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Pharm Ana 1 LEC > [Prelim] Titrimetry > Flashcards

[Prelim] Titrimetry Flashcards

1
Q

A.k.a. as Volumetric Analysis

A

TITRIMETRIC ANALYSIS

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2
Q

● Analytical method in which the volume of a
solution of known concentration consumed
during an analysis is taken as a measure of the
amount of active constituent in a sample being
analyzed

A

PRINCIPLES OF TITRIMETRIC ANALYSIS

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2
Q

Chemical substances being analyzed

A

ANALYTE OR ACTIVE CONSTITUENTS

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2
Q

A chemical which changes color at or
very near the point in the titration where
equivalent quantities of analyte and
titrant have reacted

A

INDICATOR

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3
Q

Solution of known concentration usually
added by means of a buret

A

TITRANT

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4
Q

The act of adding and measuring the
volume of titrant used in the assay

A

TITRATION

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5
Q

Theoretical point at which equivalent
amounts of a titrant and analyte have
reacted

A

STOICHIOMETRIC POINT OR EQUIVALENCE
POINT

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6
Q

Titration is actually stop at some point at
which there occurs a sudden change in
some property of the reaction mixture

A

END POINT

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7
Q

Weight in grams which is chemically
equivalent to 1 gram-atom of hydrogen
(1.0079 g)

A

GRAM-EQUIVALENT WEIGHT (GEW) or
gram-equivalent of a chemical

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8
Q

The number of gram-equivalents
involved in a quantitative procedure

A

EQUIVALENT (EQUIV)

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9
Q

In neutralization reactions it is defined
as that weight of a substance in grams
which (1) contains, (2) furnishes, (3)
reacts with direct or indirectly, or (4)
replaces as gram-atom or ion of
hydrogen

A

GRAM-EQUIVALENT WEIGHT (GEW) or
gram-equivalent of a chemical

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10
Q

GEW/1000

A

GRAM-MILLIEQUIVALENT WEIGHT (GmEW)

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11
Q

The number of gram-mill equivalents
involved in a quantitative procedure

A

MILLIEQUIVALENT (MEQ)

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12
Q

Solution of known normality or molarity

A

STANDARD SOLUTION

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13
Q

The number of equivalents of solute per
liter (equiv/liter) or milliequivalent per
milliliter (meq/ml) of a solution

A

NORMALITY

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14
Q

Expression of the concentration of a
solution in terms of moles per liter

A

MOLARITY

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15
Q

Determination of the normality or
molarity of a solution

A

STANDARDIZATION

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16
Q

The use of carefully weighed sample of
a substance of known purity

A

PRIMARY STANDARD

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17
Q

The use of another standard solution.

A

SECONDARY STANDARD

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18
Q

Weight of a substance chemically
equivalent to 1ml of a standard solution

A

TITER

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19
Q

INDICATORS used

A

○ to determine the end point in
neutralization processed
○ to determine hydrogen-ion
concentrations pH, or
○ to indicate that a desired change in pH
has been affected

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19
Q

TYPES OF CHEMICAL REACTIONS USED
IN TITRIMETRY

A

● Neutralization
● Redox
● Precipitation
● Complexation
● Diazotization

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19
Q

Used to sharpen up the color change

A

MIXED INDICATORS

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19
Q

REQUIREMENTS for CHEMICAL REACTIONS USED IN TITRIMETRY

A

● Reaction must proceed to completion (k = 108)
● Reaction must proceed in a stoichiometric
manner
● Suitable end-point-detecting device must be
available
● Direct titrimetric methods - the reaction must be rapid so as end point is discernible

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19
Q

TYPES OF VOLUMETRIC APPARATUS

A

● t.d
● t.c
● A warm cleaning solution (sod. dichromate in sulfuric acid), a solution of trisodium phosphate or a solution of synthetic detergent – best cleaning agent to use

