C3 Revision Notes - Sets 1&2 only.pdf
Transcript of C3 Revision Notes - Sets 1&2 only.pdf
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MENDELEEV:
Arranged by atomic mass
Similar properties
Left gaps for elements yet
to be discovered
NEWLANDS:
Built on Daltons Law of
Octaves ( every 8
th
elementhad similar properties)
Arranged by atomic mass
Two elements in same box
Early Periodic Table
PeriodicTable
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Modern Periodic TablePeriodic
Table
Metals/Non-metals
Arranged by proton
number Groupsnumber of
electrons on outer
shell
Periodsnumber ofshells
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Group 1Alkali Metals
PeriodicTable
Group 1 metals1+ ion
Li, Na, Kless dense than water
Reaction with water --> make H2
Alkali metals.metal hydroxide
Universal indicatorpurple Down grouplower mpt/bpt
Reactivity INCREASES down the group Larger atom
Outer electron further away from +ve nucleus
EASIER to lose due to SHIELDING effect of
other electrons
Less electrostatic force
Stored in oil,
as reacts with
oxygen in air
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Group 7Halogens
PeriodicTable
Group 7 non-metals1- ion
Coloured vapours
Diatomic molecules
Down the grouphigher mpt/bpt
Forms ionic compounds with Grp1
Reactivity DECREASES down the group
Larger atom
Outer shell further away from +venucleus
HARDER to gain an electron due to
SHIELDING effect of other electrons
Less electrostatic force to attract
electron
HALOGEN
DISPLACEMENT
A more reactivehalogen will
displace a less
reactive one from a
compound
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Transition MetalsPeriodic
Table
Compared with Group 1
Higher mpt
Higher density
Stronger/harder
Much less reactive
Used for catalysts
Form coloured compoundsIons with different charges
Similar properties because they fill
an inner 3rdshell ( 3d shell). This
can hold 18 electrons, once 2
electrons fill the 4thenergy level.
Usually have same number of
electrons on outer shell
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Water Cycle
Water
Water
evaporates due
to Suns thermal
energy. Condenses to
form clouds
Precipitation (
rain/snow/sleet)
occurs.
Ionic compounds are soluble, butcovalent ones are not.
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Hard WaterWater
Contains Mg2+ and Ca2+ ions, dissolvedwhen water passes through rocks
+ve
- Ca for
bones/teeth
-ve
- Kettles furrow upless efficient
Soft watereasy lather
Hard waterless lather
SCUM
When hard waterreacts with soap.
SCALEWhen hard water
is heated.
SCALE is basically limescale which is Calcium
Carbonate which is a solid ppt and forms on
metal appliances reducing efficiency.
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Removing Hard WaterWater
Add Sodium CarbonatePrecipitates out the Ca and
Mg ions to form insoluble
carbonates
Use
washing
soda
IonExchange
(water
softener)
Filled with resin.
Contain Sodium/Hydrogen Ions
As the water is passed through
the resin, the Na/H ions are
EXCHANGED with the Ca/Mg
ions.
Needs to be topped up with Na
ions so NaCl is poured in to
replenish.
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Water TreatmentWater
Distillation =
PURE WATER
Made safe to drink by removingsolids and micro-organisms
Carbonreduces Cl levels
Ion exchange resin
Silverdiscourage bacterial
growth on filter
Water sourceFilter solids
Sedimentation of small particles using
Aluminium sulphate
Chlorineused to disinfect
Filter of fine sand
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PeriodicTable
Water
Acids &Alkalis
Energy
Analysis
C3
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Strong/Weak Acids/AlkalisAcids
&Alkalis
TESTING whether strong or weakuse Universal Indicator
STRONG ACIDS fully
dissociate into their ionsHCl H+ + Cl-
WEAK ACIDS partially
dissociate into their ionsCH3COOHH+ + CH3COO-
Same for alkalis, just OH- ions
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TitrationAcids
&Alkalis
Used to determine accurately how much alkali is needed to
react completely with a known volume of acid ( or vice-versa)
Phenolphthalein STRONG
ALKALI and WEAK ACID
Methyl Orange STRONG ACID
and WEAK Alkali
NEUTRALpH7
Known
volume
and conc
Unknown
volume
END POINTAcid-base
reaction is
complete
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Energy from fuelsAcids
&Alkalis
Energy
Calorimeter
Think
HSW!
Bomb
calorimeter
4.2J raises
temp of 1 g
of water by
1 degree
Food high in carbs and fats have
lots of energy!! more than
body needs obesity
A + BCIf 0.1 mole of reactants. Total mass of A and B is
100g.
Temp start is 19.6, temp max is 26.1
Work out diff.6.5
(Dont need to learn this, you would get this)
So for 0.1 moles = 2730J
For 1 mole 2730 x 10 27300J (27.3kJ)
..exothermic reaction ( as temp rise) = -27.3kJ/mol
Energy change = mass x 4.2 x temp change
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Energy changesAcids
&Alkalis
Energy
Reaction = bond breaking ( endo) and bond making ( exo)
EXOTHERMIC
Energy required to break
bonds in less than energy
released when new bonds
are formed
ENDOTHERMIC
Energy required to break
bonds in greater than
energy released when new
bonds are formed
CATALYST.
