Ionic Equilibrium

Calculate the pH of a solution which contains 100mL of 0.1M $\ce{HCl}$ and 9.9mL of 1.0M $\ce{NaOH}$.


While calculating the concentration of $\ce{H+}$ ions, why shouldn't we consider the H+ ion concentration from water?




You **can** consider the hydrogen ion concentration from the ionization of water. However, that quantity is a million fold less than the amount of hydrogen ion coming from $\ce{HCl}$ and can be considered insignificant.


Incidentally, in this problem you could ask the same question about hydroxide from the ionization of water, and you'd find that the added hydroxide is ten-million fold greater than from the ionization of water.


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