Calculate the pH at the equivalence point for the titration of 0.130M methalamine (CH3NH2) with 0.13M Hcl. The Kb of methyl amine is 5.0x10-4.

Answer 1

CH3NH2 + HCl ==> CH3NH3Cl

At the equivalence point the (salt) = 1/2* 0.130 = 0.065 M.
.....CH3NH3^+ + H2O ==> CH3NH2 + H3O^+
I...0.065.................0........0
C......-x.................x........x
E....0.065-x..............x.........x

Ka for CH3NH3^+ = (Kw/Kb for CH3NH2) = (CH3NH2)(H2O^+)/(CH3NH3^+)
Substitute from the ICE chart and solve for x = (H3O^+) and convert to pH.

Answer 2

I keep getting 5.17 pH. but that's wrong.

do I use the equilibrium values to plug into the equation?

Answer 3

It gives me 5.94 for pH.

Answer 4

yes. It gives me 5.94 for pH.

Answer 5

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