Sagot :
SOLUTION:
Step 1: Calculate the hydroxide ion concentration at equilibrium.
The hydroxide ion concentration at equilibrium is twice the initial concentration of a strong base containing two OH.
[tex]\begin{aligned} [\text{OH}^-] & = 2[\text{Ba(OH)}_2]_{\text{initial}} \\ & = 2(0.020 \: M) \\ & = 0.040 \: M \end{aligned}[/tex]
Step 2: Calculate the pOH.
[tex]\begin{aligned} \text{pOH} & = -\text{log} \: [\text{OH}^-] \\ & = -\text{log} \: (0.040) \\ & = 1.40 \end{aligned}[/tex]
Step 3: Calculate the pH.
[tex]\begin{aligned} \text{pH} & = 14 - \text{pOH} \\ & = 14 - 1.40 \\ & = \boxed{12.60} \end{aligned}[/tex]
Hence, the pH of a 0.020 M Ba(OH)₂ solution is 12.60.
[tex]\\[/tex]
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