Required practicals

Question 1

Describe a method to obtain pure copper sulphate crystals

Answer 1

1. Place some sulfuric acid in a conical flask and warm it in a water bath.
2. Add a spatula of copper oxide powder to the acid and stir with a glass rod.
3. Continue adding copper oxide powder until it is in excess.
4. Filter the mixture to remove the excess copper oxide.
5. Pour the filtrate (the copper sulfate solution) into an evaporating basin.
6. Heat the copper sulfate solution to evaporate half of the water.
7. Pour the solution into a watch glass and leave to allow all of the water to evaporate.

Question 2

Describe a method for electrolysis of copper sulfate solution

Describe how to investigate what happens when aqueous solutions undergo electrolysis.

Answer 2

1. Pour approximately 50cm3 of copper (II) chloride into a beaker
2. Place plastic petri dish with 2 holes in it over the beaker.
3. Insert carbon graphite rod into each hole (electrodes).
4. Attatch crocidile leads to rods then connect rods to terminals of a low-voltage PSU.
5. Then select 4V on PSU and turn it on.
6. The negative electrode (cathode) will get coated with copper. (As copper less reactive than Hydrogen).
7. At the positive electrode (anode) there will bubbles of chlorine gas. (As if halide ion (group 7) is present then it will be discharged.)

Question 3

Describe a method investigating the variables that affect temperature changes in chemical reactions.

Answer 3

1. Measure 30cm3 of dilute HCL into a polystyrene cup.
2. Stand the polystyrene cup inside a beaker (stops the cup from falling over).
3. Use a themometer to measure initial temp of the acid and record in table.
4. Measure 5cm3 of sodium hydroxide solution and transfer this into polystyrene cup.
5. Place plastic lid on top of cup and place thermometer through the hole in the lid. Record highest temperature reached.
6. Repeat but for different volumes of sodium hydroxide.