Chemistry Mock Revision Flashcards
Biopolyesters are…
Biodegradable
Equation for heat energy change
Hey energy change = mass x specific heat capacity x temperature change
Equation for molar enthalpy change
Heat energy change (Q)/moles
What do exothermic reactions do to bonds
MAKE bonds
What do endothermic reactions do to bonds
BREAK bonds
Dicarboxcylic acid + diol —>
Polyester + water
How is ethyl ethanoate produced
Ethanol and Ethanoic acid react in the presence of an acid catalyst
How to calculate Rf value
Distance travelled by component/distance travelled by solvent
How to calculate relative atomic mass
RAM = (isotope abundance (percentage) x isotope mass number) + (isotope abundance x isotope mass number)
How to use electrical conductivity and acid-base character of oxides to classify elements as metals or non-metals
If an element is electrically conductive, and its oxide is a base, then it’s a metal. If an element is not electrically conductive and its oxide is acidic then it’s a non-metal.
Elements in group 7
Fluorine, chlorine, bromine, iodine, astatine
Colours and physical states of group 7 elements
Chlorine - pale green tint, gas
Bromine - red-brown, liquid
Iodine - dark grey, solid
Trends in physical properties of group 7 elements (as you go down the group)
Increasing size
Increasing boiling and melting point
(Decreasing reactivity)
How to use knowledge of trends in group 7 to predict properties of other halogens
Increasing size - halogens further up group will be bigger
Increasing melting and boiling point - “
(Decreasing reactivity - “)
How do displacement reactions of halogens and halides provide evidence for trend in reactivity in group 7
In a reaction between a halogen and halide, if the halide is less reactive that the halogen, it will be displaced by the halogen. If the halide is more reactive nothing will happen.
Explain the trend in reactivity in group 7 in terms of ELECTRONIC CONFIGURATION
Fluorine is most reactive because it has the least shells - stronger force of attraction from nucleus easily attracts one electron to make a full shell. Down the group gets less reactive as they have more shells and a less strong attraction from the nucleus.
Practical: investigate the effect of different solids on catalytic decomposition of hydrogen peroxide solution
- Measure 10cm^3 of hydrogen peroxide into four separate boiling tubes.
- Add 0.5g copper(II) oxide into one of the boiling tubes. Record your observations.
- Weigh a piece of filter paper and then filter the mixture, retain8ng the residue. Rinse boiling tube with distilled water and pour rinsing into filter paper to collect all the remaining solid.
- Allow the filter paper to dry. Reweigh the filter paper and residue.
- Repeat steps 2-4 with a different solid.
(The solids are the catalysts. If the solid is a catalyst it will not be used up so the mass would be the same.)
Ag ion
Ag+
Cu ion
Cu2+
Fe ion (2 options)
Fe2+ or Fe3+
Pb ion
Pb2+
Zn ion
Zn2+
Ammonium
NH4 1+
Carbonate
CO3 2-
Nitrate
NO3 1-
Sulfate
SO4 2-
Definition of ionic bonding
The strong electrostatic attraction between a positive ion and a negative ion
Why do ionic compounds have high melting and boiling points
They have a giant ionic lattice structure with strong electrostatic attar toon between oppositely charged ions therefore a large amount of energy is required to overcome these bonds.
When do ionic compounds conduct electricity
When molten and in an aqueous solution
Definition of covalent bonds
The strong electrostatic force of attraction between a shared pair of electrons and the the nuclei of both bonding atoms
Covalent bonds are between…
Non metal atoms
Why do simple molecular substances have low melting/boiling points
They have a simple molecular structure with weak intermolecular forces of attraction between molecules therefore a small amount of energy is required to overcome the attractions
As molecular mass increases what happens to melting/boiling points
As molecular mass increases the intermolecular forces of attraction become stronger, meaning that more energy is required to overcome them. This means the melting/boiling points increase.
Why do giant covalent substances have high melting/boiling points?
They have a giant covalent lattice structure held together by many strong covalent bonds therefore a large amount of energy is required to overcome these bonds
How does structure of diamond influence physical properties
-diamond cannot conduct electricity because: the C atoms are neutral, the electrons are fixed in covalent bonds, therefore no charged particles can move
-diamond is very hard because it has a rigid tetrahedral arrangement of C atoms, and it is difficult to break the covalent bonds - large amount of energy is required.
