TEST OF PRACTICAL KNOWLEDGE QUESTION Credit will be given for strict adherence to the instructions, for observations precisely recorded and accurate inferen...

TEST OF PRACTICAL KNOWLEDGE QUESTION

Credit will be given for strict adherence to the instructions, for observations precisely recorded and accurate inferences. All tests, observations and inferences must be clearly entered in your als book, in ink, at the time they are made.

C is a mixture of an inorganic and organic compounds. Carry out the following exercises on C: Record your.observations and identity any gases evolved. State the conclusion you draw from the result of each test.

(a) Put all of C into a beaker and add 10 cm\(^3\) of distilled water: Stir the mixture thoroughly and filter. Keep both the filtrate and residue.

(b)(i) Test the filtrate with litmus paper.

(ii) To about 2 cm\(^3\) of the filtrate, add BaCI\(_{2(aq)}\) followed by dilute HCI:

(iii) To another 2 cm\(^3\) portion of the filtrate add NaOH and heat.

(c) Transfer the residue into a boiling tube and add few drops of iodine solution

Tests, observations and inferences for specimen C

Specimen C is separated into a water-soluble portion and a water-insoluble residue as shown below.

Test	Observation	Inference/Conclusion
(a) Add 10 cm3 of distilled water to all of C, stir thoroughly and filter.	C is partially soluble in water. A colourless filtrate and a white residue are obtained.	C is a mixture containing a water-soluble substance and a water-insoluble substance.
(b)(i) Test the filtrate with blue litmus paper.	Blue litmus paper turns red.	The filtrate is acidic.
(b)(ii) Add BaCl2(aq) to about 2 cm3 of the filtrate, followed by dilute HCl.	A white precipitate is formed with BaCl2. The precipitate remains insoluble on adding dilute HCl.	Tetraoxosulphate(VI) ions, (SO42), are present. The white precipitate is barium tetraoxosulphate(VI), BaSO4.
(b)(iii) Add NaOH(aq) to another 2 cm3 portion of the filtrate and heat.	A colourless gas with a pungent or choking smell is evolved. It turns damp red litmus paper blue and forms white fumes with concentrated HCl.	The gas is ammonia, NH3. Ammonium ions, (NH4+), are present.
(c) Add a few drops of iodine solution to the residue.	A blue-black or dark-blue colouration is produced.	Starch is present in the residue.

Final identification: C is a mixture of ammonium tetraoxosulphate(VI),  t r(NH₄)₂SO₄, and starch.

Read lesson note on Acids, Bases And Salts (JAMB)

Read lesson note on Organic Compounds (JAMB)