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4.6Chemical Reactions

Introduction to Titration — AP CHEMISTRY Revision Notes & Topical Questions

5 min read 9 parts Lesson 9 of 12 1 quiz

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Lesson summary

4.6 Introduction to Titration — Notes — AP CHEMISTRY notes: Use titration to determine the amount of an analyte and identify equivalence and end points.A titration determines the amount of an analyte in solution.The titrant is a solution of known concentration, held in the burett…

  • Equivalence point
  • Moles of titrant
  • For a 1:1 reaction M1V1
  • Concentration of analyte
  • Volumetric pipette
  • Volumetric flask

Section 1 of 9Principle of titration

1
A titration determines the amount of an analyte in solution.
2
The titrant is a solution of known concentration, held in the burette, that reacts specifically and quantitatively with the analyte.
3
The titrant is added to a measured volume of analyte until the reaction is exactly complete.
4
Types include acid-base and redox titrations.

Section 2 of 9Equivalence point and end point

Equivalence point
Equivalence point the point at which the moles of titrant are stoichiometrically equivalent to the moles of analyte.
End point
End point the point at which the indicator changes colour or a sensor shows a sharp change.
A well-chosen indicator makes the end point very close to the equivalence point.
On a pH curve the equivalence point is at the steepest part (inflection point).

Section 3 of 9Calculation

Moles of titrant
M × V, with V = final burette reading − initial burette reading, in litres.
At the equivalence point, moles of titrant × (analyte coefficient ÷ titrant coefficient) = moles of analyte.
For a 1:1 reaction M1V1
M2V2.
Concentration of analyte
Concentration of analyte moles of analyte ÷ volume of analyte.

Section 4 of 9Glassware

Burette
  • Burette delivers variable volumes precisely, read at the bottom of the meniscus.
Volumetric pipette
  • Volumetric pipette delivers a fixed volume of analyte.
Volumetric flask
  • Volumetric flask prepares a standard solution.

Section 5 of 9Technique and errors

1
Rinse the burette with titrant and the pipette with analyte, because rinsing with water would dilute them.
2
Adding water to the analyte flask does not change the moles of analyte, so it does not affect the result.
3
If the titrant is diluted, more volume is needed, so the calculated analyte concentration is too high.
4
Overshooting the end point also gives a result that is too high.

Section 6 of 9Redox titrations

Redox titrations
They work in the same way, using the mole ratio from the balanced redox equation.
Permanganate acts as its own indicator, because its purple colour persists at the end point.

Section 7 of 9More from the specification

More from the specification
Product
  • A substance formed in a reaction.
Significant figures
  • The digits in a value that are reliable and carry meaning.
Percent yield
  • Actual yield divided by theoretical yield, times 100.
Limiting reactant
  • The reactant that is used up first and so limits the amount of product.
Theoretical yield
  • The maximum mass of product predicted from the balanced equation.
Actual yield
  • Mass of product actually obtained.
Carbon dioxide
  • A gas that turns limewater cloudy.
Solute
  • A substance that dissolves in a solvent.
Hydrogen
  • A gas that gives a squeaky pop with a lighted splint.
Reactants
  • The substances that react together at the start of a reaction.
Oxygen
  • A gas that relights a glowing splint.

Section 8 of 9Key terms

TermMeaning
TitrationAnalytical technique using a solution of known concentration.
AnalyteSolution whose amount is being determined.
TitrantSolution of known concentration added from the burette.
Equivalence pointPoint where moles of titrant equal the stoichiometric amount of analyte.
End pointPoint where the indicator changes colour.
BuretteGlassware delivering variable volumes of titrant.

Section 9 of 9Exam technique

1
Confusing the equivalence point with the end point — one is stoichiometric, the other is a colour change
2
Rinsing the burette with water instead of titrant
3
Using the initial burette reading as the volume delivered
4
Forgetting the mole ratio when the reaction is not 1:1

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