HUE Clinical 2024 Acid-Base Titration PDF

Pharmaceutical Analytical Chemistry I (PC 111) Level I Students (Clinical Pharm D) Acid-Base Titrations  Acid-Base Titrations General Objectives After this Lecture, you should know: ◼Types of Standard Solutions [Primary & Secondary]. ◼Methods...

Pharmaceutical Analytical Chemistry I (PC 111) Level I Students (Clinical Pharm D) Acid-Base Titrations  Acid-Base Titrations General Objectives After this Lecture, you should know: ◼Types of Standard Solutions [Primary & Secondary]. ◼Methods of expressing concentration of standard solution. ◼Important mathematical equations. 2  Acid-Base Titrations Standard Solutions ◼ Standard solutions are solutions of known concentration and composition. ◼Standard solutions are classified into 2 types: (1) Primary Standard ◼ It is a solution of exactly known concentration and composition. ◼ Its concentration remains constant for a long period. ◼ It can be directly prepared by weighing an exact weight of the primary standard substance in a measuring (volumetric) flask and dissolving it in a proper solvent. 3  Acid-Base Titrations Requirements of a primary standard substance 1- It must be easily obtained in a very high grade of purity and of known composition. 2- Very stable and resists reactions with air. 3- Not deliquescent (not hygroscopic) and non volatile. 4- It can be dried at 105-110°C without decomposition. 5- It should have a relatively high molecular weight to minimize weighing error. 4  Acid-Base Titrations Requirements of a primary standard substance: 6- It must react with other substances in a quantitative way according to balanced chemical equations. Examples of primary standard substances: ❑ Acids: Potassium acid phthalate - Oxalic acid - Benzoic acid. ❑Bases: Sodium carbonate - Borax (sodium borate). 5  Acid-Base Titrations (2) Secondary Standard ◼ It is a solution of an approximately known concentration. ◼ Its concentration can not be directly calculated from the weight of solute and volume of solution. [Remember: Solute + Solvent = Solution] ◼ Its exact concentration is determined by a process called “Standardization”. ◼ Standardization: is a process used to determine the exact concentration of secondary standard solutions and correct any error if present. ◼ That is done by: Titrating the 2ry standard solution against a 1ry standard solution OR against a previously standardized 2ry standard. (Q. Give name?) ◼ Examples: HCl and NaOH 6  Acid-Base Titrations Methods of expressing concentration of standard solutions The most common methods are: Molarity (M) & Normality (N). (1) Molarity or Molar concentration (M): ▪ It is the number of moles of the solute per 1 liter of the solution. ▪ It is a solution of the substance containing one gram molecular weight of the solute per 1 liter of the solution. 𝑵𝒖𝒎𝒃𝒆𝒓 𝒐𝒇 𝒎𝒐𝒍𝒆𝒔 𝒐𝒇 𝒔𝒐𝒍𝒖𝒕𝒆 M= 𝑽𝒐𝒍𝒖𝒎𝒆 𝒊𝒏 𝑳 𝒐𝒇 𝒔𝒐𝒍𝒖𝒕𝒊𝒐𝒏 Example: 0.5 M NaOH means 0.5 mole of NaOH / 1 L solution. 7  Acid-Base Titrations Definition of Mole (mol.) ◼ For molecules(e.g.: NaOH ):The mole is gram-molecular weight {i.e. molecular wt. expressed in grams}. ◼ For atoms (e.g.: Na): The mole is gram-atomic weight {i.e. atomic wt. expressed in grams}. Examples: If the mol. wt. of NaOH = 40 then 1 mole of NaOH means 40 g NaOH. (i.e. The weight of 1 mole of NaOH is 40 g) If the atomic weight of Na =23 then 1 mole of Na means 23 g Na. (i.e. The weight of 1 mole of Na is 23 g) 8 Acid-Base Titrations Molarity 9  Acid-Base Titrations (2) Normality or Normal concentration (N) ▪ It is the number of equivalent weights of the solute per 1 liter of the solution. ▪ A solution that contains one gram equivalent weight of solute per 1 liter of the solution. 𝑵𝒖𝒎𝒃𝒆𝒓 𝒐𝒇 𝒆𝒒𝒖𝒊𝒗. 𝒘𝒆𝒊𝒈𝒉𝒕𝒔 𝒐𝒇 𝒔𝒐𝒍𝒖𝒕𝒆 N= 𝑽𝒐𝒍𝒖𝒎𝒆 𝒊𝒏 𝑳 𝒐𝒇 𝒔𝒐𝒍𝒖𝒕𝒊𝒐𝒏 Example: 2 N HCl (means 2 equivalent weights of HCl / 1 L solution). 10 Acid-Base Titrations Normality 11  Acid-Base Titrations Definition of Equivalent Weight ◼ It is the weight of the substance that is equivalent in its reactive power to 1 mole of hydrogen. ◼ The exact definition and calculation of equivalent weights differ according to the type of the reaction. We will focus in this lecture on acid-base reactions. 12  Acid-Base Titrations Calculation of the equivalent weight in acid-base reactions: 13  Acid-Base Titrations Summary of Lecture In the previous lecture, you have studied: Types of Standard Solutions [Primary & Secondary]. Methods of expressing concentration of standard solution. Important mathematical equations. 14  Acid-Base Titrations Thank You 15