The process of heating an ore in the absence of air to remove volatile impurities is called:
A. Roasting
B. Calcination
C. Leaching
D. Smelting
Answer: Option B
Solution (By JKSSB Mock Tests)
Calcination involves heating an ore in limited supply or absence of air, often to convert carbonates/hydroxides to oxides and remove moisture or volatile impurities. Example: CaCO₃ → CaO + CO₂; Al(OH)₃ → Al₂O₃ + 3H₂O. Roasting is heating in excess air, usually for sulfide ores. Smelting uses reducing agents to obtain metal. Leaching uses chemicals.
Explanation:
According to Boyle's Law (P₁V₁ = P₂V₂), pressure and volume are inversely proportional at constant temperature. If the volume is doubled (V₂ = 2V₁), the pressure must be halved (P₂ = P₁/2) to keep the product constant. This demonstrates the inverse relationship between P and V.
Explanation:
Reduction can be defined as loss of oxygen, gain of hydrogen, gain of electrons, or decrease in oxidation number. All are correct definitions.
Explanation:
Calorific value is the amount of heat energy produced by complete combustion of unit mass of a fuel. SI unit is J/kg, often expressed as kJ/kg or MJ/kg. Previously, kcal/kg or cal/g was used. 1 cal = 4.184 J. Higher calorific value indicates better fuel. Example: hydrogen has very high calorific value ~150 MJ/kg. Exam note: Calorific value is measured by bomb calorimeter.
No comments yet. Be the first to start the discussion!