g chem questions

[mrdorky]

Any takes on this? I'm having a hard time taking it step by step and what equations to use to solve this questions... =(


What percentage of iron is present in the ore, if a 1.120 g sample requires 25mL of 0.050M KMnO4 to fully oxidize all of the dissolved Fe2+?

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

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[UndergradGuy7]

Would it just be 0.025 L * 0.050 M = 0.00125 moles of MnO4-
0.00125 moles MnO4- * (5 Fe2+/1MnO4-) = 0.00625 moles of Fe2+
Convert to grams. 0.00625 moles of Fe2+ * (55.8 g/mol) = 0.35 grams of Fe2+
To find the percentage (0.35g / 1.120g) * 100 = 31.3 %

 

[mrdorky]

to UndergradGuy7

Yup that's right...
one of the questions off DAT achiever. I find the chemistry questions very challenging, and annoying.