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19
Q

the reaction must be rapid so as end point is discernible

A

Direct titrimetric methods

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20
Q

TITRIMETRIC ANALYSIS BASED ON
NEUTRALIZATION REACTION

A
  • INDICATORS
  • MIXED INDICATORS
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20
Q

Complex organic compounds used

A

INDICATORS

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21
Q

THEORIES TO EXPLAIN THE COLOR
CHANGE OF INDICATORS

A
  • PHYSIOCHEMICAL
  • ORGANIC THEORY
  • COLLOIDAL
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22
Q

Attributes the color of certain ions, an increase
in which causes the appearance of a new color, a decrease in which causes the disappearance of a color or appearance of a diff color

A

PHYSIOCHEMICAL

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22
Q

Attributes the color of indicator to certain
groupings of the elements in a compound and
the change in color to a change in molecular
structure

A

ORGANIC THEORY

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23
Q

Assumes that indicator form colloidal solutions the change in color of which is dependent upon change in size of the colloidal particle

A

COLLOIDAL

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23
Q

● Use 3 drops of indicator test solution for a
titration unless otherwise directed
● When a strong acid is titrated with a strong
alkali, or a strong alkali with a strong acid,
methyl orange, methyl red, or phenolphthalein
may be used
● When a weak acid is titrated with a strong alkali, use phenolphthalein as the indicator
● When a weak alkali is titrated with a strong acid, use methyl red as the indicator
● A weak alkali should never be titrated with a
weak acid, or vice versa, since no indicator will
give a sharp end point
● The appearance of a color is more easily
observable than is the disappearance
○ Therefore, always titrate where possible
to the appearance of a color

A

RULES OF USE OF INDICATORS

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23
Q

Commonly Used pH Indicators

A
  • Methyl Red
  • Phenolphthalein
  • Malachite Green
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24
Q

Methyl Red

A
  • pH range: 4.2- 6.2
  • Acid: Red
  • Base: Yellow
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24
Q

Malachite Green

A
  • pH range: 0-2
  • Acid: Yellow
  • Base: Green
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25
Q

Phenolphthalein

A
  • pH Range: 8-10
  • Acid: Colorless
  • Base: Red
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26
Q

Methyl Orange

A
  • Acid: Pink
  • Base: Red
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27
Q

Methyl Yellow

A
  • Acid: Red
  • Base: Red
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28
Q

Methyl Red

A
  • Acid: Red
  • Base: Red
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29
Q

Phenolphthalein

A
  • Acid: Colorless
  • Base: Red
30
Q

Malachite Green

A
  • Acid: Yellow
  • Base: Green
31
Q

Bromothymol Blue

A
  • Acid: Yellow
  • Base: Blue
32
Q

Phenol Red

A
  • Acid: Yellow
  • Base: Red
32
Q

Cresol Red

A
  • Acid: Yellow
  • Base: Red
32
Q

Thymol Blue

A
  • Acid: Yellow
  • Base: Blue
33
Q

Bromocresol Green

A
  • Acid: Yellow
  • Base: Blue
34
Q

Acidimetry uses a standard acid solution in a burette to titrate a known volume of base in a conical flask.

A

ACIDIMETRIC ANALYSIS

35
Q

2 types of ACIDIMETRIC ANALYSIS

A
  • DIRECT TITRATION
  • RESIDUAL TITRATION
36
Q

A.k.a. BACK TITRATION

A

RESIDUAL TITRATION

36
Q

Used when ever the end point of a direct titration
deviates appreciably from the stoichiometric
points for some reason; e.g, when the basic
sample is insoluble in water and rate of its
reaction with the standard acid is relatively slow

A

RESIDUAL TITRATION

36
Q

Conducted by introducing a standard acid
solution gradually from a burette into a solution of the base being assayed until chemically equivalent amounts of each have reacted as shown by some change in properties of the mixture

A

DIRECT TITRATION

37
Q

When the substance to be assayed does not
give a distinct, sharp end point with an indicator by direct titration

A

RESIDUAL TITRATION

38
Q

ASSAY OF SODIUM BICARBONATE - DIRECT
TITRATION

A
  • METHYL ORANGE
39
Q

A macro method in which the ammonia is
distilled into excess boric acid solution.

