4. The reaction goes
Zn+FeSO4 -> Fe + ZnSO4
Zinc is a silvery metallic solid, FeSO4 solution is generally light (dirty) green due to impurities. It is rare to find the pure version which in fact is colourless.
Fe (iron) deposits as a black powder, and aquous ZnSO4 solution is colourless (if there is sufficient or excess Zn present)
5. FeSO4 (light green) when heated will first lose the water of crystalization (mono-, penta-, hexa- and hepta-hydrates) to become a white anhydrous powder. On further heating, it will decompose as follows:
2FeSO4 -> Fe2O3 + SO2 + SO3.
Fe2O3 is a dark solid, SO2 is a gas that is produced when burning sulphur, and SO3 is the precursor to sulphuric acid (when added to water), so it is irritating.
6.
pH of (pure) water is 7
Ethanoic (acetic) acid at 5% is household vinegar. When at 5%, it has a pH of 2.4.
HCl is a strong acid, depending on concentration, a pH of 1 is not surprising.
NaOH is a strong alkali, so a pH of 13 is normal.