How does structure of graphite influence physical properties
-has layers of C atoms with weak forces of attraction between layers
-high melting point because it is giant covalent
-it is very soft because the layers can slide over each other
-each carbon atom forms 3 bonds - but carbon has 4 electrons in its outer shell meaning that one electron per carbon atom is delocalised, meaning it can conduct electricity.
Do covalent compounds usually conduct electricity
NO
How does structure of C60 fullerene influence physical properties
-each molecule is made from 60 C atoms - covalent bonds between C atoms within the molecule. However there are weak intermolecular forces of attraction between molecules.
-low melting point due to the weak intermolecular forces of attraction
-c60 fullerene is soft and slippery because the weak intermolecular forces of attraction mean that the molecules can easily slide over each other
-can NOT conduct electricity because: the molecules are neutral so there are no charged particles that can move (there are delocalised electrons WITHIN the molecules but they can’t move freely only within the molecules)
Definition of metallic bonding
Strong electrostatic force of attraction between a lattice of positive ions and delocalised electrons
How do you calculate reacting masses using chemical equations/experimental data
Work out moles used using moles = mass/mr
Use mole ratio
Then use mass=moles x Mr/Ar
DO THE HIGHLIGHTING THING!! Where you highlight the info you know
How to calculate percentage yield
Percentage yield = actual yield (mass)/theoretical yield (mass) x 100
How to work out the formula for water of crystallisation problems or any other problems where you need to find the formula for a compound
Find out the mass of the compound (e.g. CaSO4)
Foins put the mass of the other compound (could be H2O or something else)
(Make a lil table thing)
Find moles of both from mass
Find the moles ratio (by dividing both by the smallest number)
How to calculate empirical formula from experimental data
Empirical formula is simplest whole number ratio of soles of each element in a compound
Write down the mass of each
Find no. Of moles
Find the ratio - divide by the smallest number
Then write out simplest formula (ie is ration is 1:2, write FeO2)
How to calculate molar formula from experimental data (from the empirical formula)
- Work out empirical formula
- Work out Mr of empirical formula
- Work out Mr of compound you have (usually given in question)
- Divide the total Mr by the Mr of the empirical formula
- Multiply the empirical formula by this number (e.g. FeO2 x 3 = Fe3O6)
Equation using moles, volume and concentration
Moles = volume x concentration (mol/dm^3)
How to convert cm^3 to dm^3
Divide by 1000
Equation using moles and volume (ONLY FOR GASES at same temp and pressure)
Moles = volume in dm^3/24
OR
Moles = volume in cm^3/24000
Practical: determine the formula of a metal oxide by combustion or by reduction
Combustion:
1. Record mass of empty crucible and lid
2. Add magnesium ribbon to it and measure all of that.
3. Heat very strongly ensuring lid is on, but take lid off every minus to let oxygen in.
4. When it is a white solid stop heating. Record mass of the crucible and everything in it.
5. Keep heating for a bit and make sure it’s fully reacted.
6. You can find the formula of the compound made by using moles=mass/Mr and the mass you got from the experiment - use the table thingy.
Reduction:
1. Measure mass of empty reduction tube.
2. Weigh 1g of copper oxide and add it to reduction tube.
3. Turn on supply of methane so the gas tap is half on and flush apparatus for 10 seconds. Ignite excess gas at end of tube.
4. Heat gently at first then heat strongly.
5. At the end record the mass of the tube and the copper (because now it’s just copper not copper oxide).
6. Use moles equation and your results to work out formula using table thingy.
Litmus solution
Acid - red
Alkali - blue
Phenolphthalein
Acid - colourless
Alkali - pink
Methyl orange
Acid - red
Alkali - yellow
How to carry out an acid alkali titration
- Fill the burette with acid and note the starting volume
- Put alkali using pipette to be very precise (25cm^3) in a conical flask with an indicator (I.e. phenolphthalein)
- Slowly add the acid from the burette to the alkali in the conical flask.
- Stop adding the acid as soon as the indicator turns the appropriate colour (for phenolphthalein, colourless)
5 note final volume on burette
The titre is the final reading - initial reading
Solubility rules
All sodium postassions and ammonium compounds are soluble (SAP)
All nitrates are soluble
Chlorides are soluble - exceptions: silver and lead (II)
Sulfates are soluble - exceptions: barium, calcium, lead (II)
Carbonates are insoluble - exceptions: sodium, ammonium, postassiez
Hydroxides are insoluble - exceptions: sodium potassium and calcium, which is slightly soluble
Acid in terms of proton transfer
Acids are proton DONORS
Base in terms of proton transfer
Bases are proton ACCEPTORS
What is a base?