A

METHOD I

39
Q

ASSAY OF ZINC OXIDE - RESIDUAL
TITRATION

A

● Freshly ignited zinc oxide, contains nlt 99% and nmt 100.5% of ZnO
● Methyl orange – indicator
● Titrant – 1N H2SO4 and 1N NaOH
● The equivalent weight is 40.68g, therefore each mL of 1N H2SO4
○ 1 mEq neutralized by ZnO is equivalent
to 40.68 mg

39
Q

Used as indicator because
phenolphthalein and most other
indicators are affected by the carbonic
acid liberated in the reaction, which
causes a change in color before the
reaction is complete

A

METHYL ORANGE

40
Q

NITROGEN DETERMINATION BY KJELDAHL
METHOD

A
  • METHOD I
  • METHOD II
40
Q

ASSAY OF MILK OF MAGNESIA - RESIDUAL
TITRATION

A

● Methyl red – indicator used
● U.S.P. requires that milk of magnesia contain not less than 7% and not more than 8.5% Mg(OH)2
● Milk of magnesia is dissolved in accurately
measured excess of 1N sulfuric acid solution to ensure complete neutralization of all the
magnesium hydroxide with the formation of the soluble magnesium sulfate

41
Q

It is used if nitrates or nitrites are not present

A

METHOD I

42
Q

One gram of sample is used

A

METHOD I

42
Q

A semi micromethod in which smaller samples
are employed using a semi micro Kjeldahl
apparatus

A

METHOD II

43
Q

2-3 milligram of sample is used

A

METHOD II

44
Q

Titrant; acid
Analyte; base

A

ACIDIMETRIC ANALYSIS

44
Q

Nitrogen is first liberated by acid digestion

A

METHOD II

45
Q

Titrant; base
Analyte; acid

A

ALKALIMETRIC ANALYSIS

45
Q

● Titrant used is base and the analyte used is
acid
● Methyl red and phenolphthalein – can be
used as indicators in most inorganic acids
● Phenolphthalein – frequently used indicator in organic acids
● Thymol blue, bromothymol blue and
thymolphthalein – also employed as indicator
in organic acids

A

ALKALIMETRIC ANALYSIS

46
Q

Phenolphthalein

A

frequently used indicator in organic acids

46
Q

can be used as indicators in most in organic acids

A

Methyl red and phenolphthalein

47
Q

also employed as indicator in organic acids

A

Thymol blue, bromothymol blue and
thymolphthalein

48
Q

DIRECT TITRATION METHODS

A

Assay of Hydrochloric Acid

48
Q

Official requirement for concentrated
HC

A

36.5% - 38%

49
Q

Official requirement for diluted HCl

A

9.5g – 10.5g/100 mL

49
Q

RESIDUAL TITRATION METHOD

A

BLANK DETERMINATION

50
Q

○ Without analyte, needed to lessen
titration error
○ Reacts too slowly with the titrant
because of poor solubility

A

BLANK DETERMINATION

51
Q

Official requirement of ASSAY OF ASPIRIN is

A

99.5% - 100.5%

52
Q

REACTION of Alkalimetric Analysis

A

● Neutralization of the free acid by hydrolysis of ASA
● Neutralization of the carboxyl group of the ASA
● Saponification of sodium acetyl salicylate
● Methylparaben (MP) is used in pharmacy as a preservative in pharmaceutical preparations
● Place in a flask about 2g of MP, accurately
weighed, add 40ml of 1N NaOH cover with a
watch glass and boil gently for 1 hour
● Experimental Data

52
Q

Titrated with NaOH to neutralize any free acid
formed by hydrolysis of the acetylsalicylic acid

