Johnny needs to figure out how many grams of iron is in his 50mL sample. He titr

Question

Johnny needs to figure out how many grams of iron is in his 50mL sample. He titrates it with 0.00280 M potassium permanganate where it hits the equivalence point when he has added 35.0 mL. How many grams of iron was present in the sample?

            5 Fe+2 + 8H+ + MnO4=1 à 5Fe+3 + Mn+2 + H2O

which element gets oxidized? (for #149)

solve the problem (for #149)

using the internet, google titration of iron with potassium permanganate – using pictures, videos or the web – draw what the experiment would look like – label all instruments and what color is the endpoint? (for # 147)

Explanation / Answer

1) The stoichiometric relationship of permangante to Fe(II):

5Fe2+ + 8H+ + MnO4¯ ---> 5 Fe3+ + Mn2+ + 4 H2O

is five to one.

2) Calculate moles of Fe(II) reacted:

(0.00280 mol / L) (0.0350 L) = 0.000098 mol of MnO4¯

(0.0000980 mol Mn) (5 mol Fe / 1 mol Mn) = 0.000490 mol Fe(II)

3) Determine the TOTAL iron content:

(0.0000980 mol Mn) (5 mol Fe / 1 mol Mn) = 0.000672 mol of total Fe

No. of grams of Fe present = No.of moles * molar mass of Fe = 0.000672 * 55.845 = 0.0375 grams Fe

Fe+2 gets oxidised to Fe3+ by losing an electron.

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