Question

The ion MnOis often used to analyze for the Fe2+ content of an aqueous solution by using the (unbalanced) reaction Mno+Fe2+ + Fe3+ + Mn2+ in acidic solution. A 45.4 mL sample of a solution containing Fe2+ requires 63.3 mL of a 0.0330 M KMnO4 solution for complete reaction. What is the concentration of the Fe2+ in the original solution? A.) 0.0460 M B.) 0.230 M C.) 2.30 x 10-4 M D.) 4.60 x 10-5 M E.) 0.0920 M The molar mass of glucose = 180.2

Answer 1

Answer:

B) 0.230 M

Explanation:

The first step is to balance the reaction between the Ferrous ion and the permanganate ion:

$5~Fe^+^2~+~MnO_4^-^1~+~8H^+~->~5Fe^+^3~+~Mn^+^2~+4H_2O$

Then we have to calculate the moles of $MnO_4^-$:

$M~=~\frac{mol}{L}$

$mol~=~M*L$

$mol~=~0.033~M*0.0633L=~0.002088~mol~MnO_4^-$

Then using the molar ratio we can find the moles of $Fe^+^2$:

$0.002088~mol~MnO_4^-\frac{5~mol~Fe^+^2}{1~mol~MnO_4^-}=0.01044~mol~Fe^+^2$

Finally we can calculate the molarity:

$M=\frac{0.01044~mol~Fe^+^2}{0.0455~L}=0.230~M$