I need help with this titration problem?

Question

If 26.23 mL of potassium permanganate solution is required to titrate 1.041g of ferrous ammonium sulfate hexahydrate (molar mass of 392.12g) calculate the molarity of the KMnO4 solution

any help would be great

thanks, but how did u get the answer?

i got .017M, but i'm not sure if it's right

there are .0027 moles of the iron complex, and i believe it is a 5:1 ratio, so i got .00045 moles ofKMnO4 and that divided by .02623 L got me .017M

does this sound right, and is the ratio 5:1?

thanks theonlybeldin
i guess i did it right originally, but rounded a little too much

ur answer's perfect thanks a lot

Answer 1

Well, first things first: you need to have the equation for the reaction to be able to get anywhere even close!

# KMnO4 + # Fe(NH4)2(SO4)2▪6H2O ===> ?

You know the MW of the iron complex, and how many grams you have, so you can calculate the number of moles of complex titrated.

Knowing the number of moles you titrated, and the balanced equation for the reaction then, you can calculate how many moles of KMnO4 you used.

Divide the number of moles of KMnO4 by the volume of your titrant (26.23 ml), and convert to moles per liter.

Voila!

Answer 2

What you're performing is a redox titration. In the process, ferrous ion will be oxidized to ferric, while permangante is reduced to manganous ion (Mn2+).

What you need is the balanced equation, or really the ratio between manganese and iron. As manganese is being reduced from +7 to +2, while iron is going from +2 to +3, the ratio is 1:5 (5 irons will be oxidized for every manganese reduced). Thus, you need 5 moles of iron for every mole of manganese.

The number of moles of iron that you have is 1.041g/392.12 g/mol = 0.00265 moles. The number of moles of manganese that you used to tirate it is 1/5 of that, or 0.00053 moles. The molarity of the solution is 0.00053 moles/0.02623 L or 0.0202 M.

Answer 3

i get 1.012123352E-4 M but i might be wrong

Answer 4

i am not to sure what the answer is