On the pH scale, pH is a measure of which quantity in an aqueous solution?

• A. The solution density, $\rho =\frac{m}{V}$
• B. The hydrogen ion concentration, $\left[H^{+}\right]$ (related by $pH=-\log \left(\left[H^{+}\right]\right)$)
• C. The total volume of solution in liters, $V\left(L\right)$
• D. The hydroxide ion concentration, $\left[O^H\right]$

Answer: (B)