Determine the pH of a 0.10 M MgCl2 solution.
Mg(H2O)62+ + H2O ==> Mg(H2O)5)(OH)+ + H3O
Set up an ICE chart, substitute into K and solve for H3O^+ then convert to pH.
1.7
To determine the pH of a solution, we first need to identify if the compound is an acid, a base, or a neutral compound.
MgCl2 is a neutral compound because it does not have any acidic or basic properties. Therefore, it will not affect the pH of the solution.
The pH of a neutral solution is 7. Therefore, the pH of a 0.10 M MgCl2 solution would also be 7.
To determine the pH of a solution, we first need to identify whether the solute is an acid or a base. In this case, MgCl2 is a salt that dissociates into ions in water, but it does not contain any hydrogen ions (H+). Therefore, it is neither an acid nor a base.
Since MgCl2 does not contribute any H+ ions, it will not directly affect the pH of the solution. However, the chloride ions (Cl-) can have an indirect effect on the pH by reacting with water and producing HClO, which is a weak acid.
To determine the pH of a solution containing MgCl2, we need to consider the hydrolysis reaction of the chloride ions with water. As mentioned, chloride ions can react with water to form HClO. The hydrolysis of chloride ions is an equilibrium reaction:
Cl- + H2O ⇌ HClO + OH-
Since HClO is a weak acid, it will partially dissociate and produce H+ ions:
HClO ⇌ H+ + ClO-
The concentration of H+ ions determines the pH of the solution.
The equilibrium constant expression for the hydrolysis of chloride ions can be represented as:
Kw = [H+][OH-]
But in this case, the concentration of hydroxide ions (OH-) is negligible because the solution is not basic. Therefore, we can assume [OH-] ≈ 0.
Thus, the equilibrium constant expression becomes:
Kw = [H+][0]
Given that the concentration of H+ ions is what determines the pH, we need to find the concentration of H+ ions in the solution.
Since we have a 0.10 M MgCl2 solution, we can assume that the concentration of chloride ions (Cl-) is also 0.10 M.
It's important to note that the hydrolysis reaction occurs in a 1:1 ratio. This means that for every chloride ion (Cl-) that reacts with water, one H+ ion is produced.
Therefore, the concentration of H+ ions is also 0.10 M.
Now, using the concentration of H+ ions, we can calculate the pH using the formula:
pH = -log[H+]
pH = -log(0.10)
Using a calculator, the pH of the 0.10 M MgCl2 solution is approximately 1.00.
So, the pH of the 0.10 M MgCl2 solution is 1.00.