Normality of Unknown Base Using Volumetric Titration

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Introduction The purpose of this lab is to determine the normality of an unknown base using a volumetric titration. The volumetric titration used for this experiment consisted of a standard acid called potassium hydrogen phthalate (KHC8H4O4) titrated with a weak unknown base. An acid-base indicator called phenolphthalein is used in order to view the reaction proceeding to completion. The indicator allows visualization of the acid changing colour when the solution has reached the end point. The normality of the unknown base is calculated after the solution has reached the end point. The amount of substance being delivered is calculated in units of equivalents per litre using the formula: VaNa = VbNb Experimental In order to titrate the acid with the unknown base, a solution of the acid was prepared. 5.1722 (±10%)g of potassium hydrogen phthalate acid is obtained using a weighing boat and transferred into a volumetric flask containing 250mL of boiled distilled water. Volumetric flask was shaken several times in order to assist the powder to dissolve. Once dissolved, 24.9734 (± 0.0045)mL of acid was pipetted into an Erlenmeyer flask along with 25mL of cool (recently boiled) distilled water. Three drops of acid-base indicator, phenolphthalein, is added to the acid solution. Acid is titrated with the unknown base from the burette as the Erlenmeyer flask is consistently being swirled. Near the endpoint of 24mL, drops of base are added to the acid solution until a light pink colour persists within the solution. Titration is repeated 3 more times in order to achieve more accurate results. Trials | Initial Volume (mL) | Burette Correction (mL) | Final Volume (mL) | Burette Correction (mL) | Vf - ViTotal Volume (mL) | 1 | 0.21 | -0.002 = 0.208 | 24.45 | -0.051 = 24.399 | 24.191 | 2 | 24.45 | -0.051 = 24.399 | 48.39 | +0.045 = 48.435 | 24.036 | 3 | 0.13 |

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