A student has three unknown solutions (A, B, and C) with pH values of 2, 7 & 9.5 respectively. The solution with maximum hydrogen ion concentration is-

pH is a number that represents whether a solution is acidic or not.

It is represented as-

$$\begin{gathered} \mathrm{pH} = -\log \left[{\mathrm{H}}^{+}\right] \\ \mathrm{or} \\ \mathrm{pH} = - \log \left[{\mathrm{H}}_3{\mathrm{O}}^{+}\right] \end{gathered}$$

A very high hydrogen (${\mathrm{H}}_3{\mathrm{O}}^{+}$) concentration is represented by a low pH indicating that the solution is highly acidic in nature.

As solution A has the lowest pH, that means it has the highest hydrogen ion concentration among the given solutions.

Hence, The solution with maximum hydrogen concentration is A.