Analytical Chemistry Chapter 6

Question 1

Include a large and powerful group of quantitative procedures based on measuring the amount of a reagent of known concentration (standard solution titrant) that is consumed by an analyte.

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

Answer 1

Titrimetric methods

Titrimetry

Question 2

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

Answer 2

Volumetric Titrimetry

Question 3

It differs only because the mass of the reagent is measured instead of its volume.

Answer 3

Gravimetric Titrimetry

Question 4

The “reagent” is a constant direct electrical current of known magnitude that consumes the analyte; here, the time required to complete the electrochemical reaction is measured.

Answer 4

Coulometric Titrimetry

Question 5

Titrimetric methods are widely used for routine determinations. Why?

Answer 5

🍄Rapid
🍄Convenient
🍄Accurate
🍄Readily automated

Question 6

Used for the determination of naturally occurring and synthetic acids and bases and, in addition, molecular species that can be converted to acids or bases by chemical reaction.

Answer 6

Neutralization titrations

Question 7

Includes a group of analytical methods bașed on determining the quantity of a reagent of known concentration that is required to react completely with the analyte.

The reagent may be a:

Answer 7

Titrimetry

🍒standard solution of a chemical
🍒electric current of known magnitude

Question 8

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

Answer 8

Volumetric Titrimetry

Question 9

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

Answer 9

Coulometric Titrimetry

Question 10

Is a reagent of-known concentration: that is used to carry out a titrimetric analysis.

Answer 10

standard solution (or a standard titrant)

Question 11

A _______ is performed by adding 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 11

titration

Question 12

The volume of a reagent needed to complete the titration is determined from the _______.

Answer 12

Difference between the initial and final volume readings.

Question 13

The ______ in a titration is reached when the amount of added titrant is chemically equivalent to the amount of analyte. in the sample.

Answer 13

equivalence point

Question 14

What is the equivalence point of:

🍦titration of NaCl with AgNO3

🍦titration of H2SO4 with NaOH

Answer 14

🍦1 mol of Ag ion has been added for each mole of chloride ion in the sample.

🍦 2 mol of base for each mole of acid.

Question 15

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

Answer 15

standard solution

Question 16

Is 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 16

Titration

Question 17

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.

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

Answer 17

Back-titration

Question 18

The equivalence point of a titration cannot be determined experimentally. What to do instead?

This change is called:

Answer 18

we can only estimate its position by:

observing physical change associated with the condition of equivalence.

♡end point for the titration

Question 19

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

Answer 19

titration error

Question 20

Are often added to the analyte solution to give an observable physical change (the end point) at or near the equivalence point. We shall see that large changes in the relative concentration of analyte or titrant occur in the equivalence point region. These concentration changes cause the ____ to change the appearance.

Typical indicator changes include the:

Answer 20

Indicators

appearance or disappearance of a color

a change in color

or the appearance or disappearance of turbidity

Question 21

We often use _____ to detect end points. These instruments respond to certain properties of the solution that change in a characteristic way during the titration.

Instruments for detecting end points include:

Answer 21

instruments

colorimeters
turbidimeters
temperature
monitors
voltmeters
current meters
conductivity meters

Question 22

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

Related to the amounts of reactants consumed

Answer 22

equivalence point

Question 23

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

Answer 23

end point

Question 24

In volumetric methods; the titration error Et is given by:

Et

Veq

Vep

Answer 24

Et = Vep - Veq

Where Veq is the theoretical volume of reagent required to reach the equivalence point

and Vep is the actual volume used to arrive at the end point

Question 25

In volumetric methods; the titration error Et is given by:

Answer 25

where Veq is the theoretical volume of reagent required to reach the equivalence point, and Vep.is the actual volume-used to arrive at the end. point.

Question 26

A ________ is a highly purified compound that serves as a reference material in all volumetric and mass titrimetric methods.

The accuracy of a method is critically dependent on the properties of this compound. Important requirements for a primary standard are:

Answer 26

primary standard

High purity
Atmospheric stability
Absence of hydrate water (so that the composition of the solid does not change with variations in relative humidity)
Ready availability at modest cost
Reasonable solubility in the titration medium
Reasonably large molar mass so that the relative error associated with weighing the standard is minimized.

Question 27

A _______ is an ultapure compound that serves as the reference material for the titrimetric method of analysis.

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

Answer 27

primary standard

secondary standard

Question 28

The ideal standard solution for a titrimetric method will:

Answer 28

1. Be sufficiently stable so that it is only necessary to determine its concentration once
2. React rapidly with the analyte so that the time required between additions of reagent ıs minimized
3. React completely with the analyte so that satisfactory end points are realized
4. Undergo a selective reaction with the analyte that can be described by a balanced equation.

