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Consider the titration described here: 0.7917 g of anhydrous sodium thiosulphate (Na 2 S 2 O 3 ), previously purified and dried in an oven,

Consider the titration described here:

  • 0.7917 g of anhydrous sodium thiosulphate (Na S O ), previously purified and dried in an oven, is weighed into an erlenmeyer flask.
  • This sample is titrated with a mixture of KIO and KI that contains approximately 0.1 M I . This titration requires 23.56 mL of titrant to reach the endpoint (found with a starch indicator).
  • This same mixture of KIO 3 and Kl is then used to titrate a solution containing an unknown amount of ascorbic acid. This titration requires 37.21 mL of titrant to reach the endpoint (found with a starch indicator).
  • The ascorbic acid sample used in the titration above was prepared by using a 25 mL pipet to deliver an aliquot of the solution into an erlenmeyer flask.

Relevant reactions:

I3 +2 S2032-= 3+ S4062 {ascorbic acid} +I3+ H20 = {dehydroascorbate} + 31+2 H*

Based on this information, what is the concentration (in mol/L) of ascorbic acid in the "unknown" liquid?

13 +2 S20331 +S406 {ascorbic acid} +13 + HO = {dehydroascorbate} + 31 + 2H+

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