Primary batteries are non-rechargeable; the chemical reaction that produces electricity cannot be reversed. The common dry cell (zinc-carbon battery) and alkaline batteries are primary cells. Lead-acid, Ni-Cd, and Li-ion are secondary (rechargeable) batteries where the reaction can be reversed by applying an external current.
Explanation:
Froth flotation separates sulfide ore particles from gangue by using oil and water. The ore particles adhere to the froth and float, while gangue sinks. Used for ZnS, PbS, CuFeS₂. Magnetic separation for magnetite, leaching for bauxite.
Explanation:
Atomic radius decreases across a period because the effective nuclear charge increases while electrons are added to the same shell, pulling the electron cloud closer. Down a group, radius increases due to addition of new shells.
Explanation:
Calorific value is determined using a bomb calorimeter, where a known mass of fuel is burnt in excess oxygen in a sealed bomb, and the heat released is absorbed by a known mass of water. Temperature rise is measured. Corrections for cooling, wire, and acid formation are applied. Units: kJ/kg or kJ/mol. The bomb calorimeter works at constant volume.
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