What is the % Iron in an FeSO4 Sample Based on Titration Data?

[sami23]

Homework Statement

A 0.6500 g sample of an impure FeSO₄ sample is titrated with 33.25 mL of 0.0190 M KMnO₄ to an endpoint. What is the % of iron in the sample?

Homework Equations

KMnO₄ + FeSO₄ --> KSO₄ + FeMnO₄

% Fe = (grams of Fe / grams of sample) * 100%

The Attempt at a Solution

0.03325 L sol'n * (0.0190 M KMnO₄ / 1 L sol'n) = 6.3175*10^-4 M KMnO₄

g FeSO₄ = 6.3175*10^-4 M KMnO₄ * (1 mol FeSO₄ / 1 mol KMnO₄) * (151.903 g FeSO₄ / 1 mol FeSO₄ = 0.09596 g FeSO₄

But now I'm stuck. How do I find g of Fe from 0.09596 g FeSO₄?

% Fe = (grams Fe alone/ 0.6500g FeSO₄)*100% = final answer.

 

[symbolipoint]

What kind of reaction occurs in the analytical titration? Is this an oxidation-reduction reaction? If it is, your reaction statement is wrong.

 

[sami23]

Does that mean it's an acid-base reaction. If it is, then acid + base --> salt + water

 

[symbolipoint]

Sami233, how do you come to the original question that you asked? Are you enrolled in a relevant course now for which you are trying to answer the exercise question?

KMnO4 is not necessarily an acid or base. FeSO4 is not necessarily an acid or base. What do you expect to occur in the reaction between the two? I strongly expect the reaction to be an oxidation-reduction one. Can you write a balanced reaction for this? Can you start with the two separate half-reactions? What kind of endpoint would you expect to observe?

 

[sami23]

2 KMnO4 + FeSO4 --> Fe(MnO4)2 + K2SO4
Fe + H2SO4 --> FeSO4 + H2

 

[sami23]

Endpoint can be determined by:
2MnO4 + 10FeSO4 + 8H2SO4 --> 5Fe(SO4)3 + 2MnSO4 + K2SO4 + 8H2O

0.03325 L * (0.019 M KMnO4/1L) = 6.3175 x 10^-4 mol KMnO4

6.3175 x 10^-4 mol KMnO4 * (10 mol FeSO4/2 mol MnSO4) * (151.9 g FeSO4/1 mol FeSO4) = 0.4798 g FeSO4

0.4798 g FeSO4 * (1 mol FeSO4/151.9 g FeSO4)* (55.847 g Fe/1 mole Fe) = 0.1764 g Fe

% Fe = (0.1764 g Fe/0.6500 g sample)*100% = 27.139%

 

[symbolipoint]

Endpoint can be determined by:
2MnO4 + 10FeSO4 + 8H2SO4 --> 5Fe(SO4)3 + 2MnSO4 + K2SO4 + 8H2O

That reaction is not balanced.