Required Practical 8

Question 1

Risk assessments

Answer 1

Safety goggles should be worn throughout.

Acid should be heated gently not boiled.

Question 2

Equipment (14)

Answer 2

Dilute cid.
Metal oxide or carbonate
Spatula.
Glass rod.
100cm3 beaker.
Bunsen burner.
Tripod.
Gauze.
Heatproof mat.
Filter funnel and filter paper.
Clamp stand.
Conical flask.
250cm3 beaker.
Evaporating basin.

Question 3

Method

Answer 3

• Measure dilute acid into the 100cm3 beaker.
• Set up the tripod, gauze and heatproof mat. Heat the acid gently using the Bunsen burner until it is almost boiling. Turn off the Bunsen burner.
• Use the spatula to add small amounts of metal oxide (or carbonate) powder. Stir with glass rod. Continue to add the base if it keeps disappearing when stirred.
• Stop adding the base when some of it remains after stirring. Allow apparatus to cool completely.
• Set up the filter funnel and paper over the conical flask. Use the clamp stand to hold the funnel. Filter the contents of the beaker from step 3.
• When filtration is complete, pour the contents of the conical flask into the evaporating basin. Evaporate this gently using a water bath (250cm3 beaker with boiling water) on the tripod and gauze. Stop heating once crystals start to form.
• Leave the crystallising solution in a cool place for at least 24 hours.
• Remove the crystals from the concentrated solution with a spatula. Gently pat the crystals dry between two pieces of filter paper. These are pure dry crystals of salt.