Credit will be given for strict adherere 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 is a sample of iron (ii) tetraoxosulphate (VI). D is a sample of zinc trioxocarbonate (IV). Carry out the following exercises on C and D. Record your observations and identify any gases evolved. State the conclusion you draw from the result of each test.
(a)(i) Put all of C in a test tube and add about 5 cm\(^3\) of distilled water. Stir and test with litmus paper. Divide the solution into two portions
(ii) To the first portion, add sodium hydroxide solution in drops and then in excess.
(iii) To the second portion, add few drops of barium chloride solution, followed by dilute hydrochloric acid in excess.
(b)(i) Put half of D in a dry test tube and heat strongly. Allow to cool.
(ii) Add about 5 cm\(^3\) of dilute hydrochloric acid to the residue and divide the solution into two portions.
(iii) To the first portion, add sodium hydroxide solution in drops and then in excess.
(iv) To the second portion, add aqueous ammonia in drops and then in excess.
Explanation
| Test | Observation | Inference |
| (a)(i) C + H\(_2\)O + litmus paper | C dissolves, blue litmus paper turned red | soluble salt solution is acidic |
| (ii) Solution of C + NaOH\(_{(aq)}\) in drops + excess | Dirty green ppt. ppt insoluble in excess | |
| (iii) Solution of C + BaCl\(_{2(aq)}\) + dil. HCl | White ppt. ppt is insoluble in dil. HCl | |
| (b)(i) D + heat | D changes from white to yellow and turned to white on cooling, colourless gas evolved, gas turned lime water milky | |
| (ii) Residue + dil. HCl | Gas evolved. Residue dissolves from a colourless solution | |
| (iii) Solution + NaOH from b(ii) in drops + excess | White gelatinous ppt. ppt soluble in excess or ppt. dissolves. | |
| (iv) Solution (b)(ii) + NH\(_{3(aq)}\) + excess | White gelatinous ppt, ppt soluble in excess or ppt. dissolved |