Something that neutralises an acid (ESSENTIALLY AN ALKALI)
What compounds can act as bases
Metal oxides, metal hydroxides, and ammonia
What are alkalis?
Bases that are soluble in water
Which reactions make which salts
Insoluble salts - precipitation
Sodium/potassium/ammonium salts - titration
Any other soluble salts - excess solid method
Prepare a pure dry sample of a soluble salt, starting from an insoluble reactant
Excess solid method (to make copper sulfate)
1. Measure 25cm^3 of sulfuric acid into a boiling tube. Warm in a water bath.
2. Add some copper oxide and stir until it has completely reacted and you can’t see any more
3. Repeat this until some copper oxide remains unreacted in the boiling tube (hence the name excess solid method)
4. Filter the mixture to remove the unreacted copper oxide. Then put filtrate in an evaporating basin
5. Heat with Bunsen burner until Half of it has evaporated.
6. Allow to cool and crystallise
7. Filter crystals from remaining liquid, rinse with distilled water and dry with paper towel.
Prepare a pure dry sample of a soluble salt, starting from an acid and an alkali
Titration
1. Find the amount of acid needed to neutralise the alkali by doing a titration (use indicator).
2. Then repeat with NO indicator and add the titre volume, producing a neutral salt solution.
3. Put the solution in an evaporating basin and heat with Bunsen burner until it has half evaporated.
4. Then leave it to crystallise.
5. Rinse with distilled water and dry with paper towel.
6. There you go!
Prepare a pure dry sample of an insoluble salt starting from two soluble reactants
Precipitation
1. Mix together the two solutions, each containing one of the ions in the desire insoluble salt.
2. Filter the precipitate
3. Wash the precipitate with distilled water
4. Leave to dry
How to make lead sulfate (insoluble)
Add lead (II) nitrate to sodium sulfate
Filter precipitate
Wash with distilled water
Leave to dry
Test for carbon dioxide
Bubble through limewater
It it turns cloudy it is CO2
Test for ammonia
Damp red litmus paper turns blue
Test for chlorine
It bleaches damp litmus paper
Flame test colours - Lithium, sodium, potassium, calcium, copper
Li - red
Na - yellow
K - lilac
Ca - orange-red
Cu- blue green
Test for cation NH4 +
Add sodium hydroxide and warm gently
Test gas that comes off
Damp red litmus paper turns blue
Test for Cu 2+, Fe 2+ and Fe 3+ using sodium hydroxide solution
Dissolve the solids in water
Add 1cm^3 sodium hydroxide solution
Add a bit more if nothing happens
Cu 2+ - blue precipitate
Fe 2+ - green precipitate
Fe 3+ - orange-brown precipitate
Test for Cl-, Br- and I- using acidified silver nitrate solution
Add dilute nitric acid followed by a few drops of silver nitrate solution and gently shake
Cl - white precipitate
Br - cream precipitate
I - yellow precipitate
Test for sulfate
Add dilute hydrochloride acid and then barium chloride solution and gently shake
There will be a white precipitate if sulfate is present
Test for carbonate
Add hydrochloric acid
Put bung in boiling tube attached to delivery tube and bubble gas produced through limewater
If limewater turns cloudy then carbonate is present
Test for presence of water using anhydrous copper sulfate
If water is present it turns from white to blue
Physical test to see if water is pure
Measure the boiling point of the water
Pure water boils at 100 degrees
How to determine the percentage by volume of oxygen in the air using experiments involving the reactions of metals (iron) and non metals (phosphorus) with air
Phosphorus:
-set it alight in a bell jar which is in water and the phosphorus floating in an evaporating basin
-the phosphorus will react with the oxygen
-the water will rise to replace the oxygen being used
-it will rise by about 21% because all the oxygen is used up
Iron:
See later flash card about the core practical
Combustion of magnesium, sulfur and hydrogen in oxygen (observations, chemical equation, oxide - acid or base?)
