Chapter 11: Titrations in Analytical Chemistry

Question 1

also called as titrimetric methods

Answer 1

titration methods

Question 2

involve measuring the volume of a solution of known concentration that is needed to react completely with the analyte

Answer 2

volumetric titration

Question 3

the mass of the reagent is measured instead of its volume that is needed to react completely with the analyte

Answer 3

gravimetric titrations

Question 4

the “reagent” is a constant direct electrical current of known magnitude that consumes the analyte.

Answer 4

coulometric titrations

Question 5

are based on determining the quantity of a reagent of known concentration that is required to react completely with the analyte. The reagent may be a standard solution of a chemical or an electric current of known magnitude.

Answer 5

titration methods

Question 6

the quantity of charge required to
complete a reaction with the analyte
is the measured quantity

Answer 6

coulometric titrations

Question 7

is a reagent of known concentration that are used in titrations and in many other chemical analyses or carrying out volumetric titration

Answer 7

standard solution

Question 8

is a process in which the excess of a standard solution used to consume an analyte is determined by titration with a second standard solution. __________ are often required when the rate of reaction between the analyte and reagent is slow or when the standard solution lacks stability.

Answer 8

back-titration

Question 9

other name for standard solution

Answer 9

standard titrant

Question 10

TRUE or FALSE
The volume or mass of reagent needed to complete the titration is determined from the difference between the initial and final readings.

Answer 10

TRUE

Question 11

It is sometimes necessary to add an excess of the standard titrant and then determine the excess amount by ____________ with a second standard titrant

Answer 11

back titration

Question 12

The ________ in a titration is a theoretical point reached when the amount of added titrant is chemically equivalent to the amount of analyte in the sample

Answer 12

equivalence point

Question 13

TRUE or FALSE
We cannot determine the equivalence point of a titration experimentally. Instead, we can only estimate its position by observing some physical change associated with the condition of chemical equivalence, which the position of this change is called

Answer 13

TRUE
endpoint

Question 14

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

Answer 14

titration error

Question 15

are often added to the analyte solution to produce an observable physical change (signaling the end point) at or near the equivalence point

Answer 15

indicator

Question 16

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

Answer 16

equivalence point

Question 17

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

Answer 17

end point

Question 18

formula of tiration error

Answer 18

titration error= actual volume of reagent required - theoretical volume necessaru to reach the equivalence point

Question 19

is an ultrapure compound that serves as the
reference material for a titration or for another type of quantitative analysis

Answer 19

primary standard

Question 20

is a highly purified compound that serves as a reference material in titrations and in other analytical methods

Answer 20

primary standard

Question 21

important requirements for a primary standard are

Answer 21

high purity
atmospheric stability
absence of hydrate water
modest cost
reasonable solubility in the titration medium
reasonable large molar mass so that relative error is minimized

Question 22

is a compound whose purity has been
determined by chemical analysis.
The _____________ serves as the working standard material for titrations and for many other analyses

Answer 22

secondary standard

Question 23

In a ____________, the concentration of a volumetric solution is determined by titrating it
against a carefully measured quantity of a primary or secondary standard or an exactly known volume of another standard solution.

Answer 23

standardization

Question 24

carefully determined mass of a primary standard is dissolved in a suitable solvent and diluted to a known volume in a volumetric flask

Answer 24

direct method

Question 25

the titrant to be standardized is used to titrate (1) a known mass of a primary standard,(2) a known mass of a secondary standard, or (3) a measured volume of another standard solution.

Answer 25

standardization

Question 26

A standardized titrant is sometimes referred to ______, which its conc is also subjected to a larger uncertainty than is the conc of a primary standard solution

Answer 26

secondary-standard solution

Question 27

is the number of equivalents of reagent in the same volume.

Answer 27

normal concentration

Question 28

differ from their volumetric counterparts in that the mass of titrant is measured rather than the volume

Answer 28

mass (weight) or gravimetric titrations

Question 29

most common ways for mass titrations is

Answer 29

weight concentration (mole of solute/kg of solvent)

Question 30

are plots of a concentration-related variable versus titrant volume.

Answer 30

titration curves

Question 31

is a plot of some function of the analyte or titrant concentration on the y-axis versus titrant volume on the x-axis.

Answer 31

titration curve

Question 32

the p-function of analyte (or sometimes the titrant) is plotted as a function of titrant volume

Answer 32

sigmoidal curve

Question 33

measurements are made on both sides of, but well away from, the equivalence point

Answer 33

linear segment curve

Question 34

TRUE or FALSE The sigmoidal type offers the advantages of speed and convenience.

Answer 34

TRUE

Question 35

TRUE or FALSE The linear segment type is advantageous for reactions that are complete only in the presence of a considerable excess of the reagent or analyte.

Answer 35

TRUE

Question 36

Advantages of Gravimetric Titrations

Answer 36

1. calibration of glassware and tedious cleaning ensuring proper drainage is completely eliminated 2. Temperature corrections are unnecessary because the mass (weight) molar concentration does not change with temperature 3. Mass measurements can be made with considerably greater precision and accuracy than can volume measurements. 4. Gravimetric titrations are more easily automated than are volumetric titrations.

Question 37

2 most widely used signals to observe endpoint

Answer 37

(1) changes in color due to the reagent (titrant), the analyte, or an indicator and (2) a change in the potential of an electrode that responds to the titrant concentration or the analyte concentration

Question 38

a titration error in acid-base titrations that occurs when the pH at which the indicator changes color differs from the pH at the equivalence point

Answer 38

determinate error

Question 39

This type of error can usually be minimized by choosing the indicator carefully or by making a blank correction.

Answer 39

determinate error

Question 40

a titration error in acid-base titrations that originates from the limited ability of the human eye to distinguish reproducibly the intermediate color of the indicator

Answer 40

indeterminate error

Question 41

is performed by slowly adding a standard solution from a buret or other liquid-dispensing device to a solution of the analyte until the reaction between the two is judged complete.

Answer 41

titration

Question 42

TRUE or FALSE It is sometimes necessary to add an excess of the standard titrant and then determine the excess amount by back-titration with a second standard titrant

Answer 42

TRUE

Question 43

instruments that can detect end points

Answer 43

calorimeters turbidimeters spectrophotometers temperature monitors refractometers voltmeter current meter conductivity meter

Question 44

TRUE or FALSE purity of such a secondary standard must be established by careful analysis

Answer 44

TRUE

Question 45

ideal standard solution for a titrimetric method should do the following

Answer 45

be sufficiently stable react rapidly with the analyte react more or less completely with the analyte undergo selective reaction with the analyte

Question 46

a titrant that is standardized is sometimes referred to as a

Answer 46

secondary-standard solution

Question 47

TRUE or FALSE The concentration of a secondary-standard solution is subject to a larger uncertainty than is the concentration of a primary-standard solution

Answer 47

TRUE

Question 48

TRUE or FALSE Many reagents lack the properties required for a primary standard and, therefore, require standardization

Answer 48

TRUE

Question 49

standard solutions are normally expressed in

Answer 49

molar concentration normal concentration

Question 50

refersto a balance and a weighable solution dispenser that are substituted for a buret and its markings

Answer 50

mass titration

Question 51

formula of molality

Answer 51

mole of solute/ kg of solution

Question 52

TRUE or FALSE end point is signaled by an observable physical change near the equivalence point of a titration

Answer 52

TRUE