Lowers activation
energy
H = - ve
H = + ve
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Bond energiesAcids
&Alkalis
Energy
CH4(g)+ 2O2(g) 2H2O(l)+ CO2(g)
Identify the bonds..stick diagrams!
Bond Bond energy
kJ/mol
H-H 436
Cl-Cl 242
H-Cl 431
O-H 464
C-C 347
C-O 335
O=O 498
H = bond breaking + (- bond making)
Add up on the bonds in the reactants.
This is bond energy needed to break the bonds
Add up on the bonds in the products.
This is bond energy needed to make new bonds.
REMEMBER making new bonds is an exothermic
reactionso it is always a ve number
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Positive Ions
metal flame test colour
barium apple greencalcium brick red
potassium lilac
lithium bright red
sodium orange
Acids&
Alkalis
EnergyAnalysis
FLAME TESTS
Add
Sodium
Hydroxide
Cu 2+
Fe 3+
Fe 2+
Add NaOH, gently warm.
Ammonium gas turn red litmus
paper blue
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Negative IonsAcids
&Alkalis
EnergyAnalysis
Carbonatesadd acid
bubblesif they
turn limewater cloudy
Copper CarbonateCopper Oxide
Zinc CarbonateCopper Oxide
Halides Add nitric
acid and silver nitrate
Cl Br I
White Cream Yellow
SULPHATES
( add HCl to removes
any carbonate ions)
Add Barium Chloride
white ppt
NITRATES
Test for ammonia first negative resultAdd ALUMINIUM ( this reduces the
nitrate ion to Ammonium ions)
Test again for ammonia gas positive
result
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Titration Calculations
2NaOH + H2SO4Na2SO4+ 2H2O
Write what you know from the question.
V = 30cm3 Conc = ? V = 20cm3 Conc = 0.5
1. Convert vol into
dm3 by dividing
by 1000.
2. Calculate moles
of substance of
known vol and
conc
Moles = Concentration Volume
3. Look at the
equation for the
ratio. Here, it is 2:1
So we calculate
moles of acid here
and then multiply
this by 2
4. Now rearrange the formula
to allow you to work out the
unknown
If they want you to work
out the g/mol
All you do is multiply the
RFM ( they give you
this!) by the
concentration you
calculated
Analysis
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What is ammonia?
It is made industrially by reacting
nitrogen with hydrogen in the Haber
process. It is a reversible reaction,
so it never goes to completion.
hydrogennitrogen + ammonia
N2(g) 3H2(g) 2NH3(g)+
Ammoniais an important compound
in the manufacture of fertilizer and
other chemicals such as cleaningfluids and floor waxes.
Why is this a problem for companies
making ammonia?
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What is yield?The amount of product made in a reaction is called the
yieldand is usually expressed as a percentage.
ammon
iayield(%)
pressure (atm)
The yield of ammonia produced by the Haber process
depends on the temperatureand pressureof the reaction.
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What is the Haber compromise?
In practice, though, these
conditions are not used. Why?
The highest yield of ammonia
is theoretically produced by
using a low temperature anda high pressure.
A compromise is reached to make an acceptable yield in
a reasonable timeframe while keeping costs down.
Lowering the temperature slows down the rate of reaction.
This means it takes longer for ammonia to be produced.
Increasing the pressure means stronger, more expensive
equipment is needed. This increases the cost of producingthe ammonia.
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The Haber compromiseTo produce a high yield of ammonia, but with a fast rate
of reaction and without the need for overly expensive
equipment, the Haber process is carried out at 450Cand 200 atmospheres.
The most important factor in
deciding what conditions to use istherefore not yield, but total cost.
raw materials
equipment
energy
wages
What costs are involved in
the industrial production of
ammonia?
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Maximizing productivityWhat else can be done to maximise productivity in the
manufacture of ammonia?
An iron catalyst is used to increase the rate of
reaction. It speeds up both the forward and backward
reaction, so the position of equilibrium is not affected.
The ammonia is cooled, liquefied and then removed
as it is produced. This causes the equilibrium to shift to
the right to produce more ammonia.
Unreacted nitrogen and hydrogen are recycled andgiven another chance to react.
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What is dynamic equilibrium?In some reversible reactions, the forward and backward
reactions largely occur in the same conditions and at the
same rate.
These reactions are said to be in dynamicequilibrium
there is no overallchange in the amount of products and
reactants, even though the reactions are ongoing.
Dynamic equilibrium can only take place in a closed system,
otherwise the products would escape.
reactant A
+
productreactant B
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Setting dynamic equilibriumThe position of dynamic
equilibrium is not always at a
half-way point, i.e. when there areequal amounts of products and
reactants. It may be at a position
where there are mainly reactants
with a little product, or vice versa.
