QC1 LEC MIDTERMS: Chemical Reactions used in Titrimetry

Formula for Titer Value

Standardization

The determination of the concentration of a solution (N or M)

Standardization

Accomplished by the use of another standard solution known as SECONDARY STANDARD or by the use of known purity substance as PRIMARY STANDARD

Primary Standard

Solid substance used for direct standardization of a solution

Formula for Primary Standard

Secondary Standard

• Liquid substance

• Solution of known concentration

Formula for Secondary Standard

• KHP (Potassium Hydrogen Phthalate)

• Sulfamic Acid

Primary Standard of NaOH

Phenolphthalein

Indicator of NaOH

Sodium Carbonate

Primary Standard of HCl

Phenolphthalein

Indicator of HCl

NaCl (Sodium Chloride)

Primary Standard of Silver Nitrate

Potassium Chromate

Indicator of Silver Nitrate

Calcium Carbonate

Primary Standard of EDTA

Hydroxynaphthol

Indicator of EDTA

Ethylenediaminetetraacetic Acid

EDTA

Sodium Oxalate

Standard Solution of Potassium Permanganate (KMnO₄₎

Arsenic Oxide (As₂O₃)

Primary Standard of Iodine

Starch

Indicator of Iodine

Benzoic Acid

Primary Standard of Sodium Methoxide

Thymol Blue

Indicator of Sodium Methoxide

Arsenic Oxide (As₂O₃)

Primary Standard of Ceric Sulfate

Orthopenanthroline

Indicator of Ceric Sulfate

Sodium Tartrate

Primary Standard of Karl Fisher Reagent

Sodium Hydroxide (NaOH)

Secondary Standard of HCl

Ferric Allum

Indicator of Ammonium Thiocyanate (NH₄SCN)

Silver Nitrate (AgNO₃)

Secondary Standard of Ammonium Thiocyanate (NH₄SCN)

Iodine

Secondary Standard of Sodium Thiosulfate (Na₂S₂O₃)

Starch

Indicator of Sodium Thiosulfate (Na₂S₂O₃)

• Burette

• Pipette

Volumetric Apparatus: To Deliver

• Volumetric Flask

• Graduated Cylinder

Volumetric Apparatus: To Contain

Burette

Graduated glass tubes of uniform bore throughout the whole length

Burette

• Closed at the bottom by glass or stopcock

• Read at lower meniscus (for clear solutions)

• MOHR

• GEISSLER

Types of Burette

MOHR

Type of Burette:

• For bases

• A length of tubing connects a separate tip

• Economical

GEISSLER

Types of Burette:

• Acid burette

• Built in stopcock

• Expensive but more accurate

• Direct Titration

• Residual Titration

Types of Titrations

Direct Titration

One titrant used; one volumetric solution

Residual Titration

• For compounds that reacts too slowly with the titrant and with poor solubility

• Used when direct titration is not practicable

• Used if volatile substances are involved

Residual Titration

Two titrants; two volumetric solution

1st VS

1st VS or 2nd VS: added in excess

2nd VS

1st VS or 2nd VS: used to titrate the excess

Blank Determination

Process of repeating the procedure but omitting the sample

• Neutralization

• Precipitation

• Oxidation-Reduction

• Complexation

Chemical Reactions used in Titrimetry

• Reactions must proceed to completion.

• Reaction must proceed in a stoichiometric manner.

• Suitable endpoint detecting device must be available

• For direct titration, reaction must be rapid so a sharp endpoint is achieved.

4 requirements that must be met if reaction is used

Neutralization

A Chemical process in which an acid (proton donor) reacts with a base (proton acceptor) [Bronsted-Lowry Theory]

Bronsted-Lowry Theory

What theory states that an acid (proton donor) reacts with a base (proton acceptor)

Acid

Acid or Base: Proton Donor

Base

Acid or Base: Proton Acceptor

Water and Salt

Determine the Product

Indicator

Are complex organic compounds used to:

