Credit will be given for strict adherence to the... | WAEC SSCE - Chemistry - 2012 (Practical)

Question 1 Report

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

C and D are two aqueous solutions. Carry out the following exercises on C and D. Record your observations and identify any gas(es) evolved. State the conclusion you draw from the result of each test.

(a)(i) To about \(2\ \mathrm{cm}^3\) portion of C, add \(\mathrm{NaOH}_{(aq)}\) In drops until in excess. Warm the mixture

(ii) To another \(2\ \mathrm{cm}^3\) portion of C, add \(\mathrm{HCl}_{(aq)}\) followed by \(\mathrm{BaCl}_{2(aq)}\)

(b)(i) (ii) To another \(2\ \mathrm{cm}^3\) portion of D, add add \(\mathrm{NH}_{3(aq)}\) drops and then in excess.

(ii) To about \(2\ \mathrm{cm}^3\) portion of D, add \(\mathrm{AgNO}_{3(aq)}\) followed by \(\mathrm{HNO}_{3(aq)}\)

Answer

Test	Observation	Inference
(a)(i) To C, add NaOH_(aq) dropwise and then in excess. Warm.	No visible reaction or precipitate is formed. On warming, a colourless gas with a pungent, choking smell is evolved. The gas turns damp red litmus paper blue and forms white fumes with hydrogen chloride gas.	The gas is ammonia, NH₃. Ammonium ion, NH₄⁺, is present.
(a)(ii) To a fresh portion of C, add HCl_(aq), followed by BaCl_2(aq).	No visible reaction occurs on adding dilute hydrochloric acid. A white precipitate forms on adding barium chloride solution.	Tetraoxosulphate(VI) ion, SO₄²⁻, is present.
(b)(i) To D, add NH_3(aq) dropwise and then in excess.	A reddish-brown precipitate is formed. The precipitate is insoluble in excess aqueous ammonia.	Iron(III) ion, Fe³⁺, is present.
(b)(ii) To a fresh portion of D, add AgNO_3(aq), followed by HNO_3(aq).	A white precipitate is formed with silver nitrate solution. The precipitate remains insoluble on adding dilute nitric acid.	Chloride ion, Cl⁻, is present.

Test	Observation	Inference
(a)(i) To C, add NaOH_(aq) dropwise and then in excess. Warm.	No visible reaction or precipitate is formed. On warming, a colourless gas with a pungent, choking smell is evolved. The gas turns damp red litmus paper blue and forms white fumes with hydrogen chloride gas.	The gas is ammonia, NH₃. Ammonium ion, NH₄⁺, is present.
(a)(ii) To a fresh portion of C, add HCl_(aq), followed by BaCl_2(aq).	No visible reaction occurs on adding dilute hydrochloric acid. A white precipitate forms on adding barium chloride solution.	Tetraoxosulphate(VI) ion, SO₄²⁻, is present.
(b)(i) To D, add NH_3(aq) dropwise and then in excess.	A reddish-brown precipitate is formed. The precipitate is insoluble in excess aqueous ammonia.	Iron(III) ion, Fe³⁺, is present.
(b)(ii) To a fresh portion of D, add AgNO_3(aq), followed by HNO_3(aq).	A white precipitate is formed with silver nitrate solution. The precipitate remains insoluble on adding dilute nitric acid.	Chloride ion, Cl⁻, is present.

Oxidation And Reduction

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Credit will be given for strict adherence to the instructions, for observations precisely recorded, and for accurate inferences. All tests, observations, an...

TESTS ON SOLUTIONS C AND D

TESTS ON SOLUTIONS C AND D

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Credit will be given for strict adherence to the instructions, for observations precisely recorded, and for accurate inferences. All tests, observations, an...

TESTS ON SOLUTIONS C AND D

TESTS ON SOLUTIONS C AND D

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