[dkk]

I have trouble solving these questions please help me..


1)A compound has a pKa of 7.4. To 100mL of 1.0M solution this compound at pH 8.0 is added 30 mL of 1.0 M HCl. What is the pH of the resulting solution?

2) A compound is known to have a free amino group with a pKa of 8.8 and one other ionizable group with a pKa between 5 and 7. To 100mL of a 0.2 M solution this compound at pH 8.2 was added 40mL of a solution of 0.2 M HCl. The pH changed to 6.2.  The pKa of the second ionizable group is?

3) A 1.0 M solution of a compound with 2 ionizable groups (pka's 6.2 and 9.5; 100mL total) has a pH of 6.8. If a biochemist adds 60mL of 1.0M HCl to this solution, the solution will change to what pH?