Credit will be given for strict adherence to 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 samples of two simple salts. Carry out the following exercises on them. Record your observations and state the conclusion you draw from the result of each test.
(a)(i) Put half of C in a test tube and add about 5cm\(^3\) of distilled water. Test with litmus.
(ii) Put the rest of C in a test tube and add about 5cm\(^3\) of dilute hydrochloric acid. Identify any gases evolved.
(b)(i) Put half of D in a test tube. Add about 5cm\(^3\) of sodium hydroxide solution and warm. Identify any gases evolved.
(ii) Put the rest of D in a test tube and add about 5cm\(^3\) of distilled water. Mix thoroughly. Add about 2cm\(^3\) of barium chloride solution, followed by dilute hydrochloric acid in excess.
Explanation
| Test | Observation | Inference |
| (a)(i) C + water + litmus | Soluble in water to give a colourless solution which turns red litmus blue | Basic solution |
| (ii) C + HCl\(_{(aq)}\) | Effervescence occurs colourless and odourless gas evolved gas which turns lime water milky | The gas is CO\(_2\) from CO\(_3^{2+}\) |
| (b)(i) D + NaOH\(_{(aq)}\) + Heat | Colourless gas evolved with characteristic chocking smell which turns litmus blue and form white fumes with conc. HCl acid stopper/Vapour |
Gas is NH\(_3\) NH\(_4^+\) present |
| (ii) D + water + BaCl\(_{2(aq)}\) and HCl |
It is soluble in water, white ppt. formed, ppt. dissolved forming a colourless soln. Colourless gas with irritating smell evolved; the gas turned the colour of acidified K\(_2\)Cr\(_2\)O\(_7\) or soln. from orange to green |
SO\(_3^{2-}\), SO\(_4^{2-}\) or CO\(^{2-}_3\) or S\(^{2-}\) present the gas is SO\(_2\) from SO\(_4^{2-}\) |