Acid-Base Titrations Overview

Acid-Base Titrations

• Standard solutions are solutions with a known concentration and composition.
• Primary Standard is a solution of exactly known concentration.
  • It is used to accurately determine the concentration of other solutions.
• Requirements for a primary standard substance:
  • Must be easily obtainable in a high grade of purity and of known composition.
  • Stable and resists reactions with air.
  • Not deliquescent or hygroscopic, and not volatile.
  • Can be dried at 105-110°C without decomposition.
  • Has a relatively high molecular weight.
  • Reacts quantitatively with other substances.
• Examples of primary standard substances:
  • Acids: Potassium acid phthalate, oxalic acid, benzoic acid.
  • Bases: Sodium carbonate, Borax (sodium borate).
• Secondary Standard is a solution with an approximately known concentration.
  • Its exact concentration is determined through a process called standardization.
  • Standardization involves titrating the secondary standard solution against a primary standard solution or a previously standardized secondary standard.
• Examples of secondary standard substances:
  • HCl and NaOH.

Expressing Concentration of Standard Solutions

• Molarity (M):
  • Number of moles of solute per 1 Liter of solution.
  • Formula: M = (Number of moles of solute) / (Volume in L of solution)
• Normality (N):
  • Number of equivalent weights of solute per 1 Liter of solution.
  • Formula: N = (Number of equivalent weights of solute) / (Volume in L of solution)

Definition of Mole

• For molecules:
  • The mole is gram-molecular weight (molecular weight expressed in grams).
• For atoms:
  • The mole is gram-atomic weight (atomic weight expressed in grams).

Definition of Equivalent Weight

• The weight of a substance that is equivalent in its reactive power to 1 mole of hydrogen.
• Calculation of equivalent weight depends on the type of reaction.
• This lecture focuses on acid-base reactions.