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 (KHCHO)844 reacts with sodium hydroxide to form potassium sodium phthalate. KHCHO()+NaOH()KNaCHO()+HO()8448442aqaqaql 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. HPO()+2KOHKHPO()+2HO()34242aqaql 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. HSO()+2KOH()KSO()+2HO()24242aqaqaql 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 (COH)242 reacts with aqueous sodium hydroxide to produce sodium oxalate and water. COH()+2NaOH()NaCO()+2HO()2422242aqaqaql 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. 2HNO()+KHPO()HPO()+2KNO()324343aqaqaqaq 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 HCl are present in the analyte?

  • A 9 . 1 1 × 1 0 g
  • B 0.255 g
  • C 3.65 g
  • D 0.365 g
  • E 91.1 g

Q16:

The figure shows the pH titration curve of 0.100 MNaOH against 0.100 MHCl.

To the nearest milliliter, what was the initial volume of the HCl 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 HCl 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 HCl are present in the analyte?

  • A0.100 mol
  • B 2 . 5 0 × 1 0 mol
  • C2.50 mol
  • D 1 . 0 0 × 1 0 mol
  • E 7 . 0 0 × 1 0 mol

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