an old tablet of vitamin c weighed 1.022 g. It was dissolved in 500 mL water, and a 25.0 mL aliquot of this solution required 22.6 mL of .005 M I2 solution to oxidize it. Calculate the mg vitamin C in the tablet.
To calculate the mg of vitamin C in the tablet, we need to follow these steps:
Step 1: Calculate the number of moles of I2 used.
We know that the volume of the I2 solution used is 22.6 mL and the molarity (M) is 0.005 M. To calculate the number of moles (n) of I2 used, we can use the formula:
n = M x V
= 0.005 mol/L x 0.0226 L
Step 2: Calculate the number of moles of vitamin C.
The balanced chemical equation between I2 and vitamin C (ascorbic acid) is:
C6H8O6 + I2 → C6H6O6 + 2HI
From the equation, we can see that 1 mole of vitamin C reacts with 1 mole of I2. So, the number of moles of vitamin C in the aliquot solution is equal to the number of moles of I2 used.
Step 3: Calculate the mg of vitamin C.
We can use the molecular weight of vitamin C (ascorbic acid) to convert the moles of vitamin C to milligrams.
The molecular weight of vitamin C is 176.12 g/mol.
mg of vitamin C = moles of vitamin C x molecular weight
= n x 176.12 g/mol
By following these steps, we can calculate the mg of vitamin C in the tablet.
C6H8O6 + I2 + H2O → C6H6O6 + 2I^- + 2H^+
mols I2 = M x L = ?
mols vit C = mols I2 since the ratio is 1:1 in the balanced equation.
g vit C in the titrated portion = mols x molar mass. Convert to mg vit C the multiply by 500/25 to give mg vitamin C in the tablet.