Assertion (A): Zinc can displace copper from copper sulfate solution. Reason (R): Zinc is more reactive than copper. MCQ with Answer and Explanation

Explanation:
Highly reactive metals (K, Na, Ca, Mg, Al) are extracted by electrolysis of their fused (molten) salts because chemical reducing agents cannot reduce their ores. For sodium, Down's process: electrolysis of molten NaCl with CaCl₂ to lower melting point. Iron is extracted by smelting (blast furnace). Copper and zinc can be extracted by reduction with coke or electrolytic refining of impure metal.

Explanation:
Washing soda (sodium carbonate, Na₂CO₃) is used to remove permanent hardness of water. It reacts with soluble calcium and magnesium chlorides/sulfates to form insoluble carbonates, which can be filtered out. Baking soda, bleaching powder, and plaster of Paris do not have this water-softening capability.

Explanation:
Rutherford's gold foil experiment (1911) showed that most of the atom is empty space with a dense positively charged nucleus. Thomson proposed the plum pudding model; Bohr gave quantized orbits; Dalton gave solid sphere model.