Question

a. when 0.10 mol of the ionic sold NaX, where X is an unknown anion, is dissolved in enough water to make 1.0 L of solution, the pH of the solution is 9.12. When 0.10 mol of the ionic solid ACl, where A is an unknown cation, is dissolved in enough water to make 1.0 L of solution, the pH of the solution is 7. What would be the pH of the 1.0 L of solution that contained 0.10 mol of AX? Be sure to document how you arrived ar your answer.

b. In the AX solution prepared above, is there any OH- present? If so, compare the [OH-] in the solution to the [H3O+].

c. From the information presented in part A, calculate Kb for the X^- (aq) anion and Ka for the conjugate acid of X^- (aq).

d. To 1.0 L of solution that contains 0.10 mol of AX, you add 0.025 mol of HCl. How will the pH of this solution compare to that of the solution that contained only NaX? Use chemical reactions as part of your explanantion; you do not need to solve for a numerical answer.

e. Another 1.0 L sample of solution is prepared by mixing 0.10 mol of AX a d 0.10 mol of HCl. The pH of the resulting solution is found to be 3.12. Explain why the pH of this solution is 3.12.

f. Finally, consider a different 1.0 L sample of solution that contains 0.10 mol of AX and 0.1 mol of NaOH. The pH of this solution is found to be 13. Explain why the pH of this solution is 13.

g. Some students mistakenly think that a solution that contains 0.10 mol of AX and 0.10 mol of HCl should have a pH of 1.00. Can you come up with a reason why students have this misconception? Write an approach that you would use to help these students understand what they are doing wrong.

Answer 1