Question

1) What is the pH (to nearest 0.01 pH unit) of a solution prepared by mixing 90.0 mL of 0.0509 M NaOH and 60.0 mL of 0.0400 M Ba(OH)2?

2) What is the pH (to nearest 0.01 pH unit) of a solution prepared by mixing 78.0 mL of 0.604 M HCl and 69.0 mL of 0.823 M NaOH?

3) Calculate the pH of each of the solutions and the change in pH to 0.01 pH units caused by adding 10.0 mL of 2.54-M HCl to 470. mL of each of the following solutions.

Change is defined as final minus initial, so if the pH drops upon mixing the change is negative.

a) water

pH before mixing =
pH after mixing=
pH change =

b) 0.178 M C₂H₃O₂^1-

pH before mixing =
pH after mixing=
pH change =

c) 0.178 M HC₂H₃O₂

pH before mixing =
pH after mixing=
pH change =

d) a buffer solution that is 0.178 M in each C₂H₃O₂^1- and HC₂H₃O₂

pH before mixing =
pH after mixing=
pH change =

4) Calculate the change in pH to 0.01 pH units caused by adding 10. mL of 2.60-M NaOH is added to 550. mL of each of the following solutions.

a) water

pH before mixing =
pH after mixing=
pH change =

b) 0.176 M NH₄¹⁺

pH before mixing =
pH after mixing=
pH change =

c) 0.176 M NH₃

pH before mixing =
pH after mixing=
pH change =

d) a buffer solution that is 0.176 M in each NH₄¹⁺ and NH₃

pH before mixing =
pH after mixing=
pH change =

5)

Consider the titration of 30.0 mL of 0.189-M of KX with 0.172-M HCl. The pK_a of HX = 8.59. Give all pH values to 0.01 pH units.

a) What is the pH of the original solution before addition of any acid?

pH =

b) How many mL of acid are required to reach the equivalence point?

V_A = mL

c) What is the pH at the equivalence point?

pH =

d) What is the pH of the solution after the addition of 11.2 mL of acid?

pH =

e) What is the pH of the solution after the addition of 39.6 mL of acid?

pH =

6)

A 4.543-g sample of a solid, weak, monoprotic acid is used to make 100.0 mL of solution. 15.0 mL of this solution was titrated with 0.07921-M NaOH. The pH after the addition of 28.38 mL of base was 5.60, and the equivalence point was reached with the addition of 48.60 mL of base.

a) How many millimoles of acid are in the original solid sample? Hint: Don't forget the dilution.

mmol acid

b) What is the molar mass of the acid?

g/mol

c) What is the pK_a of the acid?

pK_a =

A lot of these are similar problems, so if someone could let me know how to do them then I could probably figure the rest of them out. I was out of class the day we went over this and am completely lost.