Multiple Choice
What does the pH scale measure in an aqueous solution?
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17. Acid and Base Equilibrium
The pH Scale
Multiple Choice
At 25 °C, what is the pH of pure distilled water?
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Verified step by step guidance1
Understand that pure distilled water undergoes autoionization, where water molecules dissociate into H\(_3\)O\(^+\) (or H\(^+\)) and OH\(^-\) ions.
Recall that at 25°C, the ion product constant for water, K\(_w\), is 1.0 \(\times\) 10^{-14}, which means \(K\_w = [H^+][OH^-] = 1.0 \times 10^{-14}\).
Since pure water is neutral, the concentration of H\(^+\) ions equals the concentration of OH\(^-\) ions, so \([H^+] = [OH^-]\).
Set \([H^+] = x\), then \(x^2 = 1.0 \times 10^{-14}\), and solve for \(x\) to find the concentration of H\(^+\) ions in pure water.
Calculate the pH using the formula \(pH = -\log[H^+]\), which will give the pH of pure distilled water at 25°C.
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