MgO is used in making of the lining of Watt furnaces. It is extracted from seawater as follows. Aqueous calcium hydroxide is added to seawater:Ca(OH)(aq) MgCl2(aq) → Mg(OH)2(s) + CaCl2 (aq)Mg(OH)2 is then filtered off and roasted. Which of the following comparisons of calcium and magnesium explains why Mg(OH)2 is formed?
Correct answer: D. The solubility product of Mg(OH)2 is lower than that of Ca(OH)2
- A. Mg is less electropositive than calcium
- B. Mg is lower then Ca in the relative reactivity series
- C. The chance of hydration of Mg 2+ is less exothermic than of Ca2+
- D. The solubility product of Mg(OH)2 is lower than that of Ca(OH)2
Explanation
The solubility product (Ksp) is a measure of the equilibrium solubility of a compound in water. It is determined by the concentrations of the ions in the solution. A lower solubility product indicates lower solubility, meaning the compound is less soluble in water.In the reaction described, when calcium hydroxide (Ca(OH)2) is added to seawater containing magnesium chloride (MgCl2), a precipitation reaction occurs. The lower solubility product of Mg(OH)2 compared to Ca(OH)2 results in the formation of solid Mg(OH)2, which appears as a precipitate and can be filtered off. Therefore, option d is correct.
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