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 i.itne time they are made.
C is a sample of copper (II) tetraoxosulphate (VI) crystals. Carry out the following exercises on C. Record your observations and identify any gases evolved. State the conclusion you draw from the result of each test.
(a) Put half of C in a test tube and heat strongly
(b) Make solution of about 10 cm\(^{-3}\) with the sécond half of C and divide it into three portions
(i) To the first portion, add Sodium hydroxide solution in drops and then in excess. Heat the mixture
(ii) To the second portion, add aqueous ammonia in drops and then in excess followed by few drops of moderately concentrated HCI.
(iii) To the third portion, add all the zinc dust provided and stir thoroughly until there is a visible change.
Explanation
| Test | Observation | Inference |
| (a) C + Heat | Water droplets were observed first on the inner side of the test tube. A colourless gas with an irritating smell evolved which turns blue litmus red. | The water of crystalisation |
| (b) C + Water | It is soluble in water |
Soluble salts |
| (i) C + NaOH in drops and excess | A light pale blue ppt. insoluble in excess of NaOH was formed | CU\(^{2+}\) are present |
| (ii) C + NH\(_4\)OH and a few drops of Conc. HCL | A blue ppt is formed which is insoluble in HCL |
Cu\(^{2+}\) are present |
| (iii) Zinc + C in solution | The colour changed from blue to colourless | Displacement reaction |