Transition Metals - Titrations of Fe2+ ans C2O4^2- with MnO4^- Flashcards
what colour is MnO4^-
Purple
is the titration of Fe2+ with MnO4^- self indicating
Yes cos of the significant colour change of the MnO4^- from purple to colourless.
give the equation for the reeaction of the titration of Fe2+ with MnO4^-
MnO4^-(aq) + 8H^+(aq) + 5Fe^2+ (aq) -> Mn^2+ (aq) + 4H2O (l) + 5Fe^3+ (aq)
why is chossing the correct acid for manganate titrations so important
cos the acid is needed to supply the 8H+ ions. some acids are not suitable as they set up different redox reactions and result in titration readings being inaacurate.
what is the only acid to use in manganate titrations
sufficient volumes of dilute sulfuric acid.
what impact does insuffiecient volumes of dilute sulfuric acid have on the titrations
Insuffecient volumes of dilute HsSO4 results in the solution not being acidic enough and MnO2 being produced instead of Mn2+
MnO4-(aq) + 4H+(aq) + 3e- -> MnO2(s) + 2H2O
- the brown MnO2 will mask the colour change and lead to a greater (inaccurate) volume of manganate being used in the titration.
what effect does using a weak acid like ehtanoic acid in the titrations
the same effect as using insuffiecient volume H2SO4 as it can’t supply enough hydrogen ions needed.
why can’t HCl be used in the titration
cos the Cl- ions would be oxidised to Cl2 by MnO4^-. this is becuase the electrode potential value of MnO4- is greater than the value of Cl2. this would lead to a greater volume of manganate being used and poisonous Cl2 will be produced.
why can’t nitric acid be used
because it is an oxidising agent and oxidises Fe2+ to Fe3+ as it has a higher electrode potential value. results in a smaller volue of manganate being used.
whats the equation of the titration of ethandioate (C2O4^2-)
2MnO4^-(aq) + 16H^+(aq) + 5C2O4^2-(aq) -> 10CO2(g) + 2Mn2+(aq) + 8H2O(l)
why is the titration between ethandioate (C2O4^2-) an MnO4^- slow initially and what can be done to overcome it.
it is slow initially cos the reaction is happening bwtween 2 negative ions. to overcome this the conical flask can be heated to 60 degrees to speed up the initial reaction.
how many moles of MnO4- are needed to react with both the Fe2+ and the C2O42- in iron (II) ethanedioate.
3 moles in total to react with 5 moles of FeC2O4
- 2 moles to react with the C2O4-
- and 1 mole to react woth Fe2+
whats the overall equation of the titration of iron (ii) ethandioate with manganate.
3MnO4-(aq) + 24H+(aq) + 5FeC2O4 -> 10CO2 + 3Mn2+ (aq) + 5Fe3+ + 12H2O
