Paper 3 Practicals Flashcards
(16 cards)
What is the aim of the electrolysis practical?
to successfully set up a microscale electrolysis reaction of a solution and to analyse the products formed
Which chemicals are used in the electrolysis practical?
aqueous copper(II) chloride solution
sodium chloride solution
sulphuric acid
What is the method for the electrolysis practical?
1) set up the electrolysis cell and make sure it is secured to the stand by a clamp and boss
2) fill the cell with sodium chloride solution
3) fill the test tubes with sodium chloride and carefully invert them over the electrodes to collect any gases formed
4) Connect wires and crocodile clips to the electrodes and power supply
5) Turn on the power pack at 12V and turn off once test tubes are filled with gas
6) wash cell thoroughly then repeat with copper chloride then sulphuric acid
How do you test the gases in the electrolysis practical?
wet blue litmus paper for chlorine
lit splint for hydrogen
glowing splint for oxygen
What results could you see in the electrolysis practical?
wet blue litmus paper turning red then bleaching to show presence of chlorine gas
lit splint making squeaky pop to show presence of hydrogen
glowing splint reignited to show presence of oxygen
pink deposit on the cathode (copper)
What are the risks in the electrolysis practical?
hydrogen gas is flammable
chlorine gas is toxic and harmful
sodium chloride is corrosive
sulphuric acid is a strong acid
copper (II) chloride is corrosive
What is the aim of the chromatography practical?
to prepare a sample from the plant leaf and separate the photosynthetic chemicals by thin layer chromatography
What is the method to extract the sample from grass for chromatography?
1) add a small spatula of anhydrous sodium sulphate to the pestle
2) cut up about a spatula of grass into the pestle with a pair of scissors
3) add 3cm^3 of the extraction solvent into the pestle
4) grind the grass with a mortar for 2 mins to break up the grass cells
How do you conduct the chromatography after you have the sample?
1) make a small notch in the silica on your TLC plate to mark the baseline
2) using a capillary tube, dip the tip into the sample and paint a small amount on the plate in level with the notch
3) blow gently on it for 20-30 secs to help the solvent to evaporate
4) repeat steps 2 and 3 till there is a clear green spot on the silica
5) using pipette, add developing solvent to the vial till about 2mm depth - make sure it is under the baseline of your TLC plate
6) place TLC plate in the vial using forceps to make sure the sides of the plate don’t touch the vial then put on the lid
7) remove plate once solvent is about 0.5cm from the top and make a notch to mark the solvent front
8) air dry the plate for 2 mins
Why is anhydrous sodium sulphate used in the chromatography practical?
to absorb the water in the grass so it does not interfere with the chromatography. Chlorophyll also dissolves in water
What is the aim of the distillation practical?
to extract limonene form orange peels by distillation and test for unsaturation
How is the apparatus set up in the distillation practical?
clamp a side arm boiling tube with orange peels and water inside diagonally on a stand.
the test tube should have a cork and thermometer.
place bunsen burner underneath the bottom of the test tube.
place the delivery tube in a test tube which is in a beaker half full of water
What is the method for the distillation practical?
1) cut up orange peels into small pieces (<0.5cm) and fill a side-arm boiling tube 1/3 full.
2) add just enough tap water to the tube to just cover the peel
3) set up the apparatus
4) very gently heat the solution using a half-blue flame for about 5 mins moving the flame up and down the tube in order to minimise boiling of water and burning of orange
5) after the 5 mins, heat the tube more strongly to distil off the water/orange mixture until the collecting test tube is about half full
6) measure and record the temperature of the water/oil vapour
How do you test the distillate for limonene?
1) allow the distillate to stand for 1-2mins until a cloudy later has separated to the top of the test tube - this is called the upper organic layer and has the limonene
2) carefully pipette off the top layer and divide it equally between 2 test tubes
3) add a drop of bromine water to the first tube and a drop of potassium manganate (VII) to the second one
4) both should turn colourless if limonene present as they test for a double bond (unsaturated) which limonENE has
What is the aim of the making salts practical?
to prepare a pure, dry sample of a soluble salt from and insoluble oxide or carbonate
What is the method to make a salt?
1) measure roughly 40cm^3 sulphuric acid into a beaker
2) set up tripod, gauze and heatproof mat then heat the acid gently using a bunsen burner until it is almost boiling
3) use a spatula to add small amounts of copper (II) oxide powder and stir
4) keep adding and stirring till the powder stop dissolving - the solution should be clear blue now
5) filter the solution and put the filtrate into an evaporating basin
6) conduct crystallisation to obtain pure dry crystals of copper (II) sulphate
