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QC > chap 7 > Flashcards

chap 7 Flashcards

1
Q

require the formation of relatively insoluble substances or precipitates to cause the reactions to go to completion; solution must be titrated

A

Volumetric Precipitimetry

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2
Q

Cessation of precipitation or the appearance of turbidity
-Use of internal indicators
-Instrumental methods
(i.e. potentiometric or amperometric)

A

Determination of End point

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3
Q

used in both direct and residual titration

a. employs standard ammonium thiocyanate solution
b. thiocyanate reacts with Hg or Ag ions present to form white precipitate of
silver or mercuric thiocyanate

A

Ferric Ammonium Sulfate (FAS/Ferric Alum)

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4
Q

reacts with Hg or Ag ions present to form white precipitate of
silver or mercuric thiocyanate

A

thiocyanate

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5
Q

reacts with ferric ammonium sulfate to form a red ferric thiocyanate
the first appearance of of the red color makes the end point of the reaction

A

thiocyanate ions

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6
Q

AgNO3 + NH4SCN –>

A

AgSCN + NH4NO3 (white)

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7
Q

FeNH4(SO4)2 + 3 NH4SCN –>

A

FeSCN + 2 (NH4)2SO4 (RED)

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8
Q

forms a red precipitate of silver chromate which is seen against the background of white silver chloride

A

Potassium Chromate TS

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9
Q

AgNO3 + NaCl

A

AgCl+NaNO3

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10
Q

2 AgNO3 + K2CrO4

A

AgCro4+2KNO3 (Red)

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11
Q

used in the analyses of halides by direct
titration with silver nitrate solution a. Dichlorofluorescein (DCF) TS
b. Eosin Y TS
c. Tetrabromophenolphthalein Ethyl
Ester (TEE) TS

A

Adsorption Indicators

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12
Q

0.1 N Silver Nitrate
0.1 N Ammonium Thiocyanate

A

Standard solutions

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13
Q

named after Karl Friedrich Mohr
a. for determining chloride content
b. the chloride is titrated with AgNO3 solution
c. soluble chromate (K2CrO4) is added as indicator

A

MOHR method

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14
Q

This method is useful for determining chloride in drinking water.

2 Ag+(aq) + CrO42-(aq) YELLOW SOLUTION–>

A

Ag2CrO4(s) RED PPT

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15
Q
  • indirect or back titration procedure
  • for determination of anions that
    precipitate silver like Cl-, Br-, I-,
    SCN-
  • a measured excess of AgNO3
    solution is added to precipitate the anion
A

VOLHARD METHOD

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16
Q

the excess in back titration is titrated with standard NH4SCN
- uses ferric ammonium sulfate as indicator
- named after Jacob Volhard

A

VOLHARD METHOD

17
Q

added to form a film over the precipitated AgCl

A

NITROBENZENE

18
Q

makes use of adsorption indicators
- typically DCF for Cl-
- he endpoint is marked by
green suspension turning to pink

A

FAJANS METHOD

19
Q

is suitable for titrating against Br-, I-, SCN-

A

EOSIN

20
Q

type of titration involving silver ions

-used to determine Cl- in a sample
-sample is titrated against a solution of AgNO3

A

Argentometry

21
Q

precipitate organic nitrogen compounds such as alkaloids, amines
- also used for ammonium, K and Ag ions
- uses chloroform as extraction indicator

A

Sodium Tetraphenylboron Titrations

22
Q

precipitate organic nitrogen compounds such as alkaloids, amines
- also used for ammonium, K and Ag ions
- uses chloroform as extraction indicator

A

SODIUM TETRAPHENYLBORON TITRATIONS

23
Q

for metal determination using EDTA
(ethylenediamine tetraaceta -te)

A

COMPLEXATION METHOD

24
Q

when a metal ion combines with a molecule which can
donate electrons

A

COMPLEX

25
Q

combining molecule contains two or more groups that don -ate electrons

A

CHELATE

26
Q

will react with metal ions to form a water soluble, stable complex or chelate compound

A

EDTA

27
Q

4 oxygen and 2 nitrogen atoms of EDTA make

A

HEXADENTATE molecule

28
Q

more preferred
over the free acid because it is more water soluble, nonhygroscopic and very stable

A

EDTA (disodium salt)

29
Q

determination of metal in the presence of another metal
- Zn will not interfere with Ca titrations at a pH of 13

A

MASKING

30
Q

Potassium Cyanide - Co, Ni, Cu, Zn l Ammonium Fluoride - Ca, Mg, Al to
allow titration of Zn
-Triethanolamine - suppress Al-EDTA
complex
-Thioglycol - inactivate Hg, Cu for titrati- on of Zn
-Ascorbic Acid

A

MASKING AGENTS

31
Q

Co, Ni, Cu, Zn

A

POTASSIUM CYANIDE

32
Q

Ca, Mg, Al to
allow titration of Zn

A

AMMONIUM FLUORIDE

33
Q

suppress Al-EDTA
complex

A

Triethanolamine

34
Q

inactivate Hg, Cu for titrati- on of Zn

A

THIOGLYCOL

35
Q

for Ca, Mg and Zn
- Titrant: Mercuric nitrate
- Indicators: Hydroxynaphthol blue , eriochrome black, xylenol oran ge

A

DIRECT TITRATION

36
Q

for Al and Bi compounds, Mn
- Titrant: Zinc sulfate
- Indicators: dithizone, eriochro- me black T

A

RESIDUAL TITRATIONS

QC (4 decks)

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