Multiple Choice
On the pH scale, what does pH actually measure in an aqueous solution?
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17. Acid and Base Equilibrium
The pH Scale
Multiple Choice
On the pH scale, what quantity is measured for an aqueous solution?
A
The percentage of solute dissolved in the solution
B
The concentration of hydroxide ions, expressed as
C
The concentration of hydrogen ions, expressed as
D
The temperature of the solution in degrees Celsius
Verified step by step guidance1
Understand that the pH scale is a measure of the acidity or basicity of an aqueous solution.
Recall that pH is defined as the negative logarithm of the hydrogen ion concentration in the solution, mathematically expressed as \(\mathrm{pH} = -\log\left(\left[\mathrm{H_3O^+}\right]\right)\), where \(\left[\mathrm{H_3O^+}\right]\) is the molar concentration of hydronium ions.
Recognize that the hydronium ion \(\mathrm{H_3O^+}\) represents the hydrogen ion in aqueous solutions, which is responsible for acidity.
Note that the concentration of hydroxide ions \(\mathrm{OH^-}\) relates to basicity and is measured by pOH, not pH, where \(\mathrm{pOH} = -\log\left(\left[\mathrm{OH^-}\right]\right)\).
Conclude that the pH scale specifically measures the concentration of hydrogen ions (hydronium ions) in solution, not the percentage of solute dissolved or temperature.
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