Question

I need help with part C.

Some people have an allergic reaction to the food preservative sulfite (SO_3^2-), which can be measured by instrumental methods^37 or by a redox titration: To 50.0 mL of wine were added 5.00 mL of solution containing (0.804 3 g KIO_3 + 6.0 g KI)/100 mL. Acidification with 1.0 mL of 6.0 M H_2SO_4 quantitatively converted IO_3^- into I_3^-. The I_3^- reacted with SO_3^2- to generate SO_4^2-, leaving excess I_3^- in solution. The excess I_3^- required 12.86 mL of 0.048 18 M Na_2S_2O_3 to reach a starch end point. Write the reaction that occurs when H_2SO_4 is added to KIO_3 + KI and explain why 6.0 g KI were added to the stock solution. Is it necessary to measure out 6.0 g accurately? Is it necessary to measure 1.0 mL of H_2SO_4 accurately? Write a balanced reaction between I_3^- and sulfite. Find the concentration of sulfite in the wine. Express your answer in mol/L and in mg SO_3^2- per liter. t test. Another wine was found to contain 277.7 mg SO_3^2- /L with a standard deviation of plusminus2.2 mg/L for three determinations by the iodi-metric method. A spectrophotometric method gave 273.2 plusminus 2.1 mg/L

Answer 1

tion of iodine. 6-32. Some people have an allergic reaction to the food preserva- ive sulfite (SO3which can be measured by instrumental meth- Blancd quation : so3 2- 13 S04 2-31 ods" or by a redox titration: To 50.0 mL of wine were added 5.00 mL of solution containing (0.804 3 g KIO 6.0 g KIM100 mL. Acidi ication with 1.0 m of 6.0 M H2SO4 quantitatively converted IO inlo l. The Ij reacted with So to generate SO leaving excess , in solution. The excess Ij required 12.86 mL of 0.048 18 M moles of Na2S203 used to titrate excess 13- 2 NaS,0, to reach a starch end point. al Write the reaction that occurs when H2SO, is added to KIO, + KI and explain why 6.0 g KI were added to the stock solution. is it necessary to measure out 6.0 g accurately? Is it necessary to mea- sure 1.0 mL of H2SO, accurately? b) Write a balanced reaction between Ij and sulfite ICI Find the concentration of sulfite in the wine. Express your answer in mol/L and in mg SOj per liter. d)rtest. Another wine was found to contain 277.7 SO L with a andard deviation of +2.2 mg/L for three deterninations by the iodi- metric method. A spectrophotometric method gave 273.2 ± 2.1 mg/L moles ofNa28203 used to titrate excess 13- 0.04818 M x 0.01286 ml 6.2 x 104-4 mols Now calculate the moles of 13- asa follows: moles of13 6.2x 10-4/2 3.1 x 10*-4 mol:s moles of IO3-amount in molar mass -0.8043/214.001 -3.76x 10-3 mols molar mass of KI-166.0028 gmol moles ofI 6166.003 0.036 mols I mole of IO3-reacts with 5 mois of I-, so 3.76 x 10へ4 mois 103. would require = 0.019 mols of I- sinceI- available is excess, IO3-is the iting reagent due to following reasons: agen 1. It completely reacted in the reaction 2. It delees te aou of the pruduct i moles of13- foned 2x3.76 x 10A-4 7.52 x 10-4 ols moles ofI13- reacted with SO3 27.52x 10*-4- 3.1x 10*-44.42 x 10 moles of. SO302-in sample= 4.42 x 10 4 mals 4 mols concentration of SO3 2-in wine 4.42 x 10-4 0.005/0.105-2.10 x 10A-S molL In g/L-2.10 x 105 x 80.0632 1.68 x 10-3 g/L In ng/L- 1.68 x 10 Lx1000 ng/1.0 g 1.68 mgL