The acceptable pH range for a particular acidic solution is between 1.2 and 1.5. What is the interval of molar hydrogen ion concentration of this acid solution?

Use pH = −log₁₀[H⁺], so [H⁺] = 10^(−pH). Because concentration decreases as pH increases, the pH range from 1.2 to 1.5 gives concentrations from 10^(−1.5) ≈ 0.0316 M to 10^(−1.2) ≈ 0.0631 M. Thus the interval is (0.0316, 0.0631), choice C.

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