The Tollen’s test for the presence of reducing sugars (say, in a urine sample) i
ID: 487964 • Letter: T
Question
The Tollen’s test for the presence of reducing sugars (say, in a urine sample) involves treating the sample with silver ions in aqueous ammonia. The result is the formation of a silver mirror within the reaction vessel if a reducing sugar is present. Using glucose to illustrate this test, the redox reaction occurring is
C6H12O6 (aq) + 2 Ag+1 (aq) + 2OH -1 (aq) à C6H12O7 (aq) + 2 Ag(s) + H2O (l)
What has been oxidized?
What has been reduced?
What is the oxidizing agent?
What is the reducing agent?
Show/ explain how you derived your answer.
Explanation / Answer
Glucose is converting into gluconic acid. Glucose is here oxidized. (addition of oxygen is is called oxidation).
Silver is reduced here (decrease in oxidation number from +1 to 0)
Here silver is oxidizing agent (it is going reduction and oxidizing glucose)
Here glucose is reducing agent (glucose is going oxidation and redcuing silver)