Chemistry Practicals

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2011 - 2012

Table of Contents

|Page |Title |Module |Skills tested | |# | | | | |3 |Standardisation of hydrochloric acid |2 | | |5 |Calibration of a pipette |2 |ORR, A&I | |6 |Redox Titration / H2O2 vs KMnO4 |2 |M&M, A&I | |8 |Back Titration |2 | | |10 |Gravimetric analysis of hydrated salt |2 | | |11 |Flame tests |2 | | |12 |Reactions of cyclohexane and cyclohexene |1 |ORR,A&I | |14 |Paper Chromatography |2 | | |15 |Water polluting inorganic ions |3 | | |16 |Distillation of a sample of rum |3 | | |17 |Salted peanuts “Fuller” |2 |P&D | |17 |Antique or Fake |2 |P&D | |17 |Margarine vs Butter |1 |P&D | |18 |Identity of sample X |3 |M&M, ORR, A&I |




AIM: The purpose of this experiment is to determine the concentration of a solution of hydrochloric acid using a standard solution of sodium carbonate.

Introduction: The salt reacts with hydrochloric acid in a 1: 2 molar ratio (1 mole sodium carbonate : 2 moles acid). In this experiment you will prepare a standard solution of sodium carbonate and titrate this solution against a solution of hydrochloric acid of unknown concentration using methyl orange as indicator.

Procedure A: Preparation of the standard solution.
1. Weigh 2.0 g of sodium carbonate to the nearest 0.01g. Dissolve the solid in the minimum amount of water. 2. Record your readings in the table below.
3. Transfer the solid and washings to a volumetric flask. Your teacher will guide you. 4. Add distilled water, swirling at intervals to mix the contents, until the level is within 1 cm of the calibration mark on the neck of the flask. 5. Using a wash bottle, carefully add distilled water to bring the bottom of the meniscus to the mark. 6. Insert the stopper and shake thoroughly (by inversion) to ensure complete mixing.

Procedure B:
1. Rinse and fill the burette with hydrochloric acid solution. Record the initial burette reading. 2. Using a pipette filler, rinse the pipette with some of the sodium carbonate solution and carefully transfer 25cm3 of the solution to a clean conical flask. 3. Add 2 drops of the methyl orange indicator and swirl the flask. 4. Run hydrochloric acid from the burette into the flask, with swirling until an orange colour (with a hint of pink) permanent colouration is seen. Record the burette reading. 5. Repeat the titrations as many times as is necessary to obtain consistent results. 6. Do...
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