IMAT 2014 Q43 [pH Calculations]

What is the pH of 0.1 M HCl?

pH = - log_{10} [ H^+ ]

A. -0.1
B. -1
C. 0
D. 0.1
E. 1


What we can confidently assume when we first see this question, is the complete dissociation of HCl. Because it is a strong acid, we expect the composition of the acid to be in protons and chloride ions.

Next, we state the well known formula:

pH= -log_{10} (H^+)

With 0.1M of HCl, we should be able to say:

pH= -log_{10} (0.1) which is pH= -log_{10} (1\times10^1)

Therefore, pH= 1-log_{10} which is equal to 1. And our answer is E.