Beatty 6092 Practical Revision 2023

PURE CHEMISTRY (6092) PRACTICAL REVISION NOTES 2023 Prepared by: Mr. Yeo CK Page | 1 Beatty Secondary School Secondary 4 Express Name: ______________________ ( ) Class: 4E1 Date: ________ Practical Revision: Volumetric Analysis (Titration) Key Concepts: Titrate solution Q with solution P / Titrate solution Q against solution P. solution P in the burette A. General Tips 1. Rinse the funnel and burette with deionised water before the start of the titration. 2. Check for air bubbles at the tip of the burette / leaking of solution before rinsing with chemicals. 3. Remove the filter funnel before the start of titration. 4. Rinse the pipette with deionised water before placing into the reagent bottle. 5. Check if there is liquid in the pipette filler. Def late it completely to ensure no liquid is trapped inside. 6. Tap the tip of the pipette 3 times into the conical flask to ensure that the maximum volume of solution is pipetted. B. Presentation of Data and Measurement Measurement and Accuracy of Data: apparatus accuracy burette 0.05 cm3 (2 decimal places) pipette 25.0 cm3 (1 decimal place) Presentation of Data (Titre volumes should be consistent within ± 0.20 cm3): titration number rough 1 2 3 final burette reading / cm3 25.10 28.60 24.60 49.20 initial burette reading / cm3 0.00 4.30 0.00 24.60 volume of liquid Q added / cm3 25.10 24.30 24.60 24.60 best titration results ✓ ✓ Results: Average volume of Q used = 24.60 24.60 2 + = 24.60 cm3 (2 decimal places) Volume of P used = 25.0 cm3

PURE CHEMISTRY (6092) PRACTICAL REVISION NOTES 2023 Prepared by: Mr. Yeo CK Page | 2 Key Concepts: C. Types of Indicators and Colour Changes indicators acidic end-point alkaline methyl orange red orange yellow screened methyl orange purple grey green thymolphthalein colourless colourless blue D. Calculations involving titration 1. Percentage composition by mass 2. Percentage yield determines the percentage of product formed [mole of reactant]. 3. Percentage purity determines how much pure substance is found within the sample [mole of product]. 4. Chemical Calculations Formulae Note calculations on dilution [mole in 25 cm3 to mole in 1 dm3 and vice-versa] E. Sources of Error, Effects and Improvement 1. Source of Experimental Error: There may be presence of other soluble impurities in the acid solution pipetted into the conical flask which may react with the alkali from the burette. Effect: The volume of solution used in the burette may be larger than expected. Or There may be presence of other soluble impurities in the acid solution pipetted into the conical flask which may re