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Chemistry > Core Practicals > Flashcards

Core Practicals Flashcards

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1
Q

What is the first stage as to work out the composition of ink?

A
  • simple distillation to try and remove the solvent assuming that it has a lower boiling point
  • pour sample into distillation flask
  • gradually heat and the solvent should evaporate and pass into the condenser where it cools and condenses
  • leaves the ink in the flask
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2
Q

What is stage 2 of finding out the composition of ink?

A

Paper chromatography

  • draw a line near the bottom in pencil (insoluble so won’t dissolve with the solvent)
  • put the solvent into the beaker so it is below the line so ink doesn’t dissolve into the water but rather up the page
  • put watch glass on top so it doesn’t evaporate
  • solvent moves up the paper and as the dyes dissolve they will too
  • you will see the different chemicals separate pit
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3
Q

How to measure RF value?

A

-distance moved by solute/distance moved by solvent

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4
Q

How do you do electrolysis of copper sulphate with graphite electrodes?

A
  • copper sulphate contains four different ions (Cu2+,SO42-, H+ and OH-)
  • place copper sulphate solution into the container and place the electrodes in making sure the circuit is complete
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5
Q

With graphite electrodes what is made at the cathode?

A

Copper as it is less reactive than hydrogen
-visible costing on the electrode
Cu2+ + 2e- — Cu

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6
Q

With graphite electrodes what is made at the anode

A

Oxygen and water as there are no halides present
-you should see bubbles and oxygen gas forming
4OH- — O2 + 2H20 + 4e-

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7
Q

How do you do electrolysis with copper electrodes?

A
  • pit copper sulphate solution in the container and put the electrodes in making sure the circuit is complete
  • leave for at least 30 minutes to see a considerable change in mass
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8
Q

What happens to the anode and cathode with copper electrodes?

A
  • mass of anode will decrease. This is because copper is oxidised and looses electrons (Cu—Cu2+ +2e-)
  • mass of cathode will increase as electrons are deposited and offered to nearby copper ions (Cu2+ + 2e- —Cu)
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9
Q

How can you measure the change is mass?

A
  • measure mass of electrodes before
  • dry and measure them again at end of experiment
  • if you increase the current you will increase rate of electrolysis so greater change j. Mass
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10
Q

What are the first 3 stages of titration?

A
  • using a pipette measure a set volume of the alkali into a flask and add a few drops of phenolphthalein indicator to turn it purple
  • fill a Burette with a known concentration and volume of acid
  • use the burette to add the acid to the flask a little at a time, swirling regularly, go slower when you think it’s almost neutralised
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11
Q

What are the last three stages of titration?

A
  • the indicator changes colour when all the alkali has been neutralised (should turn colourless)
  • record the volume of acid used to neutralise it (the titre)
  • repeat to ensure you get similar results and then calculate and mean
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12
Q

What should you do before the actual titration experiment?

A
  • do a rough titration so you have a rough idea of how much is needed to neutralise it.
  • this means you can go slower and more precisely in the real thing when you get closer
  • do it on a white tile so colour change more obvious and do it at eyelevel
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13
Q

What is the method to see SA’s effect on rate?

A

Set up a conical flask, bung and gas syringe

  • place a set volume of hydrochloric acid in a flask and add a set mass of marble chips)
  • measure the volume of gas produced taking readings at regular time intervals
  • repeat with same mass and concentration but finer crushed up chips and then with dissolved powder
  • plot graph (time on X and volume on Y)
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14
Q

What are the first 3 stages to see how reaction changes with temperature?

A
  • measure out a fixed volume of sodium thiosulphate and hydrochloric acid
  • use a water bath to gently heat both solutions to the desired temp before mixing them
  • mix solutions in a conical flask and place over a black cross on a piece of paper that is visible through the solution
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15
Q

What are the last 3 stages to see how reaction changes with temperature?

A
  • watch the black mark disappear through the cloudy yellow silver and time how long it takes till it is no longer visible
  • repeat at different temps with the same controls
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16
Q

Test for anions and cations

A

SEE QUALITATIVE ANALYSIS

17
Q

What are the first 2 stages of burning alcohol to heat up water?

A

-put a set volume of alcohol into a spirit burner and measure the mass of the burner and the fuel using a mass balance
(These can be hazardous so make sure to wear gloves and glasses)
-measure a set volume of distilled water into a copper calorimeter

18
Q

What are the third and fourth stages of burning alcohol to heat up waters?

A
  • insulate the calorimeter using a drought excluded and cover with an insulating life after placing thermometer in (minimises energy loss to surroundings)
  • take initial temp of water and then place burner underneath and light the wick
  • stir the water throughout using thermometer so heat is evenly dispersed and when heat from the thunder has made the temp of the water rise 20° blow the spirit burner out
19
Q

What are the last two stages of burning alcohol to heat up water?

A
  • immediately reweigh the burner and fuel
  • repeat using other alcohol but keep controls constant
  • best fuel is one that is burnt less (smallest change in mass)
20
Q

What are the first two stages of making a soluble salt using an acid and insoluble base?

A
  • react acid that contains one of the ions you want in the salt with an insoluble bad that contains the other ion you need
  • heat the acid in a water bath that speeds up the reaction (do in a fire cupboard to avoid releasing acid fumes)
21
Q

What are the next two stages of making a soluble salt?

A
  • add the base and the two will react to produce a soluble salt and water
  • you will when the base is in excess and all the acid neutralised because the excess solid will just sink to the bottom
  • filter of the excess so solution containers only salt and water
  • heat the solution gently to slowly evaporate off some of these the water, leave to cool and salt to crystallise
  • filter of solid and leave to dry
22
Q

How do you investigate neutralisation?

A
  • measure a set volume of dilute hydrochloric acid into a conical flask
  • measure a fixed mass of calcium oxide using a mass balance and mix
  • wait for the base to react completely and record PH
  • repeat until all the acid has reached (you will see unreacted calcium oxide at the bottom of the flask
  • plot a graph to see how PH changes with mass added

Chemistry (12 decks)

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