What is the pH of 0.010 mol/L hydrochloric acid, assuming complete dissociation?

### Why this is right Hydrochloric acid is a strong monoprotic acid, so the hydrogen-ion concentration is approximately $0.010$ mol/L, or $10^{-2}$ mol/L. Therefore, $pH = -\log_{10}(10^{-2}) = 2$. ### The other options - **1**: this corresponds to a hydrogen-ion concentration of about $0.1$ mol/L. - **3**: this corresponds to about $0.001$ mol/L. - **12**: this is alkaline, inconsistent with a strong acid solution. ### Worked numbers - **Given**: $[H^+] = 0.010$ mol/L. - **Find**: pH. - **Formula**: $pH = -\log_{10}[H^+]$. - **Solve**: $pH = -\log_{10}(0.010) = 2$. - **Answer**: pH is 2. - **Check**: an acid concentration of $10^{-2}$ mol/L gives pH 2. ### Terms - **pH**: the negative base-ten logarithm of hydrogen-ion concentration. - **Monoprotic acid**: an acid that donates one proton per molecule.