The position of equilibrium is influenced by two main factors:
temperature
concentration (or pressure for reactions involving gases)
Adding a catalyst speeds upthe time it takes to reach
equilibrium, but does not change the positionof equilibrium.
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Opposing changeWhenever a change is made to a reversible reaction in
dynamic equilibrium, the equilibrium will shift to try and
oppose the change.
Increasing the temperature shifts the
equilibrium in the direction that takes in heat.
Increasing the concentration of a substance
shifts the equilibrium in the direction that
produces less of that substance.Increasing the pressure shifts the equilibrium
in the direction that produces less gas.
Temperature
Concentration
Pressure
Condition Effect
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Exothermic and endothermic reactionsAll reactions are exothermic(give out heat) in one direction
and endothermic(take in heat) in the other.
If the temperature is increased:
If the temperature is decreased:
equilibrium shifts to decreasethe temperature
equilibrium shifts in the endothermicdirection
equilibrium shifts to increasethe temperature
equilibrium shifts in the exothermicdirection
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Concentration and equilibriumChanging the concentration of a substance affects the
equilibrium of reversible reactions involving solutions.
increasingthe
concentration of
substance A
equilibrium shifts to
decreasethe amount of
substance A
=
decreasingthe
concentration ofsubstance A
equilibrium shifts to
increasethe amount ofsubstance A=
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Pressure and equilibriumChanging the pressure has an effect on the equilibrium of
reversible reactions involving gases.
If the pressure is increased:
equilibrium shifts to decreasethe pressure
equilibrium shifts in the direction of fewest
molecules
If the pressure is decreased:
equilibrium shifts to increasethe pressure
equilibrium shifts in the direction of most
molecules
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Alcohols
What Are Alcohols?
Alcohols are organic chemical compounds which forma homologous series.
They are compounds in which one or more hydrogenatoms in an alkane (saturated hydrocarbon) arereplaced by hydroxyl (OH) groups.
The hydroxyl group (OH) is the part of the moleculethat is responsible for the characteristic reactions andchemical properties of the alcohol. This is otherwiseknown as the 'functional group'
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Ethanol
Ethanol is an alcohol.
Ethanol can be represented in a number ofdifferent forms:
C2H5OH CH3CH2OH
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Facts about Ethanol
Ethanol can:
Dissolve in water to form a neutral solution.
React with sodium to from hydrogen.
Burn in air. Be used as fuels and solvents, and is the main
alcohol in alcoholic drinks.
Ethanol can be oxidised to ethanoic acid (bychemical oxidising agents or microbial action).
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So what does Ethanol look like?
The molecular structure of ethanol looks like
this:
The OH part of Ethanol is
sometimes referred to as
the functional group
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Methanol
Methanol is another alcohol, which as we
know, is also a member of the homologous
series.
Methanol can be represented as a formula:
CH3
OH
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Methanol
The molecular structure of methanol look like
this:
The OH part of methanol is sometimes
referred to as the functional group!
http://localhost/var/www/apps/conversion/tmp/scratch_3//upload.wikimedia.org/wikipedia/commons/f/f1/Methanol_Lewis.svg -
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Facts about Methanol
Methanol can:
Dissolve in water to form a neutral solution.
React with sodium to from hydrogen.
Burn in air.
Be used as fuels and solvents, and is the main
alcohol in alcoholic drinks.
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Carboxylic acid
A carboxylic acid is an organic acid that
contains one or more carboxyl groups. They
usually have higher boiling points than water
and are usually quite weak acids. These longerchain acids tend to be rather soluble in less-
polar solvents such as ethers and alcohols.
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Ethanoic Acid
Ethanoic acid can be found in your kitchen,any ideas? Yes, its vinegar! Ethanoic acid is
one of the simplest carboxylic acids.
The COOH part of ethanoic acid is sometimesreferred to as the functional group
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Facts about Carboxylic acids
Carboxylic acids:
Dissolve in water to produce acidic solutions.
React with carbonates to produce carbon dioxide.
React with alcohols in the presence of an acidcatalyst to produce esters.
Do not ionise completely when dissolved in waterand so are weak acids.
Aqueous solutions of weak acids have a higherpH value than aqueous solutions of stronger acidswith the same concentration.
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Esters
Esters are chemical compounds made by
condensing acids with alcohols. Esters with
low molecular weight are commonly used as
fragrances and found in essential oils andpheromones.
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Making an Ester
Ethyl ethanoate is synthesized in industry mainly via the
classic Fischer esterification reaction of an ethanol (alcohol)
and a ethanoic acid (carboxylic acid). This mixture converts to
the ester in about 65% yield at room temperature:
CH3CH2OH + CH3COOHCH3COOCH2CH3+ H2O
The reaction can be accelerated by acid catalysis and the
equilibrium can be shifted to the right by removal of water.
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What do esters look like?
-Ethyl ethanoate-
Ethyl ethanoate is the organic compound with the
formula CH3COOCH2CH3. This colourless liquid has a
characteristic sweet smell and is used in glues, nail
polish removers, decaffeinating tea and coffee, andcigarettes.
The COO part of ethyl ethanoate is