Magnesium - bright white flame and white solid, 2Mg + O2 —> 2MgO, base
Sulfur - blue flame, S + O2 —> SO2, acid
Hydrogen - pale blue, squeaky pop, 2H2 + O2 —> 2H20, neutral
Describe the formation of carbon dioxide from the thermal decomposition of copper (II) carbonate (its the same for all carbonates)
You heat it with a Bunsen burner and bubble gas produced through limewater
CuCO3 —> CuO + CO2
Solid in test tube would turn from green to black as it goes from copper carbonate to copper oxide
Core practical: determine percentage of oxygen in air using iron
- Put some iron wool in the bottom of a test tube and make sure the iron wool is wet,
- Invert the test tube into a beaker that is half full of water. 3. Measure the height of the air in the testbtube.
- Leave for at least one week. Measure the height of the of the air in the test tube after this.
Essentially the iron reacts and rusts therefore uses up the oxygen, and the water level rises to replace the used oxygen. It will rise about 21%
Why do ionic compounds only conduct when molten or in an aqueous solution
The ionic lattice breaks down and allows the ions to move freely
Describe an experiment to investigate electrolysis of:
1. Molten lead (II) bromide
2. Aqueous solutions of sodium chloride, dilute sulfuric acid and copper sulfate)
Molten lead bromide:
-shove the inert electrodes in it
-at the cathode you’ll have Pb atoms
-at the anode you’ll have Br2 atoms
-2 electrons go from the bromine to the pb so then they’re both atoms
Aqueous sodium chloride:
-at the cathode you’ll have hydrogen because hydrogen is less reactive then sodium
-at the anode you’ll have chlorine because it is a halide
Aqueous sulfuric acid:
-hydrogen at cathode
-oxygen and water (OH) at anode
Copper sulfate:
-copper at cathode
-oxygen and water at anode
Rules for electrolysis - what is produced and why?
Cathode - if the positive ion is less reactive than hydrogen then it is produced, otherwise hydrogen is produced as the less reactive element is produced
Anode - if it is a halide, the halide is produced, if it is not then oxygen and water (OH) is produced
Please stop loudly calling me a careless zebra, instead try learning how copper saves gold
Potassium
Sodium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Tin
Lead
Hydrogen
Copper
Silver
Gold
Oil rig
Oxidation is loss of electrons - this happens at the ANODE
Reduction is gain of electrons - this happens at the CATHODE
How to write half equations
At cathode, there is one product. I.e. 2H+ + 2e- —> H2
At anode, there is two products. I.e. 2Cl- —> Cl2 + 2e-
Half equation for hydroxide at anode
4OH- —> 2H2O + O2 + 4e-
Practical: investigate electrolysis of aqueous solutions
Turn power pack on to 6V
And then basically just do the stuff you know how to do it
How do we extract metals using reactivity series
Anything below aluminium, we use displacement reactions with carbon. Anything above carbon we use electrolysis. For very unreactive metals (eg. Gold) it is possible that no extraction process will be necessary.
Example of reduction by carbon for a metal extraction
3C + 2Fe2O3 —> 4Fe + 3CO2
Properties and uses of aluminium, copper, iron, LC steel, HC steel and stainless steel.
Aluminium - good strength to weight ratio, light, soft, ductile, good conductor of heat and electricity. Kitchen equipment, window frames, overhead electricity cables, drinks cans.
Copper - malleable, ductile, good conductor of heat and electricity, low reactivity, good corrosion resistance. Electrical equipment, spires, doors, roofs, house and car electrical wiring.
Iron - malleable, ductile, lustrous. Used to make steel, used as a catalyst to make ammonia, construction of buildings and bridges.
LC steel - pliable, high malleability, low strength to weight ratio. Automotive parts, bridges, electrical transmission lines, cutting tools.
HC steel - high strength, wear resistant, brittle, durable. Drill bits, springs, saws, high strength wires.
Stainless steel - high resistance to corrosion, tough, wear resistant. Cutlery, sinks, cookware, surgical tools.
What is rust
Hydrated iron (iii) oxide
Definition of homologous series
A group of compounds which have similar chemical properties and the same general formula.
Definition of functional group
A group of atoms responsible for the characteristic reactions of a particular compound (e.g. COOH for carboxcylic acids)
Definition of isomerism
When compounds have the same formula but can have different structures.
