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What is the pH of a 0.46 mol dm⁻³ solution of potassium hydroxide at 298 K? (Kw = 1.0 x 10⁻¹⁴ mol² dm⁻⁶ at 298 K) - AQA - A-Level Chemistry - Question 10 - 2017 - Paper 3

Question 10

What is the pH of a 0.46 mol dm⁻³ solution of potassium hydroxide at 298 K? (Kw = 1.0 x 10⁻¹⁴ mol² dm⁻⁶ at 298 K)

Worked Solution & Example Answer:What is the pH of a 0.46 mol dm⁻³ solution of potassium hydroxide at 298 K? (Kw = 1.0 x 10⁻¹⁴ mol² dm⁻⁶ at 298 K) - AQA - A-Level Chemistry - Question 10 - 2017 - Paper 3

Step 1

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Answer

To find the pOH of a potassium hydroxide (KOH) solution, which is a strong base, we first determine the concentration of hydroxide ions (OH⁻).

Since KOH completely dissociates, the concentration of OH⁻ ions is the same as the concentration of KOH, which is 0.46 mol dm⁻³. Therefore,

[ \text{pOH} = -\log[\text{OH}^-] = -\log(0.46) \approx 0.336 ]

Step 2

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Answer

Next, we can calculate the pH using the relationship:

[ \text{pH} + \text{pOH} = 14 ]

Substituting the pOH value:

[ \text{pH} = 14 - \text{pOH} \approx 14 - 0.336 \approx 13.664 ]

Rounding this value gives us a pH of approximately 13.66.

Step 3

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Answer

Thus, the pH of the 0.46 mol dm⁻³ solution of potassium hydroxide at 298 K is approximately 13.66, which corresponds to option B.

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