Multiple Choice
In healthy adults, what is the typical pH range of human skin (the “acid mantle”)?
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17. Acid and Base Equilibrium
The pH Scale
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On the pH scale, what does pH measure in an aqueous solution?
A
The hydroxide ion concentration, expressed as
B
The total concentration of dissolved salts (salinity) in the solution
C
The mass percent of acid present in the solution
D
The hydrogen ion concentration, expressed as
Verified step by step guidance1
Understand that pH is a measure of the acidity or basicity of an aqueous solution.
Recall that pH is defined based on the concentration of hydrogen ions (more precisely, hydronium ions, H\_3O\^+), not hydroxide ions or other components.
Use the formula for pH, which is given by the negative logarithm of the hydronium ion concentration: \(\displaystyle \text{pH} = -\log\left(\left[\mathrm{H_3O^+}\right]\right)\).
Recognize that this means as the concentration of hydronium ions increases, the pH decreases, indicating a more acidic solution.
Note that pH does not measure hydroxide ion concentration, total dissolved salts, or mass percent of acid, but specifically the hydrogen ion concentration expressed logarithmically.
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