Unit 8: Topic 2 - pH and pOH of Strong Acids and Bases Flashcards

1
Q

What are strong acids and how do we calculate the pH of a strong acid solution?

A

When dissolved in an aqueous solution, strong acids dissociate completely into ions (H₃O⁺ and an anion). The seven most common strong acids are hydrochloric acid (HCl), hydrobromic acid (HBr), hydroiodic acid (HI), chloric acid (HClO₃), perchloric acid (HClO₄), sulfuric acid (H₂SO₄), and nitric acid (HNO₃).

The concentration of H₃O⁺ in a strong acid solution is equal to the initial concentration of the strong acid, so given a strong acid HA, pH of a strong acid solution = -log[HA].

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2
Q

What is the pH and pOH of a 0.0235 M HCl solution?

A

pH = 1.63
pOH = 12.37

HCl + H₂O -> H₃O⁺ + Cl⁻
pH = -log[H₃O⁺] = -log[HCl] = -log[0.0235] = 1.63
pOH = 14 - pH = 14 - 1.63 = 12.37

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3
Q

What are strong bases and how do we calculate the pH of a strong base solution?

A

When dissolved in an aqueous solution, strong bases dissociate completely into ions (OH⁻ and a cation). Strong bases are group I and II hydroxides.

The concentration of OH⁻ in a strong base solution is equal to the initial concentration of the strong base, so given a strong base BOH, pOH of a strong base solution = -log[BOH].

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4
Q

What is the pH of a 0.00705 M Ca(OH)₂ solution?

A

pH = 11.85

Ca(OH)₂ + H₂O -> Ca²⁺ + 2OH⁻
pH = 14 - pOH = 14 - (-log[OH⁻]) = 14 - (-log[Ca(OH)₂ = 14 - (-log[0.00705]) = 14 - 2.15 = 11.85

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