Question

question regarding equivalence point and end point calculations:

how can i calculate the concentration of an unknown using a graph of ph values of a solution and ml of hcl? from the graph, i know that the equivalence point is 11 ml at ph 2.32.

similarly, how can i determine the concentration of the unknown using the indicator end point volume (which is 12.2ml at a ph of 1.26)

Answer 1

25 mL of 0.09607 M ammonia was titrated with unknown hydrochloric acid

Answer 2

For the NH3/HCl titration,
NH3 + HCl ==> NH4Cl
mL NH3 x M NH3 = millimols NH3.
From the equation, 1 mol NH3 = 1 mol HCl so mmols NH3 = mmols HCl
Then M HCl = mmols HCl/ml HCl used in the titration.
If I assume the 12.2 mL used with the indicator is the volume of HCl, then
(25 x 0.09607)/12.2 = M HCl

The calculation with the graph is the same but if these are for the same solutions, the agreement is lousy. Let me know if I have interpreted the question incorrectly and explain more fully.