Preparation and Standardization of 0.1 M Naoh Using Khp

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Preparation and standardization of 0.1 M NaOH using KHP|
Analysis of unknown solid containing KHP|
Steanie Rodriguez|

CHEM-C311 Analytical Chemistry Laboratory
July 7, 2011
The main purpose of this experiment is to identify an unknown organic acid by conducting various experiments to determine the acid’s unique properties. By determining selected constant properties of the unknown and then comparing these properties to the constant properties of known substances, it is possible to identify an unknown substance. The properties used to identify the unknown must be intensive, or independent of amount. Both chemical properties and physical properties are intensive properties used in determining the identity of an unknown.

This is a 1:1 titration. One mole of base will titrate one mole of acid. The endpoint of the titration will be determined by an indicator, phenolphthalein. Phenolphthalein is a weaker acid than KHP. It is colorless under acidic conditions and changes to a pink color under basic conditions. Therefore, the first persistent presence of color indicates that it is beginning to titrate the indicator and have reached the endpoint; if the solution changes to a dark pink color, the solution has overshot the endpoint. The formula of KHP is C8H5O4K.

In this experiment, a sample of KHP of unknown purity will be analyzed by titration with a standardized NaOH solution. The reaction is shown below:

C8H5O4K (aq) + OH- → C8H4O42-(aq) + H2O(l) + K+

Table 1- Part B|
| Trial 1| Trial 2| Trial 3|
Mass KHP (g)| 0.7137 ± 0.0001| 0.7275 ± 0.0001| 0.7110 ± 0.0001| Volume NaOH (mL)| 34.43 ± 0.05| 36.45 ± 0.05| 35.52 ± 0.05| Mass to Volume ratios| 0.02073| 0.01996 | 0.02002 |
Standard Dev. of ratios| ± 0.0004|
Mean ratio| 0.02024|

Table 2- Part C|
| Trial 1| Trial 2| Trial 3|
Mass of unknown#3 (g)| 1.2019 ± 0.0001| 1.2556 ± 0.0001| 1.2019 ±...
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