Question 29

The accuracy of a titrimetric method can be no better than the accuracy of the concentration of the standard solution used in the titration.

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

Answer 29

Direct method
Standardization

Question 30

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

The titrant to be, standardized is used to titrate:

Answer 30

Direct method

Standardization

(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

Question 31

A titrant that is standardized against a secondary standard or against another standard solution is sometimes referred to as a ________.

Answer 31

secondary standard solution

Question 32

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 accurately known volume of another standard solution.

Answer 32

standardization

Question 33

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

The first gives the _____ contained in one liter of solution (no. mol analyte present mol standard reagent added),

and the second gives the _____ in the same volume. (no. eq analyte- present: = no.eq standard reagent added).

Answer 33

molarity c or normality cN.

number of moles of reagent

number of equivalents of reagen

Question 34

Is the normality of a solution can never be specified without knowledge about how the solution will be used?

One equivalent weight of a substance paricipating in a neutralization reaction is that amount of substance (molecule, ion, or paired ion such as NaOH) that either reacts with or supplies 1 mol of hydrogen ions in that reaction.

Answer 34

Yes

Question 35

Most _____ are based on two pairs of fundamental equations that are derived from definitions of millimole, mole, and molar concentration.

Answer 35

volumetric calculations

Question 36

The law of conservation of mass states that _____.

Equation 6-2 is simplified as:

C1V1= C2V2
Where C1’s and V1’s are concentrations and volumes before and after change.

Other forms of expression,

M1V1 = M2V2=

N1V1=N2V2

C1V1 = C2V2

Answer 36

mass remains constant in chemical change

🍭mass (in mols or no. meq) remains constant before and after change.

🍭amount (in mols) = mass/molar mass or mass/MW

🍭amount (in no. eq) = mass/eqw for normality calculation

🍭for percentage calculation.

Question 37

Two types of volumetric calculations

The first involves computing the___

The second involves _____.

Both types are based on three algebraic relationships:

Answer 37

1️⃣molarity of solutions that have been standardized against either a primary standard or another standard solution.

2️⃣calculating the amount of analyte in a sample from titration data.

⚪️⚪️⚪️
Two of these are Equations 6-2 and 6-4, which are based on millimoles and milliliters.

The third relationship is the stoichiometric ratio of the
number of millimoles of the analyte-to the number of millimoles of titrant.

Question 38

Basic principle
aA +bB -> Products
A:
B:
a and b are the:

Answer 38

Titrant (standard solution)
Analyte (unknown )
number of moles of each

Question 39

Requirments inTitration

Answer 39

1-stoichiometric reaction
2- rapid rate reaction 3- quantitative reaction (99.9%complete at stoichiometry) 4-have a defined end or equivalence point

Question 40

Related to the amounts of reactants consumed.

Related to the physical sign that is associated with the condition of chemical equivalence.

Ideally, the _____ one coincide. (variation may be to _____)

Answer 40

Equivalence point

End point

end point and equivalent point

color change of indicator

Question 41

Standard Solution

A process in which concentration of a volumetric solution is determined by titrating it with a known mass of a primary standard.

Answer 41

A primary standard
A secondary standard

Standardization

Question 42

This is performed by adding a standard solution from a buret or other liquid- dispensing device to a solution of the analyte until the point at which the reaction is believed to be complete.

Answer 42

Titration

Question 43

PRIMARY STANDARD

Answer 43

• HIGH PURITY
• ATMOSPHERIC STABILITY
• INDEPENDENT OF HUMIDITY
• MODEST COST
• LARGE MOLAR MASS
• NON HGYROSCOPIC

Question 44

Types of titrimetry

1- Precipitation:

2- Acid Base titration:

3- Complex formation

4- Oxidation Reduction

Answer 44

1. (Ag+) + (CI-) -> AgCI (s)
2. (OH-) + (HA) -> (A-) +H2O
3. (EDTA2-) + (Ca2+) -> EDTA Ca.xH20
4. (MnO4-) + (5Fe2+) + (8H+) -> (5Fe3+) + (Mn2+) + (4H20)

Question 45

Calculations with Molarity

Is the formula weight of a substance expressed in grams

Number of moles =
Number of m.moles =
Molarity=

Answer 45

The mole

weight in grams/formula weight

weight in milligrams/formula weight

Moles/Liter or mmoles/ml

Question 46

Moles=
Weight (g) =
m.Moles=
Weight (mg) =

Answer 46

Volume (L). (M)

Volume (L). (M). form weight (g)

Volume (ml). (M)

Volume (ml). (M) . form weight (g)