We can occupational out the concentrations of all the species at equilibrium by means of the ICE table.
You are watching: How to calculate ph of weak base
We deserve to then substitute these worths into the base dissociation constant (Kb) expression.
In order to deal with for x, we must impose an approximation to stop resolving quadratic equation.
We will certainly assume that the concentration of weak base at equilibrium is equal to its original concentration.
We have the right to then rearvariety the equation to determine x, which is the concentration of OH-.
Because we are dealing largely with monoprotic species in Ionic Equilibria, the ICE table and also approximation is constantly valid.
Because of this we deserve to use the following formula to conveniently recognize OH- concentration when Kb and weak base concentration are provided.
For this exercise Kb of ammonia is not given.
But we have the right to gain this conveniently from the Ka of its conjugate acid NH4+ and Kw, the ionic product of water.
Please note Ka.Kb = Kw just applies to conjugate acid-base pairs.
We can currently usage the formula method to find OH- concentration.
Finally we deserve to determine pOH and also pH of this weak base.
Topic: Ionic Equilibria, Physical Chemistry, A Level Chemistry, Singapore
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