Analytical Chemistry: Titration Overview

There are two types of metal hydroxides, soluble metal hydroxides and insoluble hydroxides, both of which are strong bases. Which of the following statements is NOT true for strong bases?

• Dilute solutions are completely dissociated.

• For strong base solutions with concentrations greater than or equal to 10^-6 M, the pOH is calculated from the concentration of the strong base.

• Fe(OH) is a strong soluble base.

• For strong base solutions with a concentration between 10^-6 and 10^-8 M, the pOH is determined using systematic equilibrium.

• For strong base solutions with concentrations less than or equal to 10^-8 M, the pOH is always 7.

A NaOH solution is standardized using the monoprotic primary standard potassium hydrogen phthalate, KHP (204.22 g/mol.) If 0.6986 g of KHP requires 43.92 mL of NaOH, what is the NaOH concentration? Report the answer in four decimal places without the unit.

• 0.0528

• 0.0613

• 0.0778

• 0.0892

Which is NOT a property of buffers?

• Buffers are a mixture of weak bases and conjugate acid.

• The pH of a buffer is independent of ionic strength.

• Buffers are a mixture of weak acid and conjugate base.

• Buffers resist changes in pH when acids or bases are added or when dilution occurs.

• The pH of a buffer is dependent on temperature.

A compound available in high purity, does not decompose under ordinary storage conditions and stable while being dried by heating or vacuum is a:

• secondary standard

• titrant

• indicator

• primary standard

• standard solution

25.0 mL of a 0.100 M solution of NH3 is titrated with 0.250M HCl. After 25.0 mL of the HCl has been added, the resultant solution is

• Basic and before the equivalence point

• Neutral and at the equivalence point

• Basic and after the equivalence point

• Acidic and before the equivalence point

• Acidic and after the equivalence point

A titration of an acid and base to the equivalence point results in a noticeably acidic solution. It is likely this titration involves

• a strong acid and a weak base

• a weak acid and a strong base

• a strong acid and a strong base

• a weak acid and a weak base (where Ka equals Kb)

Which of the following terms is INCORRECTLY defined?

• direct titration: titrant is added to analyte until reaction is complete

• standardization: titration of a known amount of analyte to determine the concentration of the titrant

• equivalent point: volume of titrant added in excess of the end point to change a physical property of the analyte solution

• titration error: the difference between the end point and the equivalent point

• blank titration: titration performed without analyte to calculate titration error

Consider the titrations of the pairs of aqueous acids and bases listed on the left. For which pair is the pH at the equivalence point stated incorrectly?

• A

• B

• C

• D

• E

A student is conducting molecular weight determination of an unknown diprotic acid. He first prepared a 250 mL of 0.15 M NaOH (39.997 g/mol) titrant solution, which he then standardized with 0.7625 g of KHP (204.22 g/mol) which consumed 26.32 mL of the titrant. After standardization, he weighed 0.0996 g of unknown diprotic acid and the titration reached the endpoint at a volume of 11.68 mL.

• 120.19

• 122.19

• 124.14

• 126.14

A student is conducting molecular weight determination of an unknown diprotic acid. He first prepared a 250 mL of 0.15 M NaOH (39.997 g/mol) titrant solution, which he then standardized with 0.7625 g of KHP (204.22 g/mol) which consumed 26.32 mL of the titrant. After standardization, he weighed 0.0996 g of unknown diprotic acid and the titration reached the endpoint at a volume of 11.68 mL.

• 0.0023

• 0.0037

• 0.0045

• 0.0059