Titration PDF

Titration ❑ A technique for determining the concentration of a solution by measuring the volume of one solution needed to completely react with another solution. ❑ Titration process involves addition of solution of known concentration from burette to the measured volume of ana...

Titration ❑ A technique for determining the concentration of a solution by measuring the volume of one solution needed to completely react with another solution. ❑ Titration process involves addition of solution of known concentration from burette to the measured volume of analyte. Principle of Titration: It is based on the complete chemical reaction between the analyte and the reagent (titrant) of known concentration. Analyte: The solution of unknown concentration but known volume put in conical flask. Titrant: The solution of known concentration put in burette. Standard Solution: A solution of known concentration is called the standard solution.  Primary standard solution Secondary standard solution It has certain properties It has certain properties ❑ Extremely pure. ❑ Less pure than primary standard. ❑ Highly stable. ❑ Less stable than primary standard. ❑ It should not be hygroscopic. ❑ Cannot be weighed easily. ❑ It should be stable toward air. ❑ It should not undergo any side- reaction. ❑ Can be weighed easily. ❑ It should be available and not too expensive. Equivalence Point: It is a theoretical point where the amount of two reactants are just equivalent. End Point: It is a practical point at which the reaction is observed to be complete, this point is usually observe with the help of indicator. Indicator An auxiliary substance (either weak acids or weak bases) which helps in the usual detection of the completion of the titration process at the end point. acid-base titrations, are generally used indicators. They change their color within a certain pH range. Acid – base Titration (neutralization) A sample of unknown concentration of acid is estimated with a known concentrated base or vice-verse. In this experiment, we will quantitatively study an acid-base reaction. Strong acids and strong bases dissociate completely in water. Determination normality of sodium hydroxide solution by a standard solution of hydrochloric acid. HCl reacts with sodium hydroxide according to the following equation: The eq.wt. of both the HCl and NaOH is equal to their molecular weights. Note// Both the acid and base are strong, any indicator may be used. Glassware ❑ Burette ❑ Stand ❑ Conical flask ❑ Funnel ❑ Beaker ❑ Pipette ❑ Graduated Cylinder ❑ Dropper ❑ Washing bottle. Materials ❑ HCl solution (standard) known normality. ❑ NaOH solution of unknown normality. ❑ Phenol naphthalene indicator. Procedure Standardization of the NaOH solution by titrating with standard of HCl solution: 1- Transfer by a pipette 5 ml of unknown NaOH solution to a conical flask. 2- Add to the conical flask two or three drops of phenol naphthalene indicator. 3- Fill the burette with HCl solution to zero mark. 4- Titrate NaOH against HCl until the color of solution changes from colorless to pink. 5- Repeat the experiment three times and record your results. Calculations 1. Titrations results Titrations 1(trial) 2 3 Final burette reading(ml) Initial burette reading(ml) Volume of HCI (ml) The volume of NaOH used in three times is 5 ml. 2. Average volume of HCl used = (calculated from burette). 𝑽𝟏 + 𝑽𝟐 + 𝑽𝟑 𝑽 𝒂𝒗𝒆𝒓𝒂𝒈𝒆 = 𝟑 3. Then the unknown concentration calculated by using the law: (𝑵𝟏 × 𝑽𝟏 )𝑯𝑪𝑰 = (𝑵𝟐 × 𝑽𝟐 )𝑵𝒂𝑶𝑯