posted by .

Please check my answers.

1. Using the equations,
IO3- +5I- + 6H+ -> 3I2 + 3H2O
C6H8O6 + I2 -> C6H6O6 + 2I- + 2H+

how many equivalents of IO3- are required to produce enough I2 to oxidize one equivalent of ascorbic acid?

Answer: 1IO3- <-> 3I2 <-> 3C6H8O6
1/3 equivalents of IO3-

2. A 10 g sample of no name grape drink mix is diluted to 250 mL. 50 mL of grape drink is titrated with 35 mL of 0.005 M KIO3 solution.

a) How many moles of ascorbic acid are present in 50 mL of the grape solution?

0.005 mol/L KIO3 x 0.035 L KIO3 =
1.75 x 10^-4 mol KIO3

1.75 x 10^-4 mol KIO3 x (3 mol I2/1 mol KIO3) = 5.25 x 10^-4 mol I2.

3 KIO3 <-> 3 C6H8O6, so same amount of moles of C6H8O6.

b) What is the percent by mass of ascorbic acid in a package of grape drink mix?

5.25 x 10^-4 mol C6H8O6 x 176.124 g/mol C6H8O6 = 0.092 g C6H8O6

But this is grams in 50 mL of solution - we have 250 mL throughout which the ascorbic acid is distributed. So 0.092 g x 5 = 0.462 g C6H8O6 within 250 mL solution.

0.462 g/10.00 g x 100 = 4.62%

c) If there are 8 servings per package, calculate the %RDA of vitamin C in each serving of no name grape mix. Formula: (mg ascorbic acid/serving)/75 mg

(462 mg C6H8O6/8)/75 mg
= 0.77 % RDA

Thanks for your help!

  • Chemistry -

    I think all of your work is good except for 1. I believe the answer is 1/6 mol IO3^- = 1 equivalent ascorbic acid.
    1 mole IO3^- = 3moles I2
    3 moles ascorbic acid = 3 moles I2; therefore, 1 mole IO3^- = 3 moles I2
    In the next step,
    C6H8O6 + I2 ==> C6H6O2 +2H^+ + 2I^-
    So this step is 1 mol C6H8O = 1 mol I2 but
    2 equivalents C6H8O6 = 2 equivalents I2 (since I2 goes from 0 to -2 for 1 mole, that is 2e change for 1 mol, the equivalent weight I2 is 1/2 molar mass pr 2 equivalents. Therefore,
    1/3 mol IO3^- = 1 mole I2 = 2 equivalents I2 and
    1/6 mol IO3^- = 1 equivalent I2.
    1/6 mol IO3^- = 1 equivalent ascprbic acid. You can check that out in your percent, which you did with moles and the 4.62% is correct.
    If we do that with equivalents (and milliequivalents) we should get the same answer. m.e. = # milliequivalents and m.e.w. = milliequivalent weight.
    So mL = 35 mL
    Normality = 0.005*6 (since there are 6 equivalents in 1 mole IO3^-).
    m.e.w. ascorbic acid = molar mass/2 = 176.124/2000 =0.088062
    (mL x N x m.e.w./mass sample)*100 =
    35.0mL x 0.03N x 0.088062g/2g sample)*100 = 4.62%

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Chemistry

    Given these chemical reactions: Ca^(2+)(aq) + 2IO3^(-)(aq) → Ca(IO3)2(s) Ca(NO3)2·4H2O(s) → Ca^(2+)(aq) + 2NO3^(-)(aq) + 4H2O(l) KIO3(s) → K^(+)(aq) + IO3(-)(aq) Calculate the masses of Ca(NO3)2·4H2O(s) and KIO3(s) …
  2. science- chemistry

    what is the rate of reaction, if rate of consumption of iodide is 2.130x10^-5?
  3. Chemistry(Please check)

    . Ksp for Fe(IO3)3 is 10-14. Two solutions, one being iron(III) nitrate and the other being sodium iodate, were mixed. At the instant of mixing, [Fe3+] = 10-4M and [IO3-] = 10-5M. What happens?
  4. Chemistry

    For the reaction IO3– + 5I– + 6H+ 3I2 + 3H2O the rate of disappearance of I– at a particular time and concentration is 2.8 x 10-3 M s-1. What is the rate of appearance of I2 in molarity per second?
  5. Chemistry

    What mass of KIO3 is needed to convert the copper in 0.200g of CuSO4.H2O to Cu(IO3)2?
  6. Chemistry

    Calculate the concentration of IO3– in a 9.23 mM Pb(NO3)2 solution saturated with Pb(IO3)2. The Ksp of Pb(IO3)2 is 2.5 × 10-13. Assume that Pb(IO3)2 is a negligible source of Pb2 compared to Pb(NO3)2.
  7. college chem

    Determine the rate of consumption of I− if the initial concentration of IO3− was 0.6634 M and decreased to 0.5745 M after 0.3964 hours. Use the reaction below. IO3− + 5I− + 6H+ ↔ 3I2 + 3H2O
  8. Chemistry

    Hello, I would greatly appreciate some help with the following problem, as I'm not sure how to proceed. I'm trying to find solubility (Ksp) of Cu(IO3)2 from titration experiment. The following equations were provided: Cu(IO3)2 --> …
  9. chem

    Calculate the concentration of IO3– in a 4.73 mM Pb(NO3)2 solution saturated with Pb(IO3)2. The Ksp of Pb(IO3)2 is 2.5 × 10-13. Assume that Pb(IO3)2 is a negligible source of Pb2 compared to Pb(NO3)2.
  10. chemistry

    How to find the moles of IO3- reacted when you have .00001mol of 10mL HSO3-?

More Similar Questions