A quantitative method that uses a solution of known concentration to determine the concentration of an analyte.

What is a titration curve?

A graph of a solution property, commonly pH, versus the amount or volume of titrant added.

How is the equivalence point defined?

It is the point at which titrant and sample have reacted in the stoichiometric proportions of the balanced reaction.

How is pH found before equivalence for a strong acid titrated with strong base?

Subtract the base moles reacted from the initial acid moles, divide the excess acid moles by total volume to find $[H_3O^+]$, and calculate $pH=-\log[H_3O^+]$.

How is pH found after equivalence for a strong acid–strong base titration?

Find the excess hydroxide moles, divide by total volume, calculate pOH, and use $pH=14.00-pOH$ at $25^\circ\text{C}$.

Analytical chemistryLesson 2 of 2 in the course Acid-Base Equilibria

Acid–Base Titrations: Stoichiometry, Curves, and Indicators

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Acid-base titrations use a measured solution to determine the concentration of an acid or base. This lesson introduces titration curves and shows how to calculate pH during a strong acid–strong base titration by tracking neutralization stoichiometry.

A titration curve plots a solution property, commonly pH, against the volume of titrant added. Since pH changes as the amounts of acid and base change, the curve helps reveal the titration's progress and equivalence region.

All flashcards

What is a titration?: A quantitative method that uses a solution of known concentration to determine the concentration of an analyte.
What is a titration curve?: A graph of a solution property, commonly pH, versus the amount or volume of titrant added.
How is the equivalence point defined?: It is the point at which titrant and sample have reacted in the stoichiometric proportions of the balanced reaction.
How is pH found before equivalence for a strong acid titrated with strong base?: Subtract the base moles reacted from the initial acid moles, divide the excess acid moles by total volume to find $[H_3O^+]$ , and calculate $pH=-\log[H_3O^+]$ .
How is pH found after equivalence for a strong acid–strong base titration?: Find the excess hydroxide moles, divide by total volume, calculate pOH, and use $pH=14.00-pOH$ at $25^\circ\text{C}$ .

Quiz questions

For an acid-form indicator represented by $HIn \rightleftharpoons H_3O^+ + In^-$ , which form predominates when the solution pH is well above the indicator's $pK_a$ ?Answer: The conjugate-base form, $In^-$
Which indicator is suitable for a weak-acid–strong-base titration because its color-change interval overlaps the basic equivalence region?Answer: Phenolphthalein
What is the difference between an indicator endpoint and a titration equivalence point?Answer: The endpoint is the observed color change; equivalence is the stoichiometric point.
Why is the equivalence-point solution basic when a weak acid is titrated with a strong base?Answer: The conjugate base reacts with water to produce hydroxide ions.
After equivalence, why can strong-acid and weak-acid titration curves using the same strong base become similar?Answer: Excess hydroxide largely controls pH in both solutions.

Based on Chemistry 2e by Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson, PhD (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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