chap 7

Question 1

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

Answer 1

Volumetric Precipitimetry

Question 2

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

Answer 2

Determination of End point

Question 3

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

Answer 3

Ferric Ammonium Sulfate (FAS/Ferric Alum)

Question 4

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

Answer 4

thiocyanate

Question 5

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

Answer 5

thiocyanate ions

Question 6

AgNO3 + NH4SCN –>

Answer 6

AgSCN + NH4NO3 (white)

Question 7

FeNH4(SO4)2 + 3 NH4SCN –>

Answer 7

FeSCN + 2 (NH4)2SO4 (RED)

Question 8

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

Answer 8

Potassium Chromate TS

Question 9

AgNO3 + NaCl

Answer 9

AgCl+NaNO3

Question 10

2 AgNO3 + K2CrO4

Answer 10

AgCro4+2KNO3 (Red)

Question 11

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

Answer 11

Adsorption Indicators

Question 12

0.1 N Silver Nitrate
0.1 N Ammonium Thiocyanate

Answer 12

Standard solutions

Question 13

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

Answer 13

MOHR method

Question 14

This method is useful for determining chloride in drinking water.

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

Answer 14

Ag2CrO4(s) RED PPT

Question 15

• 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

Answer 15

VOLHARD METHOD

Question 16

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

Answer 16

VOLHARD METHOD

Question 17

added to form a film over the precipitated AgCl

Answer 17

NITROBENZENE

Question 18

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

Answer 18

FAJANS METHOD

Question 19

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

Answer 19

EOSIN

Question 20

type of titration involving silver ions

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

Answer 20

Argentometry

Question 21

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

Answer 21

Sodium Tetraphenylboron Titrations

Question 22

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

Answer 22

SODIUM TETRAPHENYLBORON TITRATIONS

Question 23

for metal determination using EDTA
(ethylenediamine tetraaceta -te)

Answer 23

COMPLEXATION METHOD

Question 24

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

Answer 24

COMPLEX

Question 25

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

Answer 25

CHELATE

Question 26

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

Answer 26

EDTA

Question 27

4 oxygen and 2 nitrogen atoms of EDTA make

Answer 27

HEXADENTATE molecule

Question 28

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

Answer 28

EDTA (disodium salt)

Question 29

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

Answer 29

MASKING

Question 30

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

Answer 30

MASKING AGENTS

Question 31

Co, Ni, Cu, Zn

Answer 31

POTASSIUM CYANIDE

Question 32

Ca, Mg, Al to allow titration of Zn

Answer 32

AMMONIUM FLUORIDE

Question 33

suppress Al-EDTA complex

Answer 33

Triethanolamine

Question 34

inactivate Hg, Cu for titrati- on of Zn

Answer 34

THIOGLYCOL

Question 35

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

Answer 35

DIRECT TITRATION

Question 36

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

Answer 36

RESIDUAL TITRATIONS