Complete The Following Solubility Constant Expression For Mg(OH)2.
The Correct Answer and Explanation is :
The solubility product constant (( K_{sp} )) expression for magnesium hydroxide (( Mg(OH)_2 )) is derived from its dissociation equation in aqueous solution:
[
Mg(OH)_2 (s) \rightleftharpoons Mg^{2+} (aq) + 2OH^- (aq)
]
The solubility product constant expression is given by:
[
K_{sp} = [Mg^{2+}][OH^-]^2
]
Explanation:
- Dissociation of ( Mg(OH)_2 )
Magnesium hydroxide is a slightly soluble salt in water. When it dissolves, it dissociates into magnesium ions (( Mg^{2+} )) and hydroxide ions (( OH^- )) in a 1:2 molar ratio. - Solubility Product Constant (( K_{sp} ))
The solubility product constant is a measure of the extent to which a compound dissolves in water. It is defined as the product of the equilibrium concentrations of the ions, each raised to the power of its stoichiometric coefficient in the balanced equation. - Why Solid ( Mg(OH)2 ) is Not Included in ( K{sp} )
Solubility equilibrium expressions do not include solids or pure liquids because their concentrations remain constant. The equilibrium expression only involves the concentrations of the dissolved ionic species. - Importance of ( K_{sp} )
- The ( K_{sp} ) value helps predict whether a precipitate will form when solutions containing ( Mg^{2+} ) and ( OH^- ) are mixed.
- A high ( K_{sp} ) value indicates greater solubility, while a low ( K_{sp} ) value means the compound is less soluble.
- Knowing ( K_{sp} ) allows chemists to calculate the solubility of ( Mg(OH)_2 ) in water.
- Application in Real Life
- Medicine: Magnesium hydroxide is used as an antacid and laxative (milk of magnesia).
- Water Treatment: It helps neutralize acidic water.
- Industrial Uses: Used in wastewater treatment to remove heavy metals.
Thus, the correct solubility constant expression for ( Mg(OH)_2 ) is:
[
K_{sp} = [Mg^{2+}][OH^-]^2
]