(a) State the colour of the residue formed when nitrates of
1. Calcium 2. Zinc 3. Lead 4. Copper are strongly heated.
(b) Give one test each to distinguish between the following pairs of chemicals.
1. Zinc nitrate solution and calcium nitrate solution.
2. Sodium nitrate solution and sodium chloride solution.
3. Iron (III) chloride solution and copper chloride solution.