ll. (20 pts) A 50.00 mL sample containing two unknown anions was titrated using
ID: 874493 • Letter: L
Question
ll. (20 pts) A 50.00 mL sample containing two unknown anions was titrated using 0.1021 M AgNO, in the presence of 1.00 mL produced the following titration curve: 0,1 ol B1 Average Anion Eored (V) 0.800 Agt OCN- 0.410 0.222 VAENoa Added SCN- 0.0895 Br- 0.0713 -0.152 a. (4 pts) In a general sense (using the symbol MX" for the analyte) write out BOTH the titration reaction AND the reduction half reaction actually occurring at the indicator electrode in this titration. Titration: Indicator: b. (5pts) What was the initial concentration of the second anion titrated? (o pts) Based on the given list of possible anions, what is the identity of the second anion titrated?Explanation / Answer
a. Titration reaction
AgNO3 + OCN- --------> AgOCN + NO3-
Indicator reaction
AgNO3(aq) + e- -------> Ag(s) + NO3-(aq)
b. Initial concentration of the second anion.
moles of AgNO3 = Molarity x volume
= 0.1021 M x 0.030 L
= 0.003 moles
Sonce the reaction would be 1 : 1 equivalent, moles of secodn anion would be 0.003 moles
Total volume = 50 + 30
= 80 mL
= 0.080 L
concentration in Molarity of second anion = moles / L
= 0.003 / 0.080
= 0.038 M
c. Based on the list given, the identitiy of the second anion titrated would be OCN-
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