Redox Example 1 - 6 (Fe 2+ Fe 3+ + 1e ) 14 H + + Cr 2 O 7 2...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture Example1: Redox Reaction (Acidic solution) The iron in a 5.675 g sample containing some Fe 2 O 3 is reduced to Fe 2+ . The Fe 2+ is titrated with 12.02 mL of 0.1467 M K 2 Cr 2 O 7 in acid solution. What is the mass of Fe and what is the percentage of Fe in the sample? In almost all cases, the oxygen will have a -2 oxidation state in a compound and the hydrogen will have a +1 oxidation state in a compound. +6 Fe 2+ + Cr 2 O 7 Fe 3+ + Cr 3+ Half reactions: Fe 2+ Fe 3+ + 1e ± (oxidation, reducing agent) +6 Cr 2 O 7 + 6e ± 2 Cr 3+ (reduction, oxidizing agent) Balance the oxygen and hydrogen: (One water molecule for every oxygen needed and H + ions to balance the hydrogen on the other side.) Fe 2+ Fe 3+ + 1e ± 14 H + + Cr 2 O 7 + 6e ± 2 Cr 3+ + 7 H 2 O Balance the charge:
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 6 (Fe 2+ Fe 3+ + 1e ) 14 H + + Cr 2 O 7 2 + 6e 2 Cr 3+ + 7 H 2 O Sum the equations: 6 Fe 2+ 6 Fe 3+ + 6e 14 H + + Cr 2 O 7 2 + 6e 2 Cr 3+ + 7 H 2 O ________________________________________________ 14 H + + Cr 2 O 7 2 + 6 Fe 2+ 6 Fe 3+ + 2 Cr 3+ + 7 H 2 O From the balanced equation, solve the problem: ( ) % 41 . 10 % 100 675 . 5 5909 . % 5909 . 1 85 . 55 Cr 1 6 Cr Cr 1467 . Cr 01202 . 2 2 2 2 7 2 2 2 7 2 2 7 2 2 7 2 = = = + + + + + + + + g g sample in Fe Fe g Fe mol Fe g O mol Fe mol O L O mol O L...
View Full Document

This note was uploaded on 03/17/2010 for the course CH 204 taught by Professor Leytner during the Spring '08 term at University of Texas at Austin.

Ask a homework question - tutors are online