M3-1 INTRODUCTION TO TITRIMETRIC ANALYSIS; NEUTRALIZATION TITRATIONS - PART 2 - Flashcards
Amount of active constituent in sample
ANALYTE
Amount of solution with known concentration
STANDARD SOLUTION
Chemical Equivalence
end point
Analytical method
TITRIMETRY (Titrimetric Analysis)
what substance is added in the Erlenmeyer flask?
Analyte or Sample
Have an unknown concentration of the active constituent
Analyte or Sample
Physical change
end point
ASSAY
= TITRANT?
STANDARD SOLUTION
also known as stock solution
standard working solution
ASSAY
= TITRAND?
ANALYTE
STAN’ZN
= TITRANT?
STANDARD WORKING SOLUTION
amount of added titrant is chemically equivalent to the amount of analyte in the sample
Equivalence Point
STAN’ZN
= TITRAND?
PRIMARY STANDARD/ SECONDARY STANDARD
Types of Analysis based on Reaction:
- Neutralization
a) Acidimetry
b) Alkalimetry - Precipitation
- Redox
- Complexation
substance being titrated at Erlenmeyer flask
Titrand
solution added from the buret
Titrant
A highly pure substance
+ Dried solid
PRIMARY STANDARD
Usually, a solution with known concentration
+ liquid
SECONDARY STANDARD
Methods of Titration
- Direct Titration
- Residual (Back) Titration
- Blank Titration
Titrant is added to analyte until a reaction goes to completion
DIRECT TITRATION
+ consists of onky one titrant only
+ until physical change (endpoint) occurs
+ titrant (Standard solution)
+ titrand (Analyte)
! Standardization employs direct titration
DIRECT TITRATION
Type of Acid-Base Titrimetry
- ACIDIMETRY
- ALKALIMETRY
Type of Analysis →
Opposite of Unknown (analyte)
Analysis of “bases (analyte)” using an accurately measured volume of “acid (standard solution)”
+ Titrant - acid
+ Titrand (Analyte) - base
ACIDIMETRY
Analysis of “acids (analyte)” using an accurately measured volume of “base (standard solution)”
+ Titrant - base
+ Titrand (Analyte) - acid
ALKALIMETRY
Assay of Sodium bicarbonate
+ Titrant - ?
+ Titrand (Analyte) - ?
+ Type of Analysis: ?
+ Titrant - acid (0.1N H2SO4)
+ Titrand (Analyte) - base (NaHCO3)
+ Type of Reaction: Acidimetry
UNKNOWN
ANALYTE
KNOWN
STANDARD SOLUTION
Assay of Hydrochloric acid
+ Titrant - ?
+ Titrand (Analyte) - ?
+ Type of Analysis: ?
+ Titrant - base (1N NaOH)
+ Titrand (Analyte) - acid (HCl)
+ Type of Reaction: Alkalimetry
In a __________, the titrant and titrand are opposite in nature (i.e. acid-base).
direct titration
Assay of Boric acid
(ACIDIMETRY or ALKALIMETRY)
Analyte: boric acid (acid) → ALKALIMETRY
Assay of NaOH
(ACIDIMETRY or ALKALIMETRY)
Analyte: NaOH (base) → ACIDIMETRY
Assay of Tartaric acid
(ACIDIMETRY or ALKALIMETRY)
Analyte: tartaric acid (acid)→ ALKALIMETRY
*Used to determine the “%content or purity” of a substance (analyte) in a given sample employing [ direct titration ]
%𝑨 =
𝒎𝑳 𝒙 𝑵 𝒙 𝒎𝑬𝒒 𝒘𝒕
————————– 𝒙 𝟏𝟎𝟎
𝒈𝒔𝒙
This method is used if:
1. there is a “large difference” between equivalence and end points (also called titration error)
2. when the sample is “insoluble” in water
3. when the reaction between the titrant and analyte is “slow”
RESIDUAL TITRATION
(Back titration
large difference between equivalence and end points
titration error
- Excess reagent is added to the
analyte and the excess is determined. - Composed of:
– One (1) analyte
– Two (2) standard solutions → RESIDUAL - Excess reagent/solution
- Back titrant solution
RESIDUAL TITRATION
(Back titration)
Assay of Milk of Magnesia (MOM)
(2 standards solutions used; NaOH and H2SO4)
+ Titrant - ?
