What is the pH of a 0.02 M HCl solution?

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Multiple Choice

What is the pH of a 0.02 M HCl solution?

Explanation:
The main idea is that a strong acid like HCl dissociates completely, so the hydrogen-ion concentration equals the acid concentration. The pH is the negative base-10 logarithm of [H+]. Here, [H+] = 0.02 M, so pH = -log10(0.02). Since log10(0.02) ≈ -1.699, the pH ≈ 1.70 (to three significant figures). Why other values don’t fit: a pH of 2.00 would mean [H+] ≈ 0.01 M; a pH of 1.30 would mean [H+] ≈ 0.050 M; a pH of 0.50 would mean [H+] ≈ 0.316 M. None match 0.02 M.

The main idea is that a strong acid like HCl dissociates completely, so the hydrogen-ion concentration equals the acid concentration. The pH is the negative base-10 logarithm of [H+].

Here, [H+] = 0.02 M, so pH = -log10(0.02). Since log10(0.02) ≈ -1.699, the pH ≈ 1.70 (to three significant figures).

Why other values don’t fit: a pH of 2.00 would mean [H+] ≈ 0.01 M; a pH of 1.30 would mean [H+] ≈ 0.050 M; a pH of 0.50 would mean [H+] ≈ 0.316 M. None match 0.02 M.

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