I have done a titration to find the vitamin c concentration in cabbage. This turned out to be 1.25x10^-4 moles per litre. However, I am required to find the concentration in mg/100g. Can I convert moles per litre to mg/100g or is there another way to calculate it. Please help!!

If you have mols/1000 mL, then just divide mols by 10 to obtain mols/100 mL. Since the concentration is so small, the density of the solution will be essentially 1.00; therefore, 100 mL will have a mass of 100 g. Now take the mols and convert to grams. Remember g = mols x molar mass.