Volumetric Analysis

Question 1

Titration

Answer 1

A procedure used to identify the unknown concentration of a solution by reacting it with a solution of known concentration and measuring the volume of the known solution required for a complete reaction.

Question 2

Aliquot

Answer 2

An accurately known volume of a solution (delivered by a pipette)

Question 3

Titrant

Answer 3

Solution of known concentration and volume (usually in burette)

Question 4

Analyte/titrand

Answer 4

Solution of unknown concentration but known volume (usually from pipette)

Question 5

Titre

Answer 5

Total volume of solution delivered by burette to reach end point of titration

Question 6

Concordant titres

Answer 6

The titre volume of 3 or more titres lie within 0.1mL

Question 7

Equivalence point

Answer 7

Occurs at the pH where the number of OH- ions is equal to the number of H+ ions and the solution only contains salt and water

Question 8

End point

Answer 8

The pH where the indicator changes colour - we want the end point to be as close to the equivalence point as possible

Question 9

Useful formulas

Answer 9

C1V1 = C2V2
C = n/V
n= m/M

Question 10

Buffers

Answer 10

An equilibrium solution that can resist pH change when an acid or base is added
Maintains pH by neutralising small amounts of acids or bases
Buffers have a working pH range in which they can neutralise changes
Made of a weak acid/base and its conjugate salt

Question 11

Buffer example (CH3COOH)

Answer 11

CH3COOH <-> CH3OO- + H+

If acid is added to system, buffer will shift left to reduce H+
If base is added, buffer will shift right to increase H+

Question 12

Choosing an acid/base indicator

Answer 12

Pick an indicator with a pKa the same as (or within range of) the equivalence point of the titration