A

ASSAY OF ASPIRIN

53
Q

used in pharmacy as a preservative in pharmaceutical preparations

A

Methylparaben (MP)

54
Q

Milliliters of 1.100N sulfuric acid required
for blank titration

A

41.00

55
Q

Moisture content should be held to less than
0.05% so as not to have any appreciable effect
on the end point

A

NON-AQUEOUS TITRIMETRIC ANALYSIS

55
Q

Used when the substance to be assayed is
poorly soluble in water

A

NON-AQUEOUS TITRIMETRIC ANALYSIS

55
Q

Milliliters of 1.100N sulfuric acid required
for sample titration

A

31.00

56
Q

The disadvantage of poor solubility and weak
reactivity with water were overcome
● Simplicity, speed, precision, and accuracy are equivalent to those of the classical procedures

A

ADVANTAGES of ALKALIMETRIC ANALYSIS

57
Q

● Moisture is to be avoided, since H2O, being
weakly basic, would compete with the weak nitrogen base for the HClO4 and the sharpness of the end point would be lost
● Greater care in the control of temperature during the standardization, and analysis procedures is necessary

A

DISADVANTAGES of ALKALIMETRIC ANALYSIS

58
Q

Such as acetonitrite, alcohols,
chloroform, benzene, dioxane,
or ethyl acetate are either
aprotic or amphiprotic in nature
and are used for their solvency
action primarily, since they do
not enhance dissociation to any
great degree

A

Neutral solvents

58
Q

Titrant; acid
analyte; base

A

SOLVENTS in ACIDIMETRY IN NON-AQUEOUS
SOLVENTS

59
Q

Either relatively neutral or acidic
in nature

A

SOLVENTS used

60
Q

Such as formic, glacial acetic
acid, and propionic acids, acetic
anhydride, and sulfonyl chloride,
are used for weak bases and
their salts where the protogenic
quality of the solvent is utilized

A

Acidic solvents

60
Q

Weakly basic substances (e.g. amines, amine
salts, heterocyclic nitrogen compounds, alkali
salt of organic acid, alkali salts of weak in
organic acids, and amino acids)

A

SAMPLE of ACIDIMETRY IN NON-AQUEOUS
SOLVENTS

61
Q

Perchloric acid in glacial acetic acid or the
relatively neutral solvent dioxane

A

TITRANT

61
Q

The strongest of the known common
acids which gives excellent results with
practically all the known weak bases

A

Perchloric acid

62
Q

Most valuable and widely used titrant

A

Perchloric acid

63
Q

Hydrogen bromide and certain organic sulfuric
acids

A

TITRANT

64
Q

INDICATORS WHICH CAN BE USED IN
THE TITRATION OF RELATIVELY
STRONGER BASES

A

● Methyl red
● Methyl orange
● Thymol blue

64
Q

Indicators which can be used in the titration of
weak bases and their salts

A

○ Crystal violet
○ Methylrosaniline chloride
○ Quinaldine red
○ Alpha-naphtholbenzein
○ Malachite green

65
Q

Titrant; base
analyte; acid

A

ALKALIMETRIC IN NON-AQUEOUS
SOLVENT

66
Q

Strong bases which can be used as solvents for the titration of weak acids such as enols

A

○ Ethylenediamine
○ n-butylamine
○ morpholine

67
Q

Weaker base solvents which can be used as
solvents for medium-strength acidic substances

A

○ Dimethylformamide
○ Pyridine

68
Q

In the titration of acidic compounds the bases
that are used officially are __________ &________

A

sodium methoxide and
lithium methoxide

68
Q

SAMPLE of ALKALIMETRIC IN NON-AQUEOUS
SOLVENT

A

● Acid halides
● Anhydrides
● Acids
● Amino Acids
● Enols such as barbiturates and xanthines
● Imides
● pyrroles
● Sulfonamides
● Organic salts of inorganic acids
● Phenols

Pharm Ana 1 LEC (3 decks)

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