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Answer: The pH of the solution is 9.68

Explanation:

To calculate the molarity of solution, we use the equation:

[tex]\text{Molarity of the solution}=\frac{\text{Mass of solute}}{\text{Molar mass of solute}\times \text{Volume of solution (in L)}}[/tex]

We are given:

Mass of solute (barium hydroxide) = 4.02 mg = 0.00402 g   (Conversion factor:  1 g = 1000 mg)

Molar mass of barium hydroxide = 171.34 g/mol

Volume of solution = 1 L

Putting values in above equation, we get:

[tex]\text{Molarity of solution}=\frac{0.00402g}{171.34g/mol\times 1L}\\\\\text{Molarity of solution}=2.4\times 10^{-5}M[/tex]

To calculate the pH of the solution, we need to determine pOH of the solution. To calculate pOH of the solution, we use the equation:

[tex]pOH=-\log[OH^-][/tex]

On complete dissociation, 1 mole of barium hydroxide produces 2 moles of hydroxide ions

We are given:

[tex][OH^-]=4.8\times 10^{-5}M[/tex]

Putting values in above equation, we get:

[tex]pOH=-\log(4.8\times 10^{-5})\\\\pOH=4.32[/tex]

To calculate pH of the solution, we use the equation:

[tex]pH+pOH=14\\pH=14-4.32=9.68[/tex]

Hence, the pH of the solution is 9.68

Considering the definition of pH, pOH and strong base, the pH of a 4.02 mg/L Ba(OH)₂ solution is 9.67.

You have a  4.02 mg/L Ba(OH)₂ solution. Being the molar mass (that is, the mass of one mole of a substance, which can be an element or a compound.) of barium hydroxide 171.34 g/mole, and being 1 mg=0.001 g then, the amount of moles that contain 4.02 mg of Ba(OH)₂ can be calculated as:

[tex]4.02 mgx\frac{0.001 grams}{1 mg} x\frac{1 mole}{171.34 grams} =[/tex] 2.35×10⁻⁵ moles

Then, the concentration of the Ba(OH)₂ solution is 2.35×10⁻⁵[tex]\frac{moles}{L}[/tex]=2.35×10⁻⁵ M.

On the other side, a Strong Base is that base that in an aqueous solution completely dissociates into the cation and hydroxide ion.

 

In this case, Ba(OH)₂ is a strong base. Then, the dissociation reaction will be:

Ba(OH)₂ → Ba²⁺ + 2 OH⁻

Since Ba(OH)₂ will completely dissociate in water, you can observe that the concentration of OH⁻ will be twice the concentration of Ba(OH)₂.

So, [OH⁻]= 2×2.35×10⁻⁵ M

[OH⁻]= 4.7×10⁻⁵ M

pOH is a measure of hydroxyl ions in a solution and is expressed as the logarithm of the concentration of OH⁻ ions, with the sign changed:

pOH= - log [OH⁻]

So, in this case:

pOH= - log (4.7×10⁻⁵ M)

pOH= 4.33

pH is a measure of acidity or alkalinity that indicates the amount of hydrogen ions present in a solution or substance.

The following relationship can be established between pH and pOH:

pH + pOH= 14

Being pOH= 4.33, pH is calculated as:

pH + 4.33= 14

pH= 14 - 4.33

pH= 9.67

Finally, the pH of a 4.02 mg/L Ba(OH)₂ solution is 9.67.

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