Required Practicals

Question 1

Method for making salts practical

Answer 1

1. Measure 20 cm3
   sulfuric acid into a measuring cylinder and pour it into beaker.
2. Heat the 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 start to 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

Method for neutralisation

Answer 2

1. Use the pipette to measure 25cm3
   of sodium hydroxide into the conical flask.
2. Place the conical flask on a white tile.
3. Fill the burette with sulphuric acid using a funnel.
4. Record the initial reading of acid in the burette.
   - Make sure to always take readings from the bottom of the meniscus.
5. Add a 5 drops of indicator in this case phenolphthalein to the conical flask.
6. Slowly open the burette tap while swirling the conical flask.
7. Add acid drop-by-drop near the endpoint.
   - At this point the colour will start to change slightly.
8. Close the burette when a colour change occurs in phenolphthalein.
   - The solution turns from pink to colourless.
9. Record the final reading of acid in the burette and calculate the titre. This is the volume
   of acid used to neutralise the alkali.
10. Repeat until you have concordant results.
11. Present results in a table and calculate the mean titre discarding any anomalies when
    calculating the mean.
12. Calculate the number of moles of sodium hydroxide used in the titration.
13. In the balanced equation the ratio between sodium hydroxide and sulphuric acid is 2:1.
    Therefore to find out the moles of sulphuric acid divide the moles of sodium hydroxide
    by 2.
14. Use the formula [concentration= moles/volume (mean titre volume)] to work out the
    concentration of sulphuric acid.

Question 3

method for electrolysis

Answer 3

1. Add about 50cm3
   of copper chloride solution to a beaker.
2. Add the lid and insert electrodes through the holes making sure the electrodes don’t
   touch.
3. Attach crocodile leads to the electrode and connect the rods to the DC terminals of a low
   voltage power supply.
4. Set the power supply to 4V and switch the power supply on.
5. Using the forceps hold the litmus paper near the positive electrode.
6. After a few minutes turn the power supply

Question 5

Method for temperature changes

Answer 5

1. Measure 25cm3
   of hydrochloric acid into a polystyrene cup.
2. Place the cup inside the beaker to make it more stable.
3. Measure and record the temperature of the hydrochloric acid.
4. Measure 5cm3
   of sodium hydroxide and add it to the polystyrene cup.
5. Quickly put a lid on the cup and gently stir the solution with the thermometer through the
   hole of lid.
6. When the reading on the thermometer stops changing and becomes fairly constant,
   record the temperature.
7. Repeat steps 4 and 5 to add further 5 cm3
   amounts of sodium hydroxide to the cup. A
   minimum total of 40 cm3
   needs to be added.
8. Repeat steps 1–7 to ensure reliability of results.
9. Calculate the mean maximum temperature reached for each of the sodium hydroxide
   volumes

Question 6

Method for rate of reactdion

Answer 6

1. Measure 50 cm3
   of 1.0 M hydrochloric acid using one of the measuring cylinders. Pour
   the acid into the 100 cm3
   conical flask.
2. Set up the apparatus as shown in one of the diagrams below.
3. Add a 3 cm strip of magnesium ribbon to the flask and quickly place the bung back into
   the flask. At the same time, start the stopwatch.
4. Record the volume of hydrogen gas given off every 10 seconds. Stop when no more gas
   is given off.
5. Repeat steps 1-4 using 1.5 M hydrochloric acid
6. Plot a graph of ‘volume of gas produced’ (y-axis) against ‘time’ (x-axis) . Draw twocurves, one for each concentration of acid.