Required Practicals (Paper 1)

Question 1

Suggest a method for obtaining pure crystal samples of copper oxide. [6]

Answer 1

• Heat hydrochloric acid [1]
• Add copper oxide and stir till in excess [1]
• Filter to remove excess copper oxide [1]
• Place solution in a basin over a water bath and evaporate half of the liquid [1]
• Pour solution into petri dish [1]
• Leave to crystalize [1]

Question 2

Suggest why a reaction with sodium nitrate would be unsafe to do in the lab.

Answer 2

• It is very explosive/reactive [1]

Question 3

Suggest the reactants needed to form sodium nitrate. [2]

Answer 3

• Sodium [1]

- Nitric acid [1]

Question 4

Name the substance produced when copper oxide reacts with hydrochloric acid. [1]

Answer 4

• Copper chloride [1]

Question 5

Describe an experiment to carry out an electrolysis of copper chloride. [6]

Answer 5

• Place carbon rods in copper chloride solution and attach croc clips [1]
• Attach the croc clips to the power supply [1]
• Turn on the power pack [1]
• Use litmus paper to test for chlorine gas (goes clear when gas is present) [1]
• After 5 minutes, switch off pack [1]
• Check surface of electrodes for copper deposits [1]

Question 6

Name the elements formed during the electrolysis of sodium chloride, and indicate the electrode at which each of them form at. [2]

Answer 6

• Chlorine, anode [1]

- Sodium, cathode [1]

Question 7

Suggest why lead bromide must be molten for an electrolysis to be successful. [2]

Answer 7

• When lead bromide is not molten, it cannot conduct electricity via it’s lattice of electrons. [1]
• When molten, electrons can move and conduct electricity. [1]

Question 8

Suggest a method for performing a titration of sodium hydroxide. [6]

Answer 8

• Pour 25cm3 of sodium hydroxide into a conical flask [1]
• Add indicator to the solution [1]
• Add 50cm3 of HCl with a pipette filler [1]
• Let the HCl flow, dropwise [1]
• Swirl the flask and continue until colour change [1]
• Obtain reading from the burette [1]

Question 9

Explain how the burette is adapted to allow more accurate readings. [2]

Answer 9

• Contains precise measurements [1]

- Allows more accuracy in readings [1]

Question 10

Define precise [1]

Answer 10

• Measurement with little spread around the mean [1]

Question 11

Suggest why the flask is swirled during the titration [2]

Answer 11

• HCl dissolves faster [1]

- so more accurate results [1]

Question 12

Describe an experiment to test variables which affect temperature change. [4]

You should name a suitable acid and hydroxide.

Answer 12

• Measure 50cm3 of HCl in a polystyrene cup [1]
• Measure 5cm3 of sodium hydroxide and record highest temp [1]
• Repeat until 40cm3 of sodium hydroxide has been added [1]
• Empty the cup and refill with HCl to retest again [1]

Question 13

How is thermal energy loss minimised in this experiment? [1]

Answer 13

• Polystyrene as an insulator [1]

Question 14

Predict the resolution of the measuring cylinder the student used to measure 5cm3 of sodium hydroxide. [1]

Answer 14

• Millimetres (accept 0.1cm or mm) [1]

Question 15

(Use table 5 on pg 18 of RQP book as a reference)

Explain how the results of 0.50M and 1.00M are very precise. [2]

Answer 15

• Little spread about the mean [1]

- meaning results are accurate [1]