CHAPTER 4- Chemical Reactions Used in Titrimetry Flashcards
- determination of N or M of solution
- accomplished SECONDARY STANDARD or PRIMARY STANDARD
Standardization
Use of another standard solution
Secondary Standard
Use of known purity substance
Primary Standard
- The weight of substance chemically equivalent to 1 mL of standard solution express in mg/mL
Titer = N x mEq. wt.
Titer
2 types of Volumetric Apparatus
1.To Deliver
2. To Contain
Burets, Pipets
To Deliver
Volumetric Flask, Graduated Cylinder
To Contain
- Graduated glass tubes of uniform bore throughout the whole length
- Closed at the bottom by glass or stopcock
- Read at lower meniscus (for clear solutions)
Burets
2 Types of Buret
- Mohr
- Geissler
- for bases; a length of tubing connects a separate tip; economical
Mohr
- built in stopcock; expensive but more accurate
Geissler
2 Types of Titration
- Direct Titration
- Residual Titration (Indrect, Back Titration)
one titrant used, one volumetric solution
Direct Titration
two titrants, two volumetric solutions
Residual Titration
1st VS - added in excess
2nd VS - used to titrate the excess
- used whenever the direct titration is not practicable
- for compounds which react too slowly with the titrant and with poor solubility used if volatile substances are involved
Residual Titration
process of repeating the procedure but omitting the sample
Blank Determination
4 Chemical Reactions Used in Titrimetry
- Neutralization
- Precipitation
- Oxidation-Reduction
- Complexation
- The reactions must proceed to completion.
- The reaction must proceed in a stoichiometric manner.
- A suitable endpoint detecting device (indicators, electrode) is available.
- For direct titration, the reaction must be rapid so a sharp endpoint is achieved.
4 Requirements must be met if the reaction is to be used
- a chemical process in which an acid reacts with a base
Ex: HCl + NaOH –> NaCl + H2O
Products: Water and Salt
Neutralization
- are complex organic compounds used to:
- determine the end point
- determine the pH
- indicate that a desired change in pH has been effected
Indicators
-Use 3 drops of indicator TS unlesss otherwise directed
- Strong Acid + Strong Base - use MO, MR, PHP
- Strong Acid + Weak Base - use MR
- Weak Acid + Strong Base - use PHP
- Weak Acid + Weak Base - no indicator, never been titrated
Rules for the Use of Indicators
- Strong Acid - HCl, HNO3, H2SO4, H3PO4
- Strong Base - NaOH, KOH
- Weak Acid - Acetic Acid, Oxalic Acid
- Weak Base - NH3, Alanine (C3H5O2NH2), Methylamine (CH3NH2), Pyridine (C5H5N)
Examples of Rules for the Use of Indicators
direct or residual titrimetric analysis of acids using a base
Alkalimetry
Sample: Acid
Titrant: Base
Direct Titration of Alkalimetry
direct or residual titrimetric analysis of base using a acid
Acidimetry
