action of heat on solids

Question 1

thermal decomposition

Answer 1

carbonate –> oxide + carbon dioxide
nitrate –> oxide + nitrogen dioxide
sulfite –> oxide + sulfur dioxide
hydroxide –> metal oxide + water

Question 2

loss of water(s) of crystallisation

Answer 2

hydrated salts are ionic compounds that contain water within their crystal structure, known as waters of crystallisation. when a hydrated salt is heated, its water of crystallisation will be expelled as water vapour, leaving the anhydrous salt behind.

• identity of gas
• changes in colour of solid and colour of residue (hot & cold) –> cation

Question 3

thermal stability of metal compounds

Answer 3

more reactive –> more thermally stable –> harder to decompose
heat on oxide: potassium to copper stable; mercury to gold decomposed to the metal
heat on hydroxide: potassium + sodium stable; calcium to copper decomposed to metal oxide and water; mercury to gold hydroxides don’t exist
heat on carbonate: potassium + sodium stable; calcium to copper decomposed to metal oxide and carbon dioxide; mercury to gold decomposed to metal, carbon dioxide and oxygen