Acids, Bases, and Salts

2426 Words Nov 20th, 2012 10 Pages
Experiment #7: Acids, Bases and Salts
Mabag, Viannery D., Mangune, Paolo D.
Chem 14.1, MAB1, Ms. Angelyn del Rosario
March 8, 2010

I. Abstract The experiment allowed students to explore different electrolytes and classify them into acids, bases and salts by using different indicators or by measuring the pH levels of each. The experiment also helped students classify different substances through their conductivity properties. The preparation of a 1 M stock solution from NaOH pellets diluted to a 0.1 M NaOH solution was also utilized in making the students understand the concept of titration. Using 0.1 M NaOH as a standard solution, the concentration of an unknown acid was calculated from the endpoint of an acid-base titration.

II.
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The weight of NaOH pellets needed to make 100.00 mL of 1 M NaOH was calculated. This amount of pellets was weighed in a watch glass, then dissolved in 50 mL water. The solution was transferred to a 100 mL volumetric flask and diluted to the mark with distilled water. A 0.1 M of NaOH was prepared from the available concentration. Using M1V1 = M2V2, the volume of NaOH from available concentration needed to prepare 100 mL of 0.1 M NaOH was calculated. The measured volume was diluted to 100.00 mL with distilled water in a volumetric flask. In the titration proper, a base buret was washed thoroughly with soap and water. It was then rinsed thrice with 3 mL portions of the standard base (0.1 M NaOH). The buret was filled with 0.1 M NaOH and air space at the tip was removed. It was set to zero reading and clamped on the iron stand. A 10 mL aliquot of an unknown acid was transferred into an Erlenmeyer flask. 50 mL of distilled water was added along with 2-3 drops of phenolphthalein. The acid was titrated with the standard base until the first appearance of a permanent light pink coloration. The final volume reading was recorded and the molarity (M) of the unknown acid calculated.

V. Results

A.
|Reagents |Classification |Congo red |
|0.1 M solutions |(On litmus paper) | |
|NaOH |Base |Red |
|NH4Cl

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