Why does the pH scale generally range from 0 to 14 in aqueous solutions?

• A. Because the pH scale is arbitrarily set to match the number of elements in the periodic table.
• B. Because the pH scale is based on the solubility of salts in water.
• C. Because water can only ionize to produce exactly 14 different pH values.
• D. Because the concentration of H^+ ions in water at 25°C typically varies between 1 mol/L and 1 × 10^{-14} mol/L.

Answer: (D)

Verified step by step guidance

1. Understand that the pH scale measures the acidity or basicity of an aqueous solution by quantifying the concentration of hydrogen ions (H\^+).
2. Recall that pH is defined mathematically as \(\mathrm{pH} = -\log_{10}[\mathrm{H}^\+ ]\), where \([\mathrm{H}^\+]\) is the molar concentration of hydrogen ions.
3. Recognize that pure water at 25°C undergoes autoionization, producing equal concentrations of H\^+ and OH\^- ions, each at about \$1 \times 10^{-7}$ mol/L, which corresponds to a neutral pH of 7.
4. Note that the concentration of H\^+ ions in aqueous solutions can vary widely, typically from 1 mol/L (very acidic, pH 0) to \$1 \times 10^{-14}$ mol/L (very basic, pH 14), which sets the practical range of the pH scale.
5. Conclude that the pH scale ranges from 0 to 14 because it reflects the logarithmic scale of hydrogen ion concentrations in water at 25°C, spanning from 1 mol/L to \$1 \times 10^{-14}$ mol/L.