-Flame Test:
Potassium gave the flame colour lilac. Its electron configuration is:
1s2 2s2 2p6 3s2 3p6 4s1; for example, an electron in the s sublevel on the energy level 4, could leap into a sublevel in the energy level 5, and could directly jump back into the 4s level which could give out the certain amount of energy that will enable us to observe the flame colour lilac.
Iron (III) gave the flame colour bright yellow; this could be due to contamination, normally no specific colour is observed when a flame test is done for Iron (III). Its electron configuration is:
1s2 2s2 2p6 3s2 3p6 4s1 3d5; as it is seen, the 4s and 3d orbitals aren’t fully filled. This effects the movement of the electrons when it gains energy and no specific colour is observed.
Nickel (II) gave the flame colour blue green. Normally it does not give a specific flame colour. Its electron configuration is:
1s2 2s2 2p6 3s2 3p6 4s1 3d8; as it is seen, the 4s and 3d orbitals aren’t fully filled. This effects the movement of the electrons when it gains energy and no specific colour is observed.
-Precipitation Tests: The precipitation tests which take place could either be single replacement reactions or double placement reactions. Double replacement reaction is when two ionic reactants break their bonds and associate with the anion or cation which is from other reactant.
In the Sodium Hydroxide test; hydroxides occur within the solution once a few drops of sodium hydroxide is added into the solution. Precipitation indicates that the test was successful.
Nickel (II) Sulphate reacting with Sodium Hydroxide gives a green precipitation and once excess Sodium hydroxide is added the precipitation becomes insoluble:
Iron (III) Chloride gives a foxy brown precipitation with sodium hydroxide and once excess Sodium hydroxide is added the precipitation becomes insoluble:
However, with Potassium Sulphate there is no precipitation that is observed, the solution is colourless.
In the Ammonia test;
Nickel (II) Sulphate formed green precipitation and when excess ammonia was added the precipitation dissolved to give a blue solution:
Iron (III) Chloride formed foxy brown precipitation and when excess ammonia was added the precipitation became insoluble:
Potassium Sulphate gave a colourless solution at first and when excess ammonia was added it formed white precipitation; however, this indicates that the reaction was unsuccessful.
In the Sodium carbonate test;
Nickel (II) Sulphate formed blue precipitation with Sodium carbonate, normally Nickel forms green precipitation:
Iron (III) Chloride formed green precipitation with Sodium carbonate, normally Iron (III) forms brown precipitation:
Potassium formed white precipitation with sodium carbonate.
- Explain how the anion tests work.
In the Barium Chloride test;
When barium chloride was added to Nickel (II) sulphate white precipitation was formed and when hydrochloric acid was added the precipitation became insoluble:
When barium chloride was added to Iron (III) sulphate no precipitation was observed, the solution was colourless and when hydrochloric acid was added there was still no difference, the solution was still colourless; this indicates that the reaction was unsuccessful.
Potassium Sulphate formed white precipitation and when hydrochloric acid was added the precipitation became insoluble:
In the Silver nitrate test;
Iron (III) chloride formed white precipitation when silver nitrate was added:
Both the solutions Nickel (II) Sulphate and Potassium Sulphate formed colourless solutions, this indicates that the reaction was unsuccessful.