1. Reactivity Series (Decreasing order): K > Na > Ca > Mg > Al > Zn > Fe > Ni
> Sn > Pb > [H] > Cu > Hg > Ag > Pt > Au.
2. Magnesium with Oxygen:
$2Mg(s) + O_2(g) \xrightarrow{\Delta} 2MgO(s)$
Burns with dazzling white flame, produces white ash (MgO).
3. Sodium with Water (Cold):
$2Na(s) + 2H_2O(l) \rightarrow 2NaOH(aq) + H_2(g) + Heat$
Vigorous reaction, H$_2$ may catch fire.
4. Iron with Steam:
$3Fe(s) + 4H_2O(g) \xrightarrow{\Delta} Fe_3O_4(s) + 4H_2(g)$
5. Zinc with Dilute H$_2$SO$_4$:
$Zn(s) + H_2SO_4(aq) \rightarrow ZnSO_4(aq) + H_2(g)$
6. Copper with Oxygen (Heating):
$2Cu(s) + O_2(g) \xrightarrow{\Delta} 2CuO(s)$ (Black)
7. Displacement (Iron in CuSO$_4$):
$Fe(s) + CuSO_4(aq) \rightarrow FeSO_4(aq) + Cu(s)$
Blue colour fades to green, Cu deposited.
8. Roasting: Heating ore in excess of air (for Sulphide
ores).
$2ZnS(s) + 3O_2(g) \xrightarrow{\Delta} 2ZnO(s) + 2SO_2(g)$
9. Calcination: Heating ore in limited/no air (for Carbonate
ores).
$ZnCO_3(s) \xrightarrow{\Delta} ZnO(s) + CO_2(g)$
10. Reduction with Carbon (Medium Reactivity):
$ZnO(s) + C(s) \xrightarrow{\Delta} Zn(s) + CO(g)$
11. Thermite Reaction (for Iron):
$Fe_2O_3(s) + 2Al(s) \xrightarrow{\Delta} 2Fe(l) + Al_2O_3(s) + Heat$
Used for welding railway tracks.
12. Electrolytic Reduction (High Reactivity - Al):
At Cathode: $Al^{3+} + 3e^- \rightarrow Al$. Sodium is extracted similarly from molten NaCl.
13. Corrosion: Slow eating away of metals by reaction with
air and moisture. Example: Rusting of Iron.
14. Rusting: $4Fe + 3O_2 + xH_2O \rightarrow 2Fe_2O_3 \cdot
xH_2O$ (Hydrated Iron(III) Oxide).
15. Prevention: Galvanisation (Zn coating), Electroplating
(Cr, Ni), Painting, Oiling, Making Alloys.
