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I am working on setting up an ICE table for adding 0.020 mol HCl to 1.0 L of 0.10 M propanoic acid. Since these are both acids (propanoic acid being the weaker one and HCl being strong), how would I set this up in an ICE table to calculate the pH of the resulting acid?
Edit: I was able to find an answer by taking the negative log of 0.02 to get the pH (because HCl is a strong acid). However, I am unaware with how to even set up the ICE table.
ICE tables tabulate amounts or concentrations pertaining to an equilibrium reaction: at the initial stage (I), how they change (C), and what they are at the end or at equilibrium (E). They are an alternative to solving multiple simultaneous equations (equilibrium constant expression, mass balance), instead using a single parameter (related to the extent of reaction $\xi$).
For the problem at hand, there is one reaction that goes to completion (strong acid) and one that attains equilibrium (weak acid, both protonated and deprotonated species present at equilibrium).
The ICE table needs to have species from the second reaction only. A good estimate of the hydrogen ion concentration is the concentration of hydrochloric acid (it dissociates completely, and we are ignoring the autodissociation of water for now).
$\begin{array}{|c|c|c|c|} \hline \ & [\ce{HP}] & [\ce{H+}] & [\ce{P-}]\\ \hline \text{I} & 0.1 & 0.02 & 0 \\ \text{C} & -x & +x & +x \\ \text{E} & 0.1-x & 0.02 +x & x\\ \hline \end{array}\\\\$
If you do the math, you will find that very little of the propanoic acid will dissociate, as the $\mathrm{p}K_\mathrm{a}$ is far from the initial pH.