• Determine endpoint

• Determine the pH

• Indicate that a desired change in pH has been effected

0 - 2.0

pH Range: Malachite Green

2.9 - 4.0

pH Range: Methyl Yellow

3.0 - 4.6

pH Range: Bromophenol Blue

3.2 - 4.4

pH Range: Methyl Orange

4.0 - 5.4

pH Range: Bromocresol Green

4.2 - 6.2

pH Range: Methyl Red

5.2 - 6.8

pH Range: Bromocresol Purple

6.0 - 7.6

pH Range: Bromothymol Blue

6.8 - 8.2

pH Range: Phenol Red

7.2 - 8.8

pH Range: Cresol Red

8.0 - 9.2

pH Range: Thymol Blue

8.0 - 10.0

pH Range: Phenolphthalein

9.3 - 10.5

pH Range: Thymolphthalein

• Yellow

• Green

Acid & Base: Malachite Green

• Red

• Yellow

Acid & Base: Methyl Yellow

• Yellow

• Blue

Acid & Base: Bromophenol Blue

• Pink

• Yellow

Acid & Base: Methyl Orange

• Yellow

• Blue

Acid & Base: Bromocresol Green

• Red

• Yellow

Acid & Base: Methyl Red

• Yellow

• Purple

Acid & Base: Bromocresol Purple

• Yellow

• Blue

Acid & Base: Bromothymol Blue

• Yellow

• Red

Acid & Base: Phenol Red

• Yellow

• Red

Acid & Base: Cresol Red

• Yellow

• Blue

Acid & Base: Thymol Blue

• Colorless

• Red

Acid & Base: Phenolphthalein

• Colorless

• Blue

Acid & Base: Thymolphthalein

3 drops

Rules for Using Indicator: Use ____ of indicator TS unless otherwise directed

Strong Acid

Determine: Strong Acid, String Base, Weak Acid, or Weak Base

• Hydriodic Acid (HI)

Strong Acid

Determine: Strong Acid, String Base, Weak Acid, or Weak Base

• Hydrobromic Acid (HBr)

Strong Acid

Determine: Strong Acid, String Base, Weak Acid, or Weak Base

• Hydrochloric Acid (HCl)

Strong Acid

Determine: Strong Acid, String Base, Weak Acid, or Weak Base

• Sulfuric Acid (H₂SO₄)

Strong Acid

Determine: Strong Acid, String Base, Weak Acid, or Weak Base

• Nitric Acid (HNO₃)

Strong Acid

Determine: Strong Acid, String Base, Weak Acid, or Weak Base

• Chloric Acid (HClO₃)

Strong Acid

Determine: Strong Acid, String Base, Weak Acid, or Weak Base

• Perchloric Acid (HClO₄)

Weak Acid

Determine: Strong Acid, String Base, Weak Acid, or Weak Base

• Acetic Acid (CH₃COOH)

Weak Acid

Determine: Strong Acid, String Base, Weak Acid, or Weak Base

• Oxalic Acid (C₂H₂O₄)

Weak Acid

Determine: Strong Acid, String Base, Weak Acid, or Weak Base

• Hydrofluoric Acid (HF)

Weak Acid

Determine: Strong Acid, String Base, Weak Acid, or Weak Base

• Hydrogen Cyanide (HCN)

Strong Base

Determine: Strong Acid, String Base, Weak Acid, or Weak Base

• Sodium Hydroxide (NaOH)

Strong Base

Determine: Strong Acid, String Base, Weak Acid, or Weak Base

• Potassium Hydroxide (KOH)

Weak Base

Determine: Strong Acid, String Base, Weak Acid, or Weak Base

• Alanine (C₃H₅O₂NH₂)

Weak Base

Determine: Strong Acid, String Base, Weak Acid, or Weak Base

• Ammonia (NH₃)

Weak Base

Determine: Strong Acid, String Base, Weak Acid, or Weak Base

• Methylamine (CH₃NH₂)

Weak Base

Determine: Strong Acid, String Base, Weak Acid, or Weak Base

• Pyridine (C₅H₅N)

• Hydrochloric Acid

• Sulfuric Acid

Standard Acid Solution

Hydrochloric Acid (HCl)

Standard Acid Solution:

• Preferably used in titration of compounds that yield a precipitate if used with H₂SO₄

• Ex: Barium Hydroxide

Sulfuric Acid (H₂SO₄)

Standard Acid Solution:

• Preferable in hot titrations (HCl is volatile if heat is applied)

• Sodium Hydroxide (NaOH)

• Potassium Hydroxide (KOH)

• Barium Hydroxide (Ba(OH)₂)

Standard Basic Solutions

NaOH, KOH, Ba(OH)₂

Absorb CO₂ in the air thereby changing rapidly in conc.