
Magnesium water
Magnesium + water -> Magnesium hydroxide + hydrogen
47
Pre exponential factor A
Is responsible for increased frequency of collisions + correct orientation
48
Graphite and graphene
3 bonding regions - 1 delocalised electron donated can conduct electricity 120 degrees - hexagonal layers
49
Limitation of average bond Enthalpy
In gaseous state AVERAGE calculated form bonds in different chemical environments
50
Q=mcΔT
Dissipation of heat to surroundings Incomplete combustion Evaporation of methanol ALL LESS EXOTHERMIC Non standard conditions
51
As rate increases
So does k
52
Mno4- to mn2+
Deep purple to colourless - read from top of meniscus
53
Electrons in half cells
If mixed together (the solutions) they will flow uncontrollably and release energy
54
Acid vs alkali fuel cell hydrogen
Continuously supplied with fuel and oxygen No CO2 produced
55
Acid more negative electrode
H2 -> 2H+ + 2e-
56
Alkali more negative electrode
2OH- + H2 -> 2H2O + 2e-
57
Why is a excess of a species used in a rates question?
To keep the equilibrium far to the other side -look at EQUILIBRIUM POSITION
58
When talking about pH ratio
[HA]/[A-]
59
Reaction with double the Stoichometry?
To figure out Kp just square root the Kp of the reaction with double the species
60
At an equivalence point what is present?
Only salt and water
61
End point
Point in a titration where the indicator changes colour
62
What do we want with end point and equivalence point
We want both of them happening at the same time (as close together as possible) - end point should lie somewhere on that straight line (equivalence point is at the centre) - so we can observe sharp colour change
63
What is the colour of an indicator at end point
It’s in between the acid and alkali colours so should be in the middle
64
ph Probe
Remove from storage solution and rinse with distilled water
65
Ph probe storage solution
Buffer solution KCl
66
Phenolphthalein
Colourless in acid to red/purple in alkali
67
Bromothymol blue
Yellow in acid and blue in alkali
68
Methyl orange
Red in acid and yellow in alkali
69
Strong base weak acid
Phenolphthalein
70
Strong acid weak base
Methyl orange
71
Standard hydrogen half cell
Hydrochloric acid 1mol dm^-3 Hydrogen gas at 100kPa Inert platinum electrode
72
Does salt bridge react with solution
NO
73
Non rechargeable cells
Provide energy until all chemicals have reacted
74
Rechargeable cells
Chemicals in the cell provide electrical energy - when recharging the reactions of the cells can be reversed
75
Rechargeable cell example
Lithium ion batteries
76
Drawbacks of lithium batteries
Toxic if ingested and rapid discharge of current can cause fire
77
Disadvantage of fuel cells
Hydrogen is flammable with low bp ; hard and dangerous to store and transport
78
Why might emf of a cell change over time
Concentration of ions change - reactants used up
79
To keep emf constant
Ensure that reactants are supplied continuously
80
[Cr(H2O]6]3+
Violet
81
Mn2+ aqua
Pale pink
82
Lime water + carbon dioxide
Forms calcium carbonate
83
Enthalpy change of solution
Lattice Enthalpy + hydration Enthalpy together - they BOTH have an effect
84
How to improve accuracy of titration
Take repeats Reduce percentage error 3dp mass balance should be used
85
Condensation
Exothermic
86
What do photodegradable polymers break down into
Small particles of plastic that are biodegradable
87
Formation of amines?
NH3 + haloalkane makes salt first Then react salt with NaOH to make the amine
88
TLC positioning
The plate is placed in a beaker of the solvent such that level of solvent is below the line
89
Inert carrier gas example
Helium or neon
90
Stationary phase of GLC
A liquid - solubility of sample in stationary phase is what determines it
91
Why use a minimum amount of hot solvent?
To get a saturated solution - if too much solvent added then solution may be too dilute to form crystals ; more likely to dissolve any impurities if you use a lot of solvent
92
Why to wet filter paper?
Keep it in place for the filtration
93
When reducing nitrobenzene
Form NH3+ initially with Sn and HCl then NEUTRALISE WITH NAOH and this forms NH2
94
Ch3COCl
Can polymerise without a catalyst
95
Whenever describing heterocyclic fission
Both electrons from the COVALENT BOND are transferred
96
Practical techniques organic
Dissolve in a minimum amount of hot solvent Cool Filter Dry
97
Longer chain
MORE SURFACE POINTS OF CONTACT
98
Nucleophilic addition nitriles
NaCN + H2SO4
99
Nucleophilic substitution
KCN (in ethanol)
100
If it accepts a proton in a reaction
It is classed as a BASE
101
With further substitution (radical substitution)
Going to need 2Cl2 Will create 2HCl (this is a di-substituted product)
102
CFCs
Very stable - high bond enthalpies ; only attacked by UV in stratosphere
103
Phenol + bromine
Decolourise and WHITE PPT
104
C=C bond nature
LOCALISED
105
Area under curve for GC
Relative concentration - actual concentration = use a calibration curve
106
Primary/secondary/tertiary amines or amides
LOOK AT CARBON CHAINS ATTACHED TO NITROGEN
107
Why can a given Kc expression be used to calculate Kc
Because units cancel - same number of moles each side?
108
Why is Enthalpy change of solution the same?
Same energy released per mole of H2SO4
109
Why do we use a solution in excess
Concentration of HCOOH remains constant?

A-Level Chemistry (28 decks)

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