Metals And Non-metals Test - 2

Noble metals like gold and platinum are soluble in aqua regia, which is a mixture of conc. HCl (3 parts) and HNO₃ (1 part).

HNO₃ + 3HCl → 2[Cl] + NOCl + 2H₂O

Au + 3[Cl] → AuCl₃

AuCl₃ + HCl → H⁺[AuCl₄]^-

Metal + H₂O(g) → Metal oxide + H₂(g)
Metal + H₂O(l) → Metal hydroxide + H₂(g)

3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g)
Fe₃O₄ is a mixture of FeO and Fe₂O₃.
Hence, Fe(OH)₂ is not formed.

Na is a reactive metal and reacts violently with O₂ and H₂O in the air to form H₂ gas, which immediately catches fire by acquiring its ignition temperature on gaining heat from the exothermic reaction. Therefore, Na is preserved under kerosene oil.

Phosphorus is a reactive non-metal and reacts violently with O₂ in the air. However, it does not react with water and is hence preserved under water.

The substance reduced acts as the oxidising agent.

NH₄Cl has all covalent, coordinate and ionic bonds.
NH₃ has three covalent bonds. (N-H)
NH₄⁺ is formed by a coordinate bond. (H₃N:H⁺)
NH₄⁺Cl^- is formed by an ionic bond between the ammonium and the chloride ion.

Ag reacts with H₂S in the air to form silver sulphide.

Gunpowder, one of the earliest known chemical explosives, is a mixture of charcoal, sulphur and potassium nitrate.

Gallium is a metalloid, which is ductile and not malleable.

Calcination is the heating of the carbonate ores in the absence of air to form the corresponding oxides.

CaCO₃(s) → CaO(s) + CO₂(g)

Pyrolusite ore (MnO₂) cannot be reduced by carbon as Mn is a stronger reducing agent than carbon.

Carbon is a stronger reducing agent than Zn, Fe and Cu and can therefore reduce their oxides to obtain pure metal.

However, Cu₂O undergoes auto reduction and does not require any other reducing agent.