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Analysis of Unknown Acetic Acid Solution

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Analysis of Unknown Acetic Acid Solution

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  • June 2013
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TITLE :
* Analysis of an unknown acetic acid solution
OBJECTIVES :
* To prepare the sodium hydroxide solution, NaOH
* To standardise the base against potassium hydrogen phthalate * To analyse the unknown acetic acid
RESULTS :
A. Preparation of the sodium hydroxide solution

Volume of NaOH taken from the stock solution = 3.33 mL

B. Standardisation of the base against potassium hydrogen phthalate

| 1| 2| 3|
Weight KHP| 1.0000| 1.0004| 1.0006|
Final volume of NaOH (mL)| 22.6| 22.2| 21.7|
Initial volume of NaOH (mL)| 0| 0| 0|
Volume of NaOH (mL) used| 22.6| 22.2| 21.7|
Ratio volume of NaOH/weight of KHP| | | |

C. Analysis of the unknown acetic acid solution

| 1| 2| 3|
Volume of unknown acetic acid (mL)| 10| 10| 10|
Final volume of standard NaOH (mL)| 42.5| 42.8| 43.0|
Initial volume of standard NaOH (mL)| 0| 0| 0|
Volume of standard NaOH (mL) used| | | |

DISCUSSIONS:
Sodium hydroxide is a hygroscopic solid which means it absorbs water from the air. A weighed quantity of sodium hydroxide therefore contains an unknown mass of water. Therefore, a solution of known molarity cannot be made by dissolving unknown mass of solid sodium hydroxide in water. The concentration of the sodium hydroxide solution in water must be determined experimentally. This is done by titrating the sodium hydroxide solution against a primary standard. A primary standard is a substance from which a solution of known concentration can be prepared. The concentration of sodium hydroxide prepared is 18.75M with volume of 3.3mL. The primary standard used in this experiment is potassium hydrogen phthalate,C6H4COOHCOOK, which is referred to by the shorthand notation of “KHP”. KHP has several advantages: it does not absorb moisture readily; it is easily dried; it can be accurately weighed; it can be obtained in very pure form; it has a high molar mass of 204.22 g/mole; and it is very soluble...

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