Homework Help: Redox Titration questions!

Posted by Angel on Wednesday, June 11, 2008 at 9:05pm.

Oh goodness, I'm such a pain! I need some help with these! How do I calculate the percentage? How do I start it?

2. Imagine that you ran a similar titration using a different iron sample with 0.02 M KMnO4 as the titrant. Calculate the percent of iron in the sample if the sample weighed 0.67 grams, and the volume of the titrant used was 35.7 mL.

% of iron in sample:

3. Calculate the percent of iron in a 50.0 gram sample containing iron if 45.6 mL of 2.5 M KMnO4 titrant was used.

% of iron in sample:

4. Explain why an overshot endpoint is not a good titration.

The first two questions require me to look at some online interactive lab, but if I know how to do these, I'll be able to do those as well!
Thanks,
-Angel

Redox Titration questions! - DrBob222, Wednesday, June 11, 2008 at 9:42pm
#1.I presume this is titrating Fe(II) to Fe(III).
Write the equation and balance it.
KMnO4 + 5Fe^+2 ==> 5Fe^+3 + Mn+2
You should balance the remainder of the equation.
mols KMnO4 used = M x L = ??

Convert mols KMnO4 to mols Fe by using the coefficients in the balanced equation.
mols Fe = mols KMnO4 x (5 mols Fe^+2/1 mol KMnO4) = ??

Convert mols Fe to grams Fe.
grams = mols Fe x molar mass Fe.

Convert grams Fe to percent.
percent Fe in sample = [grams Fe/mass sample]*100

#2. Worked the same way.
#3. You had the same question last night and I told you to think about it. You WANT to stop at the exact equivalence point. What would undershooting or overshooting the equivalence point mean?
Redox Titration questions! - Angel, Wednesday, June 11, 2008 at 10:16pm
Thank you! Oh, question 4 is fine, I just accidentally copied it with the rest of the questions- it's repeated in this assignment too. Okay, I'll try and get this!
Redox Titration questions! - keke, Friday, April 17, 2009 at 11:47pm
Explain Why an overshot endpoint is not a good titration.?

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