Oxidation and Reduction

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TITRATION OF SULPHURIC ACID WITH SODIUM HYDROXIDE Modified: November 3, 2002 INTRODUCTION A TITRATION is a process in which a measured amount of a solution is reacted with a known volume of another solution (one of the solutions has an unknown concentration) until a desired end point is reached. (The “end point” of a titration is the point in the titration at which an indicator dye just changes colour to signal the stopping point of the titration.) In this experiment, you will use a PIPETTE to measure some sulphuric acid into a beaker. The sulphuric acid has an unknown concentration. Then you will fill a BURETTE with sodium hydroxide (a base) that has a known concentration. Because all the reactants and products in this reaction are colourless, an INDICATOR DYE is added to the sulphuric acid to let us know when all the acid present has been EXACTLY NEUTRALIZED by adding base. Finally, the sodium hydroxide in the burette is added to the acid/indicator solution until the indicator changes colour. (An indicator dye is a chemical that has a different colour in an acid and a base.) PROCEDURE 1. Get the following equipment for your group: burette pipette syringe with piece of rubber tubing attached 1–250 mL beaker 3–100 mL beakers grease pencil stand and burette clamp Each beaker must be clean and dry. Label one 100 mL beaker “ACID”, one “BASE” and one “RINSE”. 2. Pour about 80 mL of NaOH solution into the BASE beaker. Record the NaOH concentration. 3. Prepare the burette as follows. Hold the burette in one hand and pour about 5 mL from the BASE beaker into the burette. Hold the burette almost horizontally and roll the burette back and forth between your fingers so as to coat the inside of the burette with base solution. Pour the solution in the burette into the sink. Repeat the process with a second 5 mL portion of NaOH solution. Finally, rinse the burette a

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