Certain Chemical Industry company has a quality control job opening. The job is

Question

Certain Chemical Industry company has a quality control job opening. The job is open for any major with basic knowledge of chemistry. You decided to apply and you sent your CV. In the interview the HR personnel gives you a sealed folder from a certain lot to test your laboratory experience, as well as your quantitative and volumetric analysis skills. The chemical contained in the sample is benzoic acid (C_7H_6O_2). and it is known to be a monoprotic acid. In order to get the job you need to determine if the sample's purity is acceptable based on their standards. Inside the folder you found a vial with a solid sample labeled BA-I, a periodic table, and the following data: 1.250 g of the sample required 20.15 mL of 0.500 M concentration of NaOH to reach the end point. The lot can be denied if the purity is below 99.5% purity. What is the purity in the sample? It is the purity acceptable? Would you repeat the titration experiment? Explain.

Explanation / Answer

C6H5COOH + NaOH = C6H5COONa + H2O

Molar mass of C6H5COOH = 122.12134 g/mol

Molar mass Of NaOH = 39.99710928 g/mol

moles of NaOH = 0.02015 X 0.500 = 0.0100 moles

It should react with 0.0100 moles of C6H5COOH

Converting moles to g = 1.2212

now, percentage purity = 1.221/1.250 X 100 = 97.68 %

This purity is not acceptable.

Yes, the experiment should be repeated atleast thrice, to check if there was no manual error in determination.

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