Problem: Solve an equilibrium problem (using an ICE table) to calculate the pH of each of the following solutions.0.16 M CH3 NH3 Cl

FREE Expert Solution

We’re being asked to calculate the pH of a 0.16 M CH3NH3Cl using an ICE chart.


CH3NH3+ is a conjugate acid of the base CH3NH2. We need to use the Kb for CH3NH2 to find the Ka of its conjugate acid, CH3NH3+. Let us just omit Clsince it is neutral.


We can find on books and the internet that the Kb of CH3NH2 is 4.4x10-4. Therefore, the Ka of CH3NH3+ is:


Kw = KaKbKa = KwKbKa = 1.0×10-144.4×10-4

Ka = 2.27x10-11


Since CH3NH3+ has a very low Ka value, it’s a weak acid. Remember that weak acids partially dissociate in water and that acids donate H+ to the base (water in this case). The dissociation of CH3NH3+ is as follows:


CH3NH3+(aq) + H2O(l)  H3O+(aq) + CH3NH2(aq); Ka = 2.27×10–11


From this, we can construct an ICE table. Remember that liquids are ignored in the ICE table.



The Ka expression for CH3NH3+ is:


Ka=[H3O+][CH3NH2][CH3NH3+]

Liquids are ignored in the Ka expression.


Note that each concentration is raised by the stoichiometric coefficient: [CH3NH3+], [H3O+] and [CH3NH2] are raised to 1.


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Problem Details

Solve an equilibrium problem (using an ICE table) to calculate the pH of each of the following solutions.

0.16 M CH3 NH3 Cl