# Worksheet: Acid–Base Titrations

In this worksheet, we will practice describing the procedure for acid–base titrations, including choice of pH indicator and analysis of errors.

Q1:

If 35.23 mL of 0.250 M aqueous sodium hydroxide is required to titrate a 50.0 mL sample of hydrochloric acid, calculate the concentration of the hydrochloric acid.

Q2:

Potassium acid phthalate reacts with sodium hydroxide to form potassium sodium phthalate. A 0.2500 g sample of potassium acid phthalate requires 25.45 mL of a standard sodium hydroxide solution to react completely. Calculate the concentration of this solution to 3 significant figures.

Q3:

Potassium hydroxide reacts with dilute aqueous phosphoric acid to produce potassium hydrogen phosphate. Calculate the volume of a 0.1500 M solution of potassium hydroxide needed to titrate 40.00 mL of 0.06560 M aqueous phosphoric acid.

Q4:

In an acid-base titration, a 75.0 mL sample of a calcium hydroxide solution requires 36.6 mL of 50.0 mM hydrochloric acid to react completely. Calculate the molarity of the calcium hydroxide solution.

Q5:

Potassium hydroxide reacts with dilute sulfuric acid to produce aqueous potassium sulfate and water. Calculate the volume of an 8.83 mM solution of potassium hydroxide needed to react completely with 40.00 mL of 0.111 mM sulfuric acid.

Q6:

Oxalic acid reacts with aqueous sodium hydroxide to produce sodium oxalate and water. Calculate the volume of a 0.3300 M sodium hydroxide solution needed to titrate 15.00 mL of 0.1500 M oxalic acid.

Q7:

Nitric acid reacts with potassium hydrogen phosphate to produce potassium nitrate and phosphoric acid. Calculate, to 3 significant figures, the volume of 0.09992 M nitric acid needed to react completely with 0.3242 g of potassium hydrogen phosphate.

Q8:

Calculate the volume of 0.600 M hydrochloric acid needed to react completely with 2.50 g of sodium hydrogen carbonate.

Q9:

Which of the following statements about the equivalence point of an acid-base titration is true?

• AThe equivalence point of an acid-base titration is the point where there is an equivalent amount of titrant and titrand.
• BThe equivalence point of an acid-base titration is where the pH = 7.0 (neutral).
• CThe equivalence point of an acid-base titration is where the entire volume of the buret has been used.
• DThe equivalence point of an acid-base titration is the average value of the dissociation constants.
• EThe equivalence point of an acid-base titration is the same as the indicator endpoint.

Q10:

Why should a standard sodium hydroxide solution be titrated against a standard acid solution before use as a titrant?

• ASodium hydroxide reacts in water over time.
• BThe solution evaporates when stored under air.
• CSodium hydroxide precipitates over time.
• DThe solution reacts with atmospheric oxygen when stored under air.
• EThe solution reacts with atmospheric carbon dioxide when stored under air.

Q11:

When using phenolphthalein as an indicator in acid–base titrations, why is it better to use the base as the titrant?

• APhenolphthalein degrades more slowly in acid.
• BThe base solution degrades more slowly when stored in a buret.
• CA color change from colorless to pink is more easily detected than decolorization.
• DThe color change occurs more rapidly at low pH.
• EPhenolphthalein precipitates in base.

Q12:

A solution contains 40.0% of acetic acid by mass and has a density of 1.052 g/mL. What mass of calcium hydroxide is needed to neutralize 23.5 mL of this solution?

Q13:

If 1.70 mL of 0.0811 M aqueous sodium hydroxide is required to titrate a 20.0 mL aqueous solution of sulfuric acid, calculate the concentration of sulfuric acid in the sample.

Q14:

Calculate the volume of 0.0150 M hydrochloric acid needed to titrate 150 mL of 0.0200 M aqueous calcium hydroxide.

Q15:

Shown in the figure are the changes in pH as 0.100 M aqueous sodium hydroxide is added to a sample of hydrochloric acid.

To 3 significant figures, how many grams of are present in the analyte?

• A91.1 g
• B0.0911 g
• C0.365 g
• D0.255 g
• E3.65 g

Q16:

The figure shows the pH titration curve of 0.100 M against 0.100 M.

To the nearest milliliter, what was the initial volume of the solution?

Q17:

Shown in the figure are the changes in pH as 0.100 M aqueous sodium hydroxide is added to a 25 mL sample of hydrochloric acid.

To 3 significant figures, what was the initial concentration of in the analyte?

Q18:

Shown in the figure are the changes in pH as 0.100 M aqueous sodium hydroxide is added to a sample of hydrochloric acid.

To 3 significant figures, how many moles of are present in the analyte?

• A0.100 mol
• B mol
• C2.50 mol
• D mol
• E mol