Lead-acid battery uses dilute sulfuric acid (H₂SO₄) as the electrolyte with lead dioxide (PbO₂) as positive plate and spongy lead (Pb) as negative plate. Discharge reaction: Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O. It is a secondary (rechargeable) battery used in automobiles. The specific gravity of electrolyte indicates the state of charge. KOH is used in Ni-Cd and alkaline batteries.
Explanation:
Soap (sodium carboxylate) reacts with Ca²⁺/Mg²⁺ to form insoluble calcium or magnesium carboxylate (scum). This precipitates and reduces cleaning efficiency. Sodium and potassium salts are soluble. This is why detergents, which form soluble Ca/Mg salts, are used. Scum is visible in hard water areas.
Explanation:
Saline water (containing NaCl) increases the electrical conductivity of the water, accelerating the electrochemical process of rusting. This is why ships and coastal structures rust faster. Dry air and vacuum have no moisture; pure water without dissolved oxygen slows rusting.
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