Plaster of Paris (CaSO₄·½H₂O) sets by rehydrating to gypsum (CaSO₄·2H₂O) when mixed with water: CaSO₄·½H₂O + 1½H₂O → CaSO₄·2H₂O. The interlocking crystals of gypsum provide hardness. It expands slightly on setting, making it ideal for casting. Dehydration is the opposite. Oxidation and carbonation are not involved.
Explanation:
Calorific value is the amount of heat energy produced on the complete combustion of 1 kg (or 1 m³ for gases) of a fuel. It is expressed in kJ/kg or kJ/m³. Hydrogen has the highest calorific value among common fuels, making it a highly efficient energy source.
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.
Explanation:
Sodium lauryl sulfate (CH₃(CH₂)₁₁OSO₃Na) is a synthetic detergent with a sulfate group. Sodium stearate and potassium palmitate are soaps (carboxylate salts). Calcium oleate is soap scum.
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