Respuesta :
Answer:
a) Decreasing the pH
Explanation:
What we need to know to solve this problem is that we have an equilibrium for the dissolution of Mg(OH)₂ and we are bringing changes and need to know which one will increase the solubility of this hydroxide.
From LeChateliers principle we know that after any change brought to the equilibrium, the system will react in such a way as to restore the equilibrium by minimizing the disturbance.
Lets see now how our equilibrium will react for the given changes:
a) Decreasing pH
Decreasing pH effectively means we are adding acid to the equilibrium. This acid will consume part of the hydroxide ion, and the system will then shift to to the production of some hydroxide to restore equilibrium.
Therefore Mg(OH)₂ will become more soluble.
b) Increasing the pH
Increasing the pH will have the opposite effect as in part A, and will shift the equilibrium to the reactant side precipitating some Mg(OH)₂
c) Adding NH₃
NH₃ is a weak base therefore it will produce some hydroxide ion governed by the equilibrium
NH₃ + H₂O ⇆ NH₄⁺ + OH⁻
Therefore the equilibrium will shift in the same manner as in part b), that is precipitating some Mg(OH)₂.
d) Addig Mg(NO₃)₂
Here we will be adding Mg²⁺ to the equilibrium, and the system will react to remove some of the added Mg²⁺ making the Mg(OH)₂ less soluble.
The solubility of Magnesium hydroxide has been increased by decrease in pH. Thus, option A is correct.
The reaction of dissociation of magnesium hydroxide has been mediated with the formation of magnesium and hydroxide ions. The condition when the reactant and product has been equal is termed as equilibrium condition.
The change in the concentration of product and reactant favors the reaction to proceed in forward or backward direction.
Factors affecting increase in solubility:
According to the Principle of equilibrium, with the increase in the concentration of reactants, the reaction proceed in forward direction. With the increase in the product concentration, the reaction process in backward direction.
The factors that favor the increase in dissociation of magnesium hydroxide or product formation are favoring the increase in the solubility of magnesium hydroxide.
The decrease in pH has been aided by the addition of hydrogen to the solution, that results in the consumption of hydroxide, and favors the forward reaction.
Thus, the solubility of Magnesium hydroxide has been increased by decrease in pH. Thus, option A is correct.
For more information about solubility, refer to the link:
https://brainly.com/question/13620168
