We’re being asked to calculate the pH of a 0.34 M weak acid with pKa of 5.40.
Remember that weak acids partially dissociate in water and that acids donate H+ to the base (water in this case). The dissociation of HA is as follows:
HA(aq) + H2O(l) ⇌ H3O+(aq) + A–(aq)
From this, we can construct an ICE table. Remember that liquids are ignored in the ICE table.
The Ka expression for HA is:
Note that each concentration is raised by the stoichiometric coefficient: [HA], [H3O+] and [A–] are raised to 1.
What is the pH of a 0.34 M solution of a weak acid which has a pKa of 5.40?
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