Explanation:
Acid rain results from SO₂ and NOₓ (oxides of nitrogen) dissolving in water vapor to form sulfuric and nitric acids. These are released from burning fossil fuels and industrial processes. Carbon dioxide forms weak carbonic acid (normal rain pH ~5.6), but SO₂ and NOₓ cause pH below 5.0.
Explanation:
Sodium reacts vigorously with moisture and oxygen in air, so it is stored under kerosene to prevent contact. Potassium, lithium are similarly stored. Iron, zinc, copper do not require such storage.
Explanation:
Permanent hardness is caused by dissolved chlorides and sulfates of calcium and magnesium. It cannot be removed by boiling. It is removed by adding washing soda (sodium carbonate, Na2CO3). The carbonate ions react with the soluble calcium and magnesium salts to form insoluble carbonates, which precipitate out.
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