Chemistry Help please! Iodine Clock experiment

Question

Calculate the concentration of KIO3 in the final mixture for each of your dilutions. Remember that the origional KIO3 was 0.200M and that the original dilution, when mixed with 10 mL of solution B, gave a total volume of 20mL in each use.

Answer 1

Original volume + 10 ml of solution B = 20 ml, so original volume must have been 10 mls.

V1M1 = V2M2

V1 = initial volume = 10 ml

M1 = initial concentration = 0.200 M

V2 = final volume = 20 ml

M2 = final concentration = ?

(10 ml)(0.200 M) = (20 ml)(x M)

x = 0.100 M KIO3

Answer 2

When doing dilution calcs, track solute (the stuff dissolved) and the solvent (water) separately.

Molarity is mols-solute per liter-solution. Track mols-solute. first 0.2mol-solute/liter-solution x mL-solution = mol-solute.

If you add so many mL of solvent to dilute the solte, the liter-solution is now larger = mL-solvent + original mL-solution x 1000. But mols-solute is the same. Thus, mols-solute/liter-solution is smaller, ergo, diluted.

Track separately. No shortcuts.