Contains sulfites
The sulfur dioxide present in white wine is an antioxidant and
antibacterial agent whose mass concentration is limited by law to
210 mg·L–1. When over 10 mg·L–1, the wine
label must indicate "contains sulfites".
A volume V1 = 25.0 mL of previously
discolored white wine is titrated with c = 2.00 × 10–3 mol·L–1
of an iodine aqueous solution. The involved couples are SO42–/SO2
and I2/I–.
The only coloured species is the yellow-brown iodine I2.
a. Identify the analyte and the titrant.
b. Write down the titration reaction equation.
c. Explain how the equivalence point is detected.
d. Detemine the SO2 mass concentration in the wine.
Comment on this result.