the titration of an ascorbic acid requires 18.5 mL of .0105 M KIO3. how many mmol of ascorbic acid were in this sample?
IO3^- + 6H^+ + 5I^- ==> 3I2 + 3H2O
C6H8O6 + I2 ==> C6H6O6 + 2I^- | 2H^+
mmols KIO3 = mL x M = ?
Use the coefficients in the balanced equations to convert mmols KIO3 to mmols ascorbic acid.
?mmol KIO3 x (3 mol I2/1 mol KIO3) x (1 mol I2/1 mol C6H8O6) = ?
To solve this problem, we need to use the concept of stoichiometry from the balanced chemical equation representing the titration reaction. The balanced chemical equation for the reaction between ascorbic acid (C6H8O6) and potassium iodate (KIO3) is:
C6H8O6 + 6H+ + 3IO3- → 3I2 + 6H2O + 2HCO3-
From the balanced equation, we can see that 1 mole of ascorbic acid reacts with 3 moles of KIO3.
Step 1: Calculate the number of moles of KIO3
Given: Volume of KIO3 solution (V) = 18.5 mL = 0.0185 L
Concentration of KIO3 (C) = 0.0105 M
Number of moles of KIO3 = Concentration (C) × Volume (V)
= 0.0105 mol/L × 0.0185 L
= 0.00019425 mol
Step 2: Determine the number of moles of ascorbic acid
From the balanced equation, we know that the ratio of KIO3 to C6H8O6 is 3:1.
Hence, the number of moles of ascorbic acid = 1/3 × moles of KIO3
Number of moles of ascorbic acid = (1/3) × 0.00019425 mol
≈ 6.475 × 10^(-5) mol
Finally, we express the answer in millimoles (mmol):
Number of mmol of ascorbic acid ≈ 6.475 × 10^(-5) mol × (1000 mmol/1 mol)
≈ 64.75 mmol
Therefore, there were approximately 64.75 mmol of ascorbic acid in this sample.