Chemistry - Required practicals

How to prepare a pure, dry sample of a soluble salt?

Measure 20 cm3 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 excess (until no more reacts thus no more effervescence is produced).

4.Filter using filter paper and funnel the solution to remove the excess.

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.

How to determine the concentration of acid that reacts with an alkali of known concentration?

1. Use the pipette to measure 25cm3 of an alkali into the conical flask.

2. Place the conical flask on a white tile.

3. Fill the burette with an 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. - These are within 0.1cm3 of each other

How to electrolyse aqueous solutions using graphite rods?

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 off and observe the negative electrode.

7. Record observations at the electrodes.

Investigate variables that effect temperature change in chemical reactions?

1. Measure 25cm3 of hydrochloric acid into a polystyrene cup inside a 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