What is a substitution reaction
A chemical reaction during which one functional group in a chemical compound is replaced with another functional group
Uses of real goats kill dead fish basically
Refinery gas - domestic heating and cooking
Gasoline - fuel for cars
Kerosene - aircraft fuel
Diesel - fuel for cars
Fuel oil - fuel for ships
Bitumen - road surfacing
What happens in car engines when the temperature gets very high
Nitrogen and oxygen react, forming oxides of nitrogen
How is sulfur dioxide produced from impurities in fossil fuels
Fossil fuels are burnt, and they may have sulfur impurities. This sulfur is oxidised when the fuel is burnt and that produces sulfur dioxide which is released into the air.
Conditions for cracking
Silica or alumina catalyst
600-700 degrees celcius temparature
How to name alkanes
Where the branch branches off from + what the branch actually is + the longest chain in the molecule
I.e. 3-methylpentane
Reaction of alkanes with bromine
Alkane + bromine —> bromoalkane + hydrogen bromide
I.e. CH4 + Br2 —> CH3Br + HBr
MUST BE IN PRESENCE OF UV LIGHT
How to name alkenes
Where the double bond is
I.e. if it’s after the second carbon then it would be but-2-ene
Ethanol microbial oxidation equation
CH3CH2OH + O2 —> CH3COOH + H20
Ethanol + oxygen —> Ethanoic acid + water
In order for this to happen you need:
-air as a source of oxygen
-microbes (catalyst)
Ethanol oxidation using potassium dichromate (VI) and dilute sulfuric acid
CH3CH2OH + 2[O] —> CH3COOH + H2O
Colour change from orange to green
Vinegar smell observed
2 ways ethanol can be manufactured
- Reacting ethene with steam with the presence of a phosphoric acid catalyst, temp 300 degrees celcius and 60-70 atm
C2H4 + H2O —> CH3CH2OH - Fermentation of glucose, temp 30 degrees celcius, using yeast as an enzyme, in absence of oxygen.
C6H12O6 —> 2CH3CH2OH + 2CO2
Reactions of carboxcylic acids with metals and metal carbonates
Metals:
Acid + metal —> salt + hydrogen
2CH3COOH + Mg —> (CH3COO)2Mg + H2
Ethanoic acid + magnesium —> magnesium ethanoate + hydrogen
Metal carbonates:
Acid + metal carbonate —> salt + water + carbon dioxide
2CH3COOH + Na2CO3 —> 2CH3COONa + CO2 + H2O
Ethanoic acid + sodium carbonate —> sodium ethanoate + carbon dioxide + water
How is ethyl ethanoate produced
Ethanol and Ethanoic acid react together
IN THE PRESENCE OF AN ACID CATALYST
Reaction produces ester AND WATER
Structural formula of ethyl ethanoate
CH3CH2COOCH3
How to construct an ester (explained very poorly)
So put the alcohol and the carboxcylic acid next to each other
Take away the H on the end of the alcohol and the OH on the front end of the carboxcylic acid
Then shove what you have left together and put a bond between the O from the alcohol and the C from the carboxcylic acid
And vice verse to get the two products from the ester - shove an H on the alcohol and an OH on the carboxcylic acid
Practical: prepare a sample of an ester such as ethyl ethanoate
- Put a drop of sulfuric acid in a test tube
- Add ten drops of ethanol
- Add 10 drops of Ethanoic acid
- Cover test tube with cling film. Place test tube into 60-80 degrees water bath and leave it to get toasty for 5-10 mins.
- Remove test tube and pour contents into a beaker containing sodium carbonate solution.
- The ester is visible as oily droplets on the surface.
Problems in the disposal of addition polymers
-they are inert therefore do not biodegrade
-they produce toxic gases when burnt
-landfill takes up a lot of space
-recycling is expensive
How to write the repeat unit of a polyester (explained very poorly by a girl who is too excited for Christmas to concentrate on chemistry)
Take away the Hs from the diols and the OHs from the dicarboxcylic acids ON BOTH ENDS JUST GET RID OF THEM ALL AT THIS POINT
Shove brackets round it and put the sticks coming out the ends
Then put +2nH2O on the end cuz that’s important
Practical: investigate temperature changes accompanying various types of reaction
Basically just record the temperature before and after.
For salt dissolving in water literally just dissolve a salt in water and measure temp change.
For neutralisation out same volume of acid and alkali in one pot and measure temp change.
For displacement reaction, add magnesium powder to hydrochloric acid and measure temp change,
For combustion, use those spirit burner things and weight before and after and have water in a pot clamped above and measure the temperature change of that.
