TEST OF PRACTICAL KNOWLEDGE QUESTION Credit will... | WAEC SSCE - Chemistry - 2015

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TEST OF PRACTICAL KNOWLEDGE QUESTION

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 inorganic salts. E is a solution of an organic compound. Carry out the following exercises on C, D and E. Record your observations and identify any gas(es) evolved. State the conclusion you draw from the result of each test.

(a) To all of C, add about 2 cm\(^3\) of distilled water in a boiling tube. Shake to dissolve and test the solution with litmus paper.

(b)i) Test E with litmus paper.

(ii) Add all of E to the solution obtained in (a).

(c)(i) Add about 5 cm\(^3\) of distilled water to D in a test tube and shake thoroughly. Divide the resulting solution into two portions.

(ii) To the first portion, add few drops of BaCl\(_{2(aq)}\) followed by excess dil. HCl.

(iii) To the second portion, add HNO\(_{3(aq)}\) in drops and then in excess.

Answer

Test	Observation	Inference / conclusion
(a) Dissolve all of C in about 2 cm³ of distilled water and test with litmus paper.	C dissolves. Red litmus paper turns blue.	The solution of C is alkaline.
(b)(i) Test E with litmus paper.	Blue litmus paper turns red.	E is acidic.
(b)(ii) Add all of E to the solution of C.	Effervescence occurs. A colourless, odourless gas is evolved and turns limewater milky.	The gas is carbon dioxide, CO₂. C contains carbonate or hydrogencarbonate ions, while E is an acid.
(c)(i) Dissolve D in about 5 cm³ of distilled water and divide the solution into two portions.	D dissolves to give a colourless solution.	D is a soluble salt.
(c)(ii) To the first portion add BaCl₂(aq), followed by excess dilute HCl.	A white precipitate forms with BaCl₂(aq). The precipitate remains insoluble in excess dilute HCl.	Sulphate ions, SO₄²⁻, are present. The white precipitate is BaSO₄.
(c)(iii) To the second portion add NH₃(aq) dropwise and then in excess.	A white gelatinous precipitate forms on adding NH₃(aq) in drops. The precipitate dissolves in excess NH₃(aq) to give a colourless solution.	Zn²⁺ ions are present.

Test	Observation	Inference / conclusion
(a) Dissolve all of C in about 2 cm³ of distilled water and test with litmus paper.	C dissolves. Red litmus paper turns blue.	The solution of C is alkaline.
(b)(i) Test E with litmus paper.	Blue litmus paper turns red.	E is acidic.
(b)(ii) Add all of E to the solution of C.	Effervescence occurs. A colourless, odourless gas is evolved and turns limewater milky.	The gas is carbon dioxide, CO₂. C contains carbonate or hydrogencarbonate ions, while E is an acid.
(c)(i) Dissolve D in about 5 cm³ of distilled water and divide the solution into two portions.	D dissolves to give a colourless solution.	D is a soluble salt.
(c)(ii) To the first portion add BaCl₂(aq), followed by excess dilute HCl.	A white precipitate forms with BaCl₂(aq). The precipitate remains insoluble in excess dilute HCl.	Sulphate ions, SO₄²⁻, are present. The white precipitate is BaSO₄.
(c)(iii) To the second portion add NH₃(aq) dropwise and then in excess.	A white gelatinous precipitate forms on adding NH₃(aq) in drops. The precipitate dissolves in excess NH₃(aq) to give a colourless solution.	Zn²⁺ ions are present.

Acids, Bases And Salts (Ghana Only)

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

Tests, Observations and Inferences

Tests, Observations and Inferences

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

Tests, Observations and Inferences

Tests, Observations and Inferences

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