EXPERIMENT 7-SUPPLEMENTARY QUESTIONS ANALYZING THE CONCENTRATION OF AN UNKNOWN A

Question

EXPERIMENT 7-SUPPLEMENTARY QUESTIONS ANALYZING THE CONCENTRATION OF AN UNKNOWN ACID 1 Would the calculated molarity of the unknown acid solution be higher, lower, or not affected if each of the following occurred. Explain your answers. a. The buret containing NaOH was rinsed with distilled water but not rinsed with NaOH before being filled. b. Your lab instructor miscalculated the Molarity of the NaOH solution you used in the titration (the true molarity was higher than calculated by your instructor). The tip of the NaOH buret contained an air bubble at the beginning of the titration but not at the end. c. 2) Suppose you used an unknown H:SO, concentration instead of HCI. What changes would need be made to the calculations of the concentration of the acid?

Explanation / Answer

a. If the buret is not rinsed with NaOH, the leftover water would mix with NaOH and dilute the actual concentration of NaOH. As a result, more NaOH would be needed to reach the equivalence point. more moles of NaOH means more moles of HCl. So the molarity of the acid awould be high, as a result.

b. If the true molarity of NaOH is higher than the molarity used for titration, then lesser moles of NaOH would be used, and hence lesser moles of acid and the acid molarity also would be lower.

c. If there is an air bubble in the burette, the volume of NaOH used will be higher than the actual required. Which lead to an increase in moles of acid and thus the molarity of acid.

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