Online Lab _14B titration curve.docx - Lab#14B Acid-Base...

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Lab #14B: Acid-Base Titration Curves Purpose In this experiment you will use a volumetric titration to determine the titration curve for a weak acid. You will determine the equivalence point for the acid and calculate the molar concentration of the acid solution. Materials Chemicals Ammonia solution- NH 3 (1M) ( SDS ) Vinegar Equipment from Home Distilled water Cell phone camera Clear tape to secure syringe Microsoft Excel or another spreadsheet program Equipment from Kit Goggles & gloves 50 mL & 10 mL graduated cylinders 250 mL & 150 mL beakers pH meter & buffer solutions syringe and stopcock funnel pipettes Introduction Acid-Base titration curves are graphs that show the successive pH values that occur during the titration of a base with an acid or an acid with a base. The general purpose of a titration is to determine the amount of a particular substance in a sample. An acid-base titration curve can be used to find the equivalence point, which is the point where equal stoichiometric moles of been added. The volume of base added (titrant) at the equivalence point can be used to find the moles of acid in an unknown solution. An Acid-Base titration curve will vary depending on the strength of the acids and bases. When a strong acid is titrated with a strong base, the curve will rise sharply and have an equivalence point at pH = 7. If a weak acid is titrated with a strong base or a weak base is titrated with a strong acid the titration curve is unique because one of the ions in the salt formed will often hydrolyze in water. For a weak acid, the equivalence point will be at a pH higher than 7. For a weak base it will be lower than 7. Volumetric Titration Lab #15 1
A titration is a process used to determine the volume of a standard solution that is needed to react with a given amount of another substance. In this experiment, your goal is to determine the molar concentration of an acid solution by conducting titrations with a base of known concentration. You will be testing a weak acid found in vinegar, acetic acid (HC 2 H 3 O 2 ). You will use ammonia (NH 3 ) solution as your base of known concentration. The reaction equation is shown below in net ionic form. HC 2 H 3 O 2 (aq) + NH 3 (aq) NH 4 + (aq) + C 2 H 3 O 2 (aq) Notice that a double arrow is used since this is a reversible reaction, or equilibrium, since it is a weak acid. A weak acid is one that doesn’t completely dissociate in solution.

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