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Go to 15 weak acid/base titration problems

Return to twelve examples of weak acid/base titrations

**Example #1:** Consider the titration of a 24.0 mL sample of 0.105 M CH_{3}COOH with 0.130 M NaOH. What is . . .

(a) the initial pH?

(b) the volume of added base required to reach the equivalence point?

(c) the pH at 6.00 mL of added base?

(d) the pH at one-half of the equivalence point?

(e) the pH at the equivalence point?

**Example #2:** Calculate the pH, when the following solutions are added to 100. mL 0.10 M HClO solution:

(a) 0 mL 0.10 M NaOH

(b) 75.0 mL 0.10 M NaOH

(c) 100. mL 0.10 M NaOH

**Example #3:** 20.00 mL of a 0.150 M HCN solution is titrated with 0.100 M KOH solution. The K_{a} of HCN is 6.17 x 10¯^{10}.

(a) What is the initial pH of the HCN solution?

(b) What is the volume of KOH needed to reach the equivalence point?

(c) What is the pH at the half-equivalence point?

(d) What is the pH of the solution after 20.00 mL of KOH is added?

(e) What is the pH at the equivalence point?

(f) What is the pH of the solution after 40.00 mL of KOH is added?

**Example #4:** 20.00 mL of 0.250 M propanoic acid, C_{3}H_{7}COOH, is titrated with 0.125 M NaOH. Calculate the pH for the following five situations after the indicated amount of NaOH solution has been added. The K_{a} of propanoic acid is 1.34 x 10¯^{5}

(a) 0 mL

(b) 10.00 mL

(c) 20.00 mL

(d) 40.00 mL

(e) 50.00 mL

**Example #5:** Consider the titration of 100.0 mL of 0.200 M CH_{3}NH_{2} by 0.100 M HCl. Calculate the pH for (a) through (f). (K_{b} for CH_{3}NH_{2} = 4.4 x 10¯^{4})

(a) after 0.0 mL of HCl added.

(b) after 20.0 mL of HCl added.

(c) after 65.0 mL of HCl added.

(d) at the equivalence point.

(e) after 300.0 mL of HCl added.

(f) At what volume of HCl added does the pH = 10.643?

**Example #6:** 500. mL of a solution containing 1.50 M NH_{3}(aq) is mixed with 500. mL of a solution containing 0.500 M of HCl(aq). (K_{b} for NH_{3} = 1.77 x 10¯^{5}). Dtermine the pH of:

(a) the final solution.

(b) the solution in (a) after 40.0 mL of 0.200 M NaOH has been added.

(c) the solution in (a) after 24.0 mL of 0.500 M HCl has been added.

**Example #7:** A titration of 35.00 mL of 0.1750 M pyridine using a 0.275 M HCl solution is carried out. Pyridine has a pK_{b} = 8.77

(a) What is the initial pH of the pyridine solution (prior to any acid added)

(b) What is the pH of the pyridine solution after the addition of 5.00 mL of HCl

(c) What is the volume of HCl added at the half-equivalence point

(d) What is the pH of the pyridine solution at the half-equivalence point

(e) What is the pH of the pyridine solution after the addition of 21.00 mL of HCl

(f) What is the pH of the pyridine solution at the equivalence point

(g) What is the pH of the pyridine solution after the addition of 26.00 mL of HCl

**Example #8:** A 0.750 M solution of aniline is prepared and then titrated with 0.450 M nitric acid. Consider the following questions.

(a) What is the pH of the initial solution? What are the conjugate acid and base in the initial solution?

(b) If you have 75.0 mL of the initial aniline solution, what volume of nitric acid must be added to reach the endpoint and what will the pH be at the end point?

(c) Determine the volume of nitric acid you must add to reach the midpoint of the buffer region and the pH at the midpoint of the buffer region.

(d) If you add 5.00 mL of nitric acid when at the midpoint of the buffer region, what is the new pH of the solution?

(e) What mass of anilinium chloride must you add to the original 75.0 mL of aniline to prepare a buffer whose pH is 5.00 ?

**Example #9:** Calculate the pH at the points indicated below if 50.0 mL of 0.100 M aniline hydrochloride is titrated with 0.185 M NaOH. (K_{a} for aniline hydrochloride is 2.4 x 10¯^{5})

C_{6}H_{5}NH_{3}^{+}(aq) + OH¯(aq) ---> C_{6}H_{5}NH_{2}(aq) + H_{2}O(ℓ)

(a) before the titration begins

(b) at the equivalence point

(c) at the midpoint of the titration

(d) after 20. mL of NaOH has been added

(e) after 30. mL of NaOH has been added

**Example #10:** Consider the titration of 20.0 mL of 0.243 M of KX with 0.106 M HCl. The pK_{a} of HX is 10.39. Give all pH values to 0.01 pH units.

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

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

(c) What is the pH at the equivalence point?

(d) What is the pH of the solution after the addition of 27.9 mL of acid?

(e) What is the pH of the solution after the addition of 55.0 mL of acid?

