P1- Required Practicals

Question 1

1) Chemical changes

Answer 1

1. Measure 20 cm3 sulfuric acid into the measuring cylinder and pour into beaker
2. Heat acid gently using a Bunsen burner.
3. Add small amounts of insoluble base in this case copper oxide in excess
4. Filter using filter paper and funnel the solution to remove the excess copper oxide
5. Pour the solution into the evaporating basin
6. Evaporate the solution using a water bath until crystals form
7. Leave the evaporating basin in a cool place for at least 24 hours
8. Gently pat the crystals dry between two pieces of filter paper.

Question 2

2) Neutralisation

Answer 2

1. Use pipette to measure 25cm3 of NaOH into conical flask
2. Place conical flask on white tile
3. Fill burette with sulphuric acid using a funnel
4. Record initial reading of acid in the burette
5. Add 5 drops of indicator (phenolphthalein) to conical flask
6. Slowly open burette tap while swirling conical flask
7. Add acid drop-by-drop near the endpoint (colour change)
8. Close burette when colour changes in phenolphthalein (pink to colourless)
9. Record final reading of acid in burette and calculate the titre (volume of acid used to neutralise the alkali)
10. Repeat until you have concordant results.
11. Present results in a table and calculate mean titre
12. Calculate number of moles of NaOH used in titration
13. Find moles of sulphuric acid by dividing moles of NaOH by 2
14. Use the formula [concentration= moles/volume to work out the concentration of sulphuric acid

Question 3

3) Electrolysis

Answer 3

1. Add about 50cm3 of copper chloride solution to a beaker.
2. Add lid and insert electrodes through the holes
3. Attach crocodile leads to electrodes and connect the rods to the DC terminals of a low voltage power supply.
4. Set to 4V and switch the power supply on
5. Using forceps, hold litmus paper near + electrode
6. After few mins turn power supply off, observe the - electrode
7. Record observations at electrodes
8. Repeat experiment with sodium chloride where there
   should be effervescence at negative electrode

Question 4

4) Temperature changes

Answer 4

1. Measure 25cm3 of HCl into polystyrene cup
2. Place cup inside beaker to make it more stable
3. Measure and record temperature of HCl
4. Measure 5cm3 of NaOH and add to polystyrene cup
5. Quickly put lid on cup and gently stir solution with thermometer through hole of lid
6. When reading on thermometer stops changing record temp
7. Repeat steps 4 and 5 adding further 5 cm3 amounts of NaOH to the cup (min total of 40 cm3 must be added)
8. Repeat steps 1–7 to ensure reliability of results.
9. Calculate mean maximum temperature reached for each of the sodium hydroxide volumes