Volumetric Precipitation Flashcards

1
Q

Volumetric Precipitation/Precipitimetry

A

Argentometric Method

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2
Q

Formation of INSOLUBLE SUBSTANCES or PRECIPITATES

A

Volumetric precipitation/Argentometric Method

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3
Q

Methods for determination of Endpoint

A
  1. Turbidity Method
    a. Cessation of Precipitation - Gay Lussac
    b. Appearance of Turbidity - Liebig
  2. Use of Internal Indicators
    a. Mohr
    b. Volhard
    c. Fajans
  3. Instrumental Methods
    a. Potentiometry
    b. Amperometric
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4
Q

Gay-Lussac’s Method

A

Direct Titration

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5
Q

Standard in Gay-Lussac Method

A

NaCl

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6
Q

Indicator in Gay-Lussac’s Method

A

None

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7
Q

Gay-Lussac Method Assay

A

Ag with Cl

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8
Q

Volumetric Soln or Titrant in Volumetric precipitation

A

AgNO3 (Silver nitrate)

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9
Q

Standard in Liebig Method

A

NaCl

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10
Q

Indicator in Liebig Method

A

None

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11
Q

Assay of Liebig Method

A

Cyanide

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12
Q

Standard in Modified Liebig (Denige’s)

A

Aq. Ammonia

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13
Q

Indicator in Modified Liebig (Denige’s)

A

KI T.S

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14
Q

Endpoint in Modified Liebig (Denige’s)

A

SIlver Iodide - Yellow ppt

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15
Q

Volhard Precipitation

A

Residual Titration

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16
Q

Standard in Volhard Method

A

Silver Nitrate
Ammonium thiocyanate

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17
Q

Indicator in Volhard Method

A

Ferric Ammonium Sulfate/Ferric Alum

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18
Q

Endpoint in Volhard Method

A

Red color (Ferric thiocyanate)

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19
Q

Assay of Volhard Method

A

NaCl

20
Q

Standard in Volhard Method

A

NaCl, Dil. HCl
Silver Nitrate

21
Q

Ammonium thiocyanate VS is a _______, so slight amount in excess of theoretical quantityt required is used in prep of the solution

A

Deliquescent

22
Q

Can be used as an alternative to Ammonium thiocyanate as VS in Volhard Precipitation method

A

Potassium thiocyanate

23
Q

Endpoint of Liebig Method

A

Turbidity - Ag[Ag(CN)2] ppt

24
Q

Use of Nitric Acid in Volhard Method

A

Prevent precipitation of Silver as Carbonate and Phosphate
Prevent hydrolysis of Ferric Alum

25
Q

Advantages of using Nitric Oxide in Volhard

A

Strongly acidic environment
Don’t interfer with other ions such as carbonate, oxalate, arsenate

26
Q

Application of Volhard Method

A

Determination of Halide ions
Determination of purity of soluble chlorides or ionic halogens

27
Q

% purity formula for volhard method

A

% Purity = ((N x V) Ag - (N x V) NH4SCN) x 0.05844 / wt sx * 100

28
Q

Mohr Method

A

Direct Titration

29
Q

Mohr Method is used for determination of

A

Cl, Br, CN
Neutral and buffered solutions such as drinking water

30
Q

Indicator used in Mohr Method

A

Potassium chromate ⭐

31
Q

Standard used in Mohr Method

A

NaCl, Dil HCl

32
Q

Endpoint of Mohr Method

A

Brick-red ppt (Silver chromate)

33
Q

Mohr Method is used for assay of

A

NaCl in Na Lauryl sulfate
Halides

34
Q

Standard used in Fajan’s Method

A

NaCl

35
Q

Indicator used in Fajan’s method

A

Adsorption Indicator
EOSIN Y, DCF, Tetrabromophenolphthalein ethyl ester

36
Q

Fajan’s is used for assay of

A

Halides
Iopanoic acid tablets - Contains iodine and is useful as a contrast medium in cholecystography
Benzyltrimethylammonium chloride

37
Q

Endpoint of Fajan’s

A

Abrupt change in color halide ppt
Pink (?)

38
Q

Fajan’s Indicator

A

Adsorption Indicators

39
Q

Most commonly used indicator

A

Dicholofluoroscein (DCF)

40
Q

Endpoint of Fajan’s if DCF is used

A

Pink

41
Q

Indicator that is useful in the titration of Br, I, and SCN

A

Eosin Y (Tetrabromofluorescein)

42
Q

Endpoint of Fajan’s if Eosin Y is used

A

Pink

43
Q

TF: Eosin Y gives sharper endpoint than DCF and more sensitive

A

True

44
Q

TF: Eosin Y cannot be used for AgCl because it is strongly bound to AgCl than Cl

A

True

45
Q

Endpoint of Fajan’s if Tetrabromophenolphthalein ethylester

A

Green precipitation