**Example #11:** Calculate the pH at the equivalence point for the titration of 0.180 M methylamine (CH_{3}NH_{2}) with 0.180 M HCl. The K_{b} of methylamine is 4.4 x 10¯^{4}.

**Example #12:** A 0.0370 M solution of ammonia was titrated with HCl to the equivalence point, where the total volume was 1.50 times the original volume. At what pH does the equivalence point occur? K_{b} of ammonia = 1.77 x 10¯^{5}.

**Problem #1:** Acetic acid is a weak monoprotic acid with K_{a} = 1.77 x 10¯^{5}. NaOH(s) was gradually added to 1.00 L of 0.0179 M acetic acid. (Assume no volume change occurs.)

(a) Calculate the pH of the solution after the addition of 0.0107 mol of NaOH(s).

(b) Calculate the pH of the solution after the addition of 0.0179 mol of NaOH(s).

(c) Calculate the pH of the solution after the addition of 0.0286 mol of NaOH(s).

**Problem #2:** Consider the titration of 30.0 mL of 0.166 M of KX with 0.154 M HCl. The pK_{a} of HX = 8.090. Give all pH values.

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

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

(c) What is the pH at the equivalence point?

(d) What is the pH of the solution after the addition of 22.3 mL of acid?

(e) What is the pH of the solution after the addition of 38.8 mL of acid?

**Problem #3:** A 25.0-mL solution of 0.100 M acetic acid is titrated with a 0.200 M NaOH solution. Calculate the pH after the following additions of the NaOH solution:

(a) 0.0 mL

(b) 5.00 mL

(c) 10.0 mL

(d) 12.5 mL

(e) 15.0 mL

**Problem #4:** Calculate the pH of the solution in each step list below for the titration of 500. mL of 0.0100 M acetic acid (pK_{a} = 4.752) with 0.0100 M KOH

(a) after 0 mL of the titrant have been added.

(b) after 250. mL of the titrant have been added.

(c) after 490. mL of the titrant have been added.

(d) after 500. mL of the titrant have been added.

(e) after 510. mL of the titrant have been added.

(f) after 750. mL of the titrant have been added.

**Problem #5:** A 108.6 mL sample of 0.100 M methylamine (CH_{3}NH_{2}, K_{b} = 4.4 x 10¯^{4}) is titrated with 0.250 M HNO_{3}. Calculate the pH after the addition of each of the following volumes of acid.

(a) 0.00 mL

(b) 21.72 mL

(c) 43.44 mL

(d) 65.20 mL

**Problem #6:** Calculate the pH for each of the cases in the titration of 25.0 mL of 0.210 M pyridine, C_{5}H_{5}N(aq) with 0.210 M HBr(aq). The pK_{b} of pyridine is 8.77.

(a) before addition of any HBr

(b) after addition of 12.5 mL of HBr

(c) after addition of 21.0 mL of HBr

(d) after addition of 25 mL of HBr

(e) after addition of 31.0 mL of HBr

**Problem #7:** What is the pH at the equivalence point in the titration of 0.250 M HX (K_{a} = 5.2 x 10¯^{6}) with 0.250 M KOH?

**Problem #8:** What is the pH at the equivalence point in the titration of 100.0 mL of 0.100 M HCN (K_{a} = 4.9 x 10¯^{10}) with 0.100 M NaOH?

**Problem #9:** What is the pH when 25.00 mL of 0.20 M CH_{3}COOH has been titrated with 40.0 mL of 0.10 M NaOH?

**Problem #10:** Calculate the pH at the equivalence point for the titration of 0.220 M methyl amine (CH_{3}NH_{2}) with 0.220 M HCl. The K_{b} of methylamine is 4.4 x 10¯^{4}.

**Problem #11:** 25.0 mL of 0.10 M acetic acid (HAc) is titrated with 0.10 M NaOH. What is the pH at the equivalence point?

**Problem #12:** A 24.60 mL sample of a 0.447 M aqueous hydrofluoric acid solution is titrated with a 0.328 M aqueous barium hydroxide solution. What is the pH at the equivalence point of this titration? The K_{a} of HF = 7.2 x 10¯^{4}.

**Problem #13:** A 29.6 mL sample of 0.243 M dimethylamine, (CH_{3})_{2}NH, is titrated with 0.243 M hydroiodic acid. Determine the pH after adding 12.9 mL of hydroiodic acid. K_{b} for (CH_{3})_{2}NH = 5.9 x 10¯^{4}.

**Problem #14:** A 46.2 mL sample of a 0.392 M aqueous hydrofluoric acid solution is titrated with a 0.476 M aqueous sodium hydroxide solution. What is the pH after 22.2 mL of base have been added? The K_{a} of HF = 7.2 x 10¯^{4}.

**Problem #15:** A 100. mL sample of 0.25 M CH_{3}NH_{2}(aq) is titrated with a 100. mL of 0.25 M HNO_{3}(aq). Determine the pH after the reaction is complete. (The K_{b} for methylamine is 4.4 x 10¯^{4})

Go to 15 weak acid/base titration problems