Titrations Taking Advantage of Stoichiometric Reactions

Question 1

Analytical Strategy Flow Chart for Titrimetric Analysis

Answer 1

1. Obtain the sample
2. Prepare the sample
3. Carry out the analysis method
4. Work the data
5. Calculate and report results

Question 2

includes a group of analytical methods based on determining the quantity of a reagent of known _____ that is required to react completely with the analyte.

Answer 2

Titrimetry
Concentration

Question 3

a type of titrimetry in which the standard reagent is measured volumetrically.

Answer 3

Volumetric titrimetry

Question 4

a type of titrimetry in which the quantity of charge in coulombs required to complete a reaction with the analyte is measured.

Answer 4

Coulometric titrimetry

Question 5

a reagent of known concentration that is used in a titrimetric analysis.

Answer 5

standard solution

Question 6

a process in which a standard reagent is added to a solution of an analyte until the reaction between the analyte and reagent is judged to be complete.

Answer 6

Titration

Question 7

a process in which the excess of a standard solution used to consume an analyte is determined by titration with a second standard solution.

Answer 7

Back-titration

Question 8

often required when the rate of reaction between the analyte and reagent is slow or when the standard solution lacks stability.

Answer 8

Back-titrations

Question 9

a titration cannot be determined experimentally.

Answer 9

equivalence point

Question 10

the point in a titration when the amount of added standard reagent is equivalent to the amount of analyte.

Answer 10

equivalence point

Question 11

The difference in volume or mass between the equivalence point and the end point is the _________

Answer 11

titration error

Question 12

often added to the analyte solution to give an observable physical change (the end point) at or near the equivalence point.

Answer 12

Indicators

Question 13

the point in a titration when a physical change occurs that is associated with the condition of chemical equivalence.

Answer 13

end point

Question 14

The top surface of a liquid confined in a narrow tube exhibits a marked curvature, or ______

Answer 14

meniscus

Question 15

It is common practice to use the bottom of the meniscus as the point of reference in calibrating and using _____

Answer 15

volumetric equipment.

Question 16

This minimum can be established more exactly by holding an ______ or piece of paper behind the graduations.

Answer 16

opaque card

Question 17

above a line perpendicular to the buret

Answer 17

2.58 mL

Question 18

along a line perpendicular to the buret

Answer 18

12.62 mL

Question 19

below a line perpendicular to the buret

Answer 19

12.67 mL

Question 20

Right-handed persons must use their _____ in swirling the flask and _______in controlling the stopcock.

Answer 20

right hand
left hand

Question 21

Ensure that the tip of the _____is well within the titration flask.

Answer 21

buret

Question 22

The titrant is introduced in increments of about _____ mL.
Constant swirling is necessary to ensure thorough mixing.

Answer 22

one

Question 23

As the titration progresses, the size of the increments must be _____. Dropwise addition is done as the titration reaches the endpoint.

Answer 23

decreased

Question 24

Allow for drainage for at least __ s before recording the final volume reading.

Answer 24

30

Question 25

________ are never used as storage containers. Do not store any solution in a volumetric flask.

Answer 25

Volumetric flasks

Question 26

are not suitable for storing NaOH or other basic solutions. Instead, use plastic containers.

Answer 26

Glass containe

Question 27

a highly purified compound (ultrapure compound) that serves as a reference material in titrations and in other analytical methods.

Answer 27

primary standard

Question 28

primary standard: An example is ________ that is used to measure the concentration of NaOH solutions.

Answer 28

potassium hydrogen phthalate (KHP)

Question 29

Important requirements for a primary standard are the following:

Answer 29

1. high purity
2. atmospheric stability;
3. absence of hydrate water so that the composition of the solid does not change with variations in relative humidity;
4. modest cost
5. reasonable solubility in the titration medium;
6. reasonably large molar mass so that the relative error associated with weighing the standard is minimized.

Question 30

a compound whose purity has been established by chemical analysis and that serves as the reference material for a titrimetric method of analysis

Answer 30

secondary standard

Question 31

Two basic methods are used to establish the concentration of such solutions.

Answer 31

1. direct method
2. standardization

Question 32

which a carefully weighed quantity of a primary standard is dissolved in a suitable solvent and diluted to a known volume in a volumetric flask.

Answer 32

direct method

Question 33

which the titrant to be standardized is used to titrate:

1) a weighed quantity of a primary standard;
2) a weighed quantity of a secondary standard; or
3) a measured volume of another standard solution.

Answer 33

standardization

Question 34

The concentrations of standard solutions are generally expressed in units of either

Answer 34

molarity c or normality cN .