Paper 2 Flashcards
What does a titration allow you to do
To find out the amount of acid needed to neutralise an alkali or vice versa
List the equipment needed for a titration
Pipette, pipette filler, burette, conical flask, indicator, acid, alkali (around 25cm3)
Steps of a titration
Add alkali using pipette and pipette filler to concical flask, and add two drops of indicator
Fill burette with acid below eye level
Add acid to alkali using burette, swirling conical flask, go slowly when colour change is about to be reached
Indicator changes colour when all alkali is neutralised (e.g. phenolphthalein is pink in alkali but colourless in acid)
Record volume of acid used to neutralise alkali
How can you make sure you get more reliable results of a titration
Repeat a few times making sure you get the same answer each time
How can you make soluble salts using an acid and an alkali
Perform titration adding alkali to acid, as well as indicator, then do it again without indicator to not contaminate the salt.
Evaporate some of the water and leave to crystalise
Filter off solid and dry it, you’ll be left with a pure, dry salt
How to convert from cm3 to dm3
Divide by 1000
What is metallic bonding
Electrostatic attraction between the nuclei of the positive ions and the electrons
Why can metals conduct electricity
Moving delocalised electrons
Why can metals conduct heat well
Electrons transfer energy quickly
Why are metals malleable
Layers of ions can slide over each other
What do iron copper and aluminium have in common
Density
Lustrous (shiny)
High melting point
High tensile strength (strong and hard to break)
Good conductors
Exclusive properties of iron
Malleable (gates and railings)
Corrodes easily
Used in steel
Exclusive properties of aluminium
Doesnt corrode easily
React quickly with oxygen to form a protective layer of aluminium oxide e.g. drinks can
Less dense (lighter) e.g. planes
Exclusive properties of copper
Good conductor of heat and electricity
Low resistance (efficient at transferring electricity) e.g. electrical components, underfloor heating
Why are alloys harder than pure metals
Because the ions cant slide over each other because the elements have different sized atoms and will distort the layers of pure metal atoms
Uses of low carbon steel
Easily shaped e.g. car bodies
Uses of high carbon steel
Very strong, inflexible, brittle e.g. bridges
Uses of stainless steel
Contains chromium and sometimes nickel, corrosion resistance and hard e.g cutlery
Example of other alloys
Bronze - copper and tin
Brass - copper and zinc
Formula for concentration
Concentration = moles/volume
What is concentration measured in
Moles per dm3
How do you convert from mol/dm3 to g/dm3
mass (g) = moles x RFM
What is Avagadro’s law
One mole of any gas occupies 24dm3
How do you convert the number of moles of any gas at room temp and pressure (RTP)
volume (dm3) = moles of gas x 24
How do you calculate volumes in reaction if you know the masses
Write out balanced equation
Work out RFM of substance you know mass of
Calculate number of moles of substance
Look at ratio
Use vol = mol x 24 to find answer
What is electrolysis
The breaking down of a substance using electricity
What is an electrolyte
A molten or dissolved ionic compound
What happens during electrolysis
An electric current is passed through an electrolyte causing it to decompose.
OILRIG
Oxidation is Loss
Reduction is Gain
Describe the movement of ions during electrolysis
The positive ions (cations) are attracted to the cathode (negative) (reduction as electrons are gained)
The negative (anions) are attracted to the anode (positive) (oxidation as electrons are lost)
Why can molten ionic compounds be electrolysed
The ions can move freely
How would you write a half equation that shows what happens at the cathode
Write down the reactant and the product
Balance equation
Write charges
Balance by adding electrons
Why do covalent compounds not conduct electricity
Because the molecules are neutral and there are no charged particles
Why can’t ionic compounds conduct electricity when solid
Because they are helt together in a lattice form and can’t move
What does inert mean
Unreactive
How would you investigate electrolysis using copper sulphate
Pour copper sulphate into beaker
Put two graphite rods in copper sulphate, attach electrode to negative terminal of DC supply, and other electrode to positive terminal
Fill two test tubes with copper sulphate and position a test tube over each electrode
Turn on power and observe what happens
Test any gas with glowing and lit splint
How would you predict the products of electrolysis in a molten compound
Metals would be attracted to the cathode as they are positivey charged
Non-metals would attracted to the anode as they are negatively charged
What element is formed when sulphate is attracted to the anode
Oxygen
What is an electrochemical cell
A circuit made up of an anode, cathode, electroyte, power source and the wires that connect the two electrons
What happens if there is an halogen present at the anode
Molecules of halogens will be formed, if there arent any present, oxygen will be formed
What happens if hydrogen and metal ions are present
If the metal is more reactive thatn hydrogen, hydrogen gas will be produced, if not, a solid layer of the pure metal will be produced
How do you prepare a sample of pure dry lead sulphate
Add 1 spatula of lead nitrate to test tube, and deionised water
Shake thoroughly so that its dissolved
Do same with 1 spatula of magnesium sulphate
Tip both solutions into small beaker and stir
Filter the precipitate using filter paper and funnel and conical flask
Rinse filter paper with deionised water to make sure all the soluble magnesium nitrate has been washed away
What is solubility
The amount of substance that will dissolve in a given volume of solvent (measured in grams per 100 grams of solvent)
How would you investigate how the solubility of a solid is affected by temperature
Add excess ammonium chloride to water in boiling tube
Stir and place in water bath set to 25 degrees
After 5 mins, check that excess solid has sunk to bottom of tube
Check that its at 25 degrees
Weigh empty evaporating basin
Pour some solution into basin and reweigh
Heat gently using bunsen to evaporate all water
Reweigh
Repeat steps with water at different temps
Solubility formula
Solubility = mass of solid (g) / mass of water removed
Why do covalent compounds not conduct electricity
Covalent substances share pairs of electrons so they dont contain ions and they dont have any charged particles that are free to move and conduct electricity
Things to remember for electrolysis and balanced half equations
- In solutions, there are also H+ ions and OH- from the water
- At the cathode, hydrogen gas is produced if the metal is more reactive than hydrogen e.g. sodium
- If the metal is less reactive than hydrogen e.g. copper, then a solid layer of pure metal will be produced
- At the anode, if halide ions arent present then oxygen will be formed
Explain why alkali metals become more reactive as their atomic number increases
The outer most electron is the furthest from the nucleus as you go down, which means the attraction between the atom and nucleus is weaker, the atoms get bigger as you go down group 1, meaning that the outer electron is more easily lost
