Question

Instead of calcium hydroxide, why don't we simply add sodium hydroxide to seawater to precipitate magnesium hydroxide?
A.The solubility of $Ca{\left( {OH} \right)_2}$ IS higher than that of $NaOH$
B.$NaOH$ may dissolve $Mg{\left( {OH} \right)_2}$ formed.
C.$NaOH$ may also precipitate other species
D.$NaOH$ being a weak electrolyte will not coagulate $Mg{\left( {OH} \right)_2}$

Answer 1

To answer this question, you should recall the properties of calcium hydroxide. Important raw material in preparation is calcium oxide. Quick lime shows the formula $CaO$. Calcium oxide production usually involves thermal decomposition of raw materials like limestone or seashells that contain calcium carbonate. Sodium hydroxide is a strong base, thus, it is very reactive as well.

Complete step by step answer:
Calcium hydroxide is known as slaked lime which has a white, powdery appearance in its solid-state. Caustic soda is a strong base and chemical name of sodium hydroxide. It is corrosive and finds application as a raw material in the manufacturing of washing soda and soda-lime. As $NaOH$ is stronger electrolyte than $Ca{\left( {OH} \right)_2}$, It can provide a large number of hydroxide ions compared to calcium hydroxide due to this fact it can precipitate other species.

Hence, the correct option is option C.

Additional information:
Slaked lime is prepared from calcium oxide. The important properties of Calcium Oxide:
Quick lime is an amorphous white solid with a high melting point of ${2600^o}C$. This shows that this is a very stable compound and can withstand high range temperatures.
The important reaction is the formation of slaked lime. This process is called the slaking of lime ${\mathbf{CaO}} + {{\mathbf{H}}_{\mathbf{2}}}{\mathbf{O}}{\text{ }} \to {\text{ }}{\mathbf{Ca}}{\text{ }}{\left( {{\mathbf{OH}}} \right)_{\mathbf{2}}}$
It is an oxide that is basic in nature and forms salts when it comes in contact with an acid.
This compound crystallizes in a cubic crystal lattice.

Note:
The standard molar entropy associated with calcium oxide corresponds to 40 joules per mole kelvin.
This compound is known to emit an intense glow when it is heated to temperatures above ${2400^o}C$.