+ Titrand (Analyte) - ?
+ Excess - ?
+ Type of Analysis: ?
+ Titrant - Base(1N NaOH)
+ Titrand (Analyte) - base (Mg(OH)2)
+ Excess - acid (1N H2SO4)
+ Type of Reaction: Residual Acidimetry
Assay of Aspirin tablets
(2 standards solutions used; NaOH and H2SO4)
+ Titrant - ?
+ Titrand (Analyte) - ?
+ Excess - ?
+ Type of Analysis: ?
+ Titrant - Acid (aspirin)
+ Titrand (Analyte) - Acid (H2SO4)
+ Excess - Base (NaOH)
+ Type of Reaction: Residual Alkalimetry
ASSAY (Direct)
ACIDIMETRY
Analyte: Base
Titrant: Acid
ALKALIMETRY
Analyte: Acid
Titrant: Base
ASSAY (Residual)
ACIDIMETRY
Analyte: Base
Titrant: Base
Excess: Acid
ALKALIMETRY
Analyte: Acid
Titrant: Acid
Excess: Base
! Remember
Assay of Zinc oxide
(2 standards solutions used; NaOH and H2SO4)
+ Titrant - ?
+ Titrand (Analyte) - ?
+ Excess - ?
+ Type of Analysis: ?
+ Titrant - Zinc oxide (base)
+ Titrand (Analyte) - NaOH (base)
+ Excess - H2SO4 (acid)
+ Type of Analysis: Residual Acidimetry
*Used to determine the “%content or purity” of a substance (analyte) in a given sample using [ residual or back titration ]
%𝑨 =
𝑵𝒙𝒔𝑽𝒙𝒔 − 𝑵𝒕𝑽𝒕 𝒙 𝒎𝑬𝒒 𝒘𝒕
————————————— 𝒙 𝟏𝟎𝟎
𝒈𝒔𝒙
𝒙𝒔 → 𝒆𝒙𝒄𝒆𝒔𝒔 𝒕 → 𝒕𝒊𝒕𝒓𝒂𝒏�
Performed using the same quantities of the same reagent treated in the same manner,
[ but without the analyte ]
No Analyte
*Contains diluent, indicator etc
BLANK TITRATION
Formula for 𝒎𝑬𝒒 𝒘𝒕
𝒎𝑬𝒒 𝒘𝒕 =
MW
—————-
feq x 1000
- Used to “detect impurities”
- The volume used in blank is ‘subtracted from’ to actual volume to compensate this error
BLANK TITRATION
Analysis of bases using an accurately measured volume of acid
A. Acidimetry
B. Alkalimetry
C. Argentometry
D. Compleximetry
A. Acidimetry
Type of analysis where an acidic sample is treated with an excess standard base, and the unreacted base is titrated with a standard acid.
A. Direct Acidimetry
B. Direct Alkalimetry
C. Residual Acidimetry
D. Residual Alkalimetry
D. Residual Alkalimetry
In the residual titration of magnesium hydroxide, which of the following solution is used as the back-titrant?
A. Hydrochloric acid
B. Sodium hydroxide
C. Sulfuric acid
D. Water
B. Sodium hydroxide
A 0.1 g sample of a sodium carbonate was dissolved in 50 mL of 0.1 N HCl and boiled to eliminate CO2. Back-titration of the excess HCl required 24 mL of 0.09 N NaOH.Identify what type of analysis is employed.
A. Direct Acidimetry
B. Direct Alkalimetry
C. Residual Acidimetry
D. Residual Alkalimetry
C. Residual Acidimetry
