titration

Examples of titration in the following topics:

• Weak Acid-Strong Base Titrations

  • A titration curve reflects the strength of the corresponding acid and base, showing the pH change during titration.
  • The titration curve demonstrating the pH change during the titration of the strong base with a weak acid shows that at the beginning, the pH changes very slowly and gradually.
  • This is due to the production of conjugate base during the titration.
  • This figure depicts the pH changes during a titration of a weak acid with a strong base.
  • Distinguish a weak acid-strong base titration from other types of titrations.

• Redox Titrations

  • As with acid-base titrations, a redox titration (also called an oxidation-reduction titration) can accurately determine the concentration of an unknown analyte by measuring it against a standardized titrant.
  • There are various other types of redox titrations that can be very useful.
  • This is called an iodometric titration.
  • A redox titration using potassium permanganate as the titrant.
  • Calculate the concentration of an unknown analyte by performing a redox titration.

• Strong Acid-Weak Base Titrations

  • The acid is typically titrated into the base.
  • In the case of titrating the acid into the base for a strong acid-weak base titration, the pH of the base will ordinarily start high and drop rapidly with the additions of acid.
  • In strong acid-weak base titrations, the pH at the equivalence point is not 7 but below it.
  • A depiction of the pH change during a titration of HCl solution into an ammonia solution.
  • Recall that strong acid-weak base titrations can be performed with either serving as the titrant.

• Acid-Base Titrations

  • Acid-base titration can determine the concentrations of unknown acid or base solutions.
  • Acid-base titrations can also be used to quantify the purity of chemicals.
  • This is the first titration and it is not very precise; it should be excluded from any calculations.
  • Record the initial and final readings on the burette, prior to starting the titration and at the end point, respectively.
  • The pH of a weak acid solution being titrated with a strong base solution can be found at each indicated point.

• Strong Acid-Strong Base Titrations

  • An acid-base titration is used to determine the unknown concentration of an acid or base by neutralizing it with an acid or base of known concentration.
  • A strong acid-strong base titration is performed using a phenolphthalein indicator.
  • Neutralization is the basis of titration.
  • Step 1: First calculate the number of moles of NaOH added during the titration.
  • Calculate the concentration of an unknown strong acid given the amount of base necessary to titrate it.

• Polyprotic Acid Titrations

  • If a dilute solution of oxalic acid were titrated with a sodium hydroxide solution, the protons would react in a stepwise neutralization reaction.
  • If the pH of this titration were recorded and plotted against the volume of NaOH added, a very clear picture of the stepwise neutralization emerges, with very distinct equivalence points on the titration curves.
  • The titration of dilute oxalic acid with sodium hydroxide (NaOH) shows two distinct neutralization points due to the two protons.
  • Recall the general shape of a pH vs equivalents graph generated by titrating a polyprotic acid.

• Acid-Base Indicators

  • pH indicators are frequently employed in titrations in analytical chemistry and biology to determine the extent of a chemical reaction.
  • In the titration of a weak acid with a strong base, which indicator would be the best choice?
  • In the titration of a weak acid with a strong base, the conjugate base of the weak acid will make the pH at the equivalence point greater than 7.
  • Common indicators for pH indication or titration endpoints is given, with high, low, and transition pH colors.
  • Explain which, of a given series, would be the best acid-base indicator for a given titration.

• Buffer Range and Capacity

  • This represents the point in the titration that is halfway to the equivalence point.
  • A titration curve visually demonstrates buffer capacity.

• Diprotic and Polyprotic Acids

  • Diprotic and polyprotic acids show unique profiles in titration experiments, where a pH versus titrant volume curve clearly shows two equivalence points for the acid; this is because the two ionizing hydrogens do not dissociate from the acid at the same time.
  • The titration curve of a polyprotic acid has multiple equivalence points, one for each proton.

• α-Amino Acids

  • The titration curve for alanine, shown below, demonstrates this relationship.
  • Titration curves show the neutralization of these acids by added base, and the change in pH during the titration.
  • Titration curves for many other amino acids may be examined at a useful site provided by The University of Virginia in Charlottesville; click on the following link (http://cti.itc.virginia.edu/~cmg/Demo/titr.html).
  • As expected, such compounds display three inflection points in their titration curves, illustrated by the titrations of arginine and aspartic acid shown below.
  • Formulas for these species are written to the right of the titration curves, together with the pH at which each is expected to predominate.