TEST OF PRACTICAL KNOWLEDGE QUESTION All your burette readings (initials and final) as well as the size of your pipette must be recorded but no account of e...
All your burette readings (initials and final) as well as the size of your pipette must be recorded but no account of experimental procedure is required. All calculations must be done in your booklet.
C and D are inorganic salts. Carry out the following exercises on them. Record your observations and identify any gas(es) evolved. State the conclusions you draw from the result of each test.
(a) Put all of C in a test tube and add about 5 cm of distilled water. Shake thoroughly and test the resulting solution with Litmus paper. Divide the solution into three portions.
(i) To the first portion, add NaOH\(_{(aq)}\) in drops, then in excess.
(ii) To the second portion. add NH\(_{3(aq)}\) in drops. then in excess.
(iii) To the third portion. add AgNO\(_{3 (aq)}\) followed by HCl\(_{(aq)}\)
(b)(i) Put all of D in a test tube and add about 5 cm\(^3\) of distilled water. Shakę thoroughly and feel the test tube.
(ii) To about 2 cm\(^3\) of the solution, add HCl\(_{(aq)}\)
Qualitative Analysis of C and D
Test
Observation
Inference / conclusion
(a) C + distilled water; shake. Test the solution with litmus paper.
C dissolves to give a blue-green solution. Blue litmus paper turns red.
C is soluble and the solution is acidic.
(a)(i) First portion of C solution + NaOH(aq), dropwise and then in excess.
A blue precipitate is formed. The precipitate is insoluble in excess NaOH(aq).
Cu2+ ions are present. The precipitate is Cu(OH)2.
(a)(ii) Second portion of C solution + NH3(aq), dropwise and then in excess.
A light-blue precipitate is formed. It dissolves in excess NH3(aq) to give a deep-blue solution.
Cu2+ ions are confirmed.
(a)(iii) Third portion of C solution + AgNO3(aq), followed by dilute HCl(aq).
A white precipitate is formed with AgNO3(aq). The precipitate remains insoluble on adding dilute HCl(aq).
Cl− ions are present. The white precipitate is AgCl.
(b)(i) D + distilled water; shake and feel the test tube.
D dissolves to give a colourless solution. The test tube feels cold.
The dissolution is endothermic.
(b)(ii) About 2 cm3 of D solution + dilute HCl(aq).
Effervescence occurs. A colourless, odourless gas is evolved; it turns limewater milky.
The gas is carbon dioxide, CO2. D contains CO32− ions.
Identification: C is copper(II) chloride, containing Cu2+ and Cl− ions. D is a soluble trioxocarbonate(IV), that is, a soluble carbonate.
The reaction responsible for the gas evolution is:
