M3-1 INTRODUCTION TO TITRIMETRIC ANALYSIS; NEUTRALIZATION TITRATIONS - PART 1 - Flashcards
(Volume and concentration)
Solution
- amount
- concentration
- % purity
sample
method of determining the
quantity of a reagent of known concentration (STANDARD SOLUTION) that is required to react completely with the amount of active constituent is sample being analyzed (analyte)
Analytical method
known concentration
STANDARD SOLUTION
sample being analyzed
analyte
Acetic acid
VINEGAR
- solution added from the buret
Titrant
sodium hydroxide
Base
Acetic acid
(Analyte or Standard Solution?)
ANALYTE
NaOH
(Analyte or Standard Solution?)
STANDARD SOLUTION
mass
ANALYTE
A process in which a standard reagent is added to a solution of analyte until the reaction is judged to be complete.
TITRATION
solution of known concentration
- Standard solution
Sodium acetate
Salt
–substance in a sample being analyzed
Analyte
- substance being titrated
Titrand
Analysis
ASSAY
Content/purity not yet determined
UNKNOWN
Neutralization (Acid-Base) Reaction
Acid + Base → Salt + Water
Known Concentration
KNOWN
Indicator of Acetic acid in Vinegar sample
Phenolphthalein
During ASSAY
The standard solution is considered
as the ___________; while the
analyte/sample as the __________
TITRANT - SS
TITRAND - Analyte
- Determine the analyte.
1. Paracetamol in Biogesic tablet.
2. Caffeine in Coffee powder
3. Calcium ions in mineral water
Biogesic Tablet
Coffee powder
Mineral water
When a physical change occurs that is associated with the condition of equivalence
End point
When the amount of added titrant is chemically equivalent to the amount of analyte in the sample
Equivalence Point
- Acid base indicators are mostly complex organic molecules which are either weak acid or weak bases
- Added to the analyte solution to give an [observable physical change.]
Indicators
Acid → Low pH values; pH < 7
Neutral → pH = 7
Base/alkali → High pH values; pH > 7
Ph Values
Low pH values; pH < 7
Acid
pH = 7
Neutral
High pH values; pH > 7
Base/alkali
Rules for the Use of Indicators
- Two (2) drops
- SA (titrant) + SB (titrand) → MO, MR, PP
- SB (titrant) + WA (titrand) → PP
- SA (titrant) + WB (titrand) → MO
- WA (titrant) + WB (titrand) → N/A
- Appearance of color is preferred.
just be familiar
Indicator of Sodium bicarbonate, NaHCO3
METHYL RED
0.1N H2SO4
Acid
NaHCO3
Base
An ideal standard solution should be
- Stable
- Reacts rapidly
- Reacts completely
- Selective
Used to establish the [concentration] of a solution by titrating it against a [primary standard.]
Standardization
highly purified compound that serves a reference material
– Primary Standard
Primary Standard
- High purity
- Stable
- Modest cost
- Soluble in medium
- High MW
Sulfuric acid solution is considered a
SECONDARY STANDARD
is a substance whose content/purity/concentration has been found by comparison against a primary standard
secondary standard
Remember: H2SO4 was standardized using Na2CO3
(a primary standard).
n/a
- A highly pure substance
- Dried solid
- Ex. Sodium carbonate
PRIMARY STANDARD
- Usually, a solution with known concentration
- Standard Solution (liquid)
- Ex. Sulfuric acid solution
SECONDARY STANDARD
– It is defined as the number of equivalents of solute per liter of solution.
– Or milliequivalents per milliliter (mEq/mL)
𝑵 = 𝑬𝒒/𝑳
𝒐𝒓 𝒎𝑬𝒒/𝒎𝑳
Normality (N)
– It is defined as the number of moles of solute per liter of solution.
– Or millimoles per milliliter (mmol/mL)
𝑴 = 𝒎𝒐𝒍/𝑳
𝒐𝒓 𝒎𝒎𝒐𝒍/𝒎𝑳
Molarity (M)
𝒎𝑬𝒒 𝒘𝒕 =
𝑴𝑾/𝒇𝒆𝒒 𝒙 𝟏𝟎𝟎0
𝑬𝒒𝒖𝒊𝒗𝒂𝒍𝒆𝒏𝒄𝒆 𝑭𝒂𝒄𝒕𝒐𝒓 = 𝒇𝒆𝒒 = 𝒗𝒂𝒍𝒆𝒏𝒄𝒆
– For neutralization reactions, feq represents the number of reacting H+ or OH- ions
Milliequivalent Weight (mEq wt)
Equivalence Factor (feq)
- For acids:
feq = no. of reactive H+
– HCl - feq = 1
– H2
SO4 - feq = 2
- For bases:
feq = no. of reactive OH-
– Mg(OH)2 - feq = 2
– NaOH - feq = 1
Types of Analysis based on Reaction
- Neutralization
a) Acidimetry
b) Alkalimetry - Precipitation
- Redox
- Complexation
