Question

The pH of saturated Sr(OH)2 is found to be 13.12. A 15.0ml sample of saturated Sr(OH)2 is diluted to 250.0ml in a volumetric flask. A 15.0ml sample of the diluted Sr(OH)2 is transferred to a beaker, and some water is added. The resulting solution requires 29.3ml of a HCl solution for its titration.

What is the molarity of this HCL solution?

Answer 1

The pH of the satd soln is 13.12; therefore, the pOH = 14 - 13.12 = 0.88
From this and pOH = -log(OH^-) you can find (OH^-) = about 0.12 (you need to do it exactly).
This was diluted from 15 mL to 250 so the (OH^-) in the 250 mL flask is 0.12 x 15/250 = about 0.0072 M (again you need to go through it to get a more exact answer).
So now you have a 15.0 mL sample of 0.0072 M OH^- titrated with 29.3 mL of ?M HCl.
mLbase x M base = mLacid x M acid.
Solve for M acid.