How would these actions affect your calculated value for concenration of the unk

Question

How would these actions affect your calculated value for concenration of the unknown oxalic acid solution, H2C2O4?  (please use complete sentences)

A. You did not rinse the buret with KMnO4 solution after washing the buret with water and before you began the titration.

B. You thought that you had reached the end point, stopped adding titrant and recorded the buret readig but then noticed the color faded in about 15 seconds.

C. You used an old KMnO4 solution that had been labeled 0.022 M instead of preparing your own fresh solution to determine the concentration of oxalic acid.

D. Your computed relative precision of measuremnt is twice the magnitude of the precsion obtained another one of your lab groups.          

Explanation / Answer

actions affect your calculated value for concenration of the unknown oxalic acid solution, H2C2O4?

A. You did not rinse the buret with KMnO4 solution after washing the buret with water and before you began the titration. Ansewr = due to the presence of small amount of water KMnO4 will be diluted and concentration of oxalic acid will be more.

B. You thought that you had reached the end point, stopped adding titrant and recorded the buret readig but then noticed the color faded in about 15 seconds.Answer = Oxalic acid concentration will be less.

C. You used an old KMnO4 solution that had been labeled 0.022 M instead of preparing your own fresh solution to determine the concentration of oxalic acid. Answer = concentration of oxalic acid is less observed.

D. Your computed relative precision of measuremnt is twice the magnitude of the precsion obtained another one of your lab groups. Answer = oxalic acid concentration is more.

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