17.3.1 Strong Acid-Strong Base Titration

Question 1

Strong Acid-Strong Base Titration

Answer 1

• Assuming a known mass of a pure acid, a titration can be used to determine the molecular weight and thus the identity of the unknown acid.
• The rate of change of pH along the titration curve is slight at the beginning, but dramatic as the solution approaches its equivalence point.

Question 2

note

Answer 2

• Assuming a known mass of a pure acid, a titration can be used to determine the molecular weight and thus the identity of the unknown acid.
• Completely neutralizing the unknown acid with sodium hydroxide (NaOH) means the number of moles of OH – used as a titrant is equal to the number of moles of H + .
• Assuming a monoprotic acid, this number of moles of H + ion will be equal to the number of moles of the unknown, from which the molecular weight and identity of the unknown can be derived.
• At the beginning of the titration of a strong acid, any
  strong base introduced into the system consumes some of the H + ion available from the fully dissociated strong acid causing the pH to rise slightly.
• The rate of change of pH along the titration curve is slight at the beginning, but dramatic as the solution approaches its equivalence point.
• At the equivalence point, the available acid has been entirely consumed by the strong base and the pH of the system jumps dramatically.
• In the case of a strong acid-strong base titration the result is a neutral solution with a pH of 7.0. In the case of a titration of a weak acid the equivalence point will not be at pH = 7.0.

Question 3

Look at the curve for the titration of HCl with NaOH.

Which statement is not correct?

Answer 3

During stage D, the pH of the solution and the volume of NaOH increase significantly in a steady manner.

Question 4

Suppose you have a 59 mL solution of 0.14 M HCl that is being titrated with 0.19 M NaOH. Before the equivalence point, you stop the titration. At this point, 25 mL of NaOH have been added. What is the change in pH at this point?

Answer 4

0.59

Question 5

Look at the graph, titration of HCl. Which statement about this graph is not true?

Answer 5

The equivalence point is the halfway point for stage B.

Question 6

Look at the curve for the titration of HCl with NaOH.

Various titration stages (A–D) are shown. Which statement about stage A is not correct?

Answer 6

The concentration of H + that is not bonded to the OH − ions remains fairly constant.

Question 7

The equivalence point in a titration reaction is _________________

Answer 7

the point at which the stoichiometric amount of the standardized solution has been added to the unknown solution.

Question 8

Which statement about the titration of a strong acid is not true?

Answer 8

After the solution has been neutralized, adding more OH − to the solution will not change the pH very much.

Question 9

Which statement best explains titration?

Answer 9

Titration is the process of adding a known concentration of solution to an unknown solution in order to determine its concentration.

Question 10

Suppose that you have a 72 mL solution of 0.15 M HCl that is being titrated with 0.24 M NaOH. Well before the equivalence point, you stop the titration. At this point, 33 mL of NaOH have been added. Which statement about the reaction is not correct?

Answer 10

The original amount of H + is 0.0015 moles. The final (at the point when the titration is stopped) amount of H + is 0.0080 moles.

Question 11

Which statement about the titration of a strong acid is not true?

Answer 11

The unknown is the strong base that is added in the titration event.

Question 12

Which statement about titration is not true?

Answer 12

When a titration begins, the pH is generally changed by a significant amount.