March 28, 2024, 04:51:46 AM
Forum Rules: Read This Before Posting


Topic: Titration  (Read 3949 times)

0 Members and 1 Guest are viewing this topic.

Offline badgirllili

  • Very New Member
  • *
  • Posts: 2
  • Mole Snacks: +0/-0
Titration
« on: March 31, 2015, 02:44:05 AM »
Hi. Thanks for viewing my post. :) Please help me answer this problem:

A 0.200 g sample of pyrolusite is analyzed for manganese content as follows: Add 50 mL of a 0.100 M solution of ferrous ammonium sulfate to reduce the MnO2 to Mn^2+. After reduction is complete, the excess ferrous ion is titrated in acid solution with 0.0200 M KMnO4, requiring 15.0 mL. Calculate the percent manganese in the sample as Mn3O4.

The reaction bet. Fe^2+ and MnO4^- is:
5Fe^2+ + MnO4^- + 8H^+ -> 5Fe^3+ + Mn^2+ + 4H2O

The reaction bet. Fe^2+ and MnO2 is:
2Fe^2+ + MnO2 + 4H^+ -> 2Fe^3+ + Mn^2+ + 2H2O

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27637
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Titration
« Reply #1 on: March 31, 2015, 03:34:11 AM »
OK so far.

Hint: this is a back titration.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline badgirllili

  • Very New Member
  • *
  • Posts: 2
  • Mole Snacks: +0/-0
Re: Titration
« Reply #2 on: March 31, 2015, 04:42:47 AM »
OK so far.

Hint: this is a back titration.

My answer is 66.74%. Did I do it right? Thanks!

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27637
  • Mole Snacks: +1799/-410
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Titration
« Reply #3 on: March 31, 2015, 08:09:51 AM »
Looks OK.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Sponsored Links