must know equations - TM

half equation for MnO4-

MnO₄^- + 8H+ + 5e- ——> Mn2+ + 4H₂O

MnO4- (purple) is self indicating = colourless to pink is endpoint

colourless = Mn2+

so when MnO4- just in excess (neutralisation point

Fe half equation

Fe²⁺ —→ Fe3+ +e-

if we don’t have Fe2+ = react Fe element with sulfuric acid to oxidise it

react Fe3+ with Zn to reduce it (Zn must be removed)

full equation for Fe and MnO4-

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

C2O4^2- half-equation

C₂O₄^2- ——> 2CO₂ + 2e-

full equation

2MnO₄^- + 16H+ + 5C₂O₄^2- ——> 2Mn2+ + 8H₂O + 10CO₂

both of the autocatalysis equations for Mn in the C2O4^2-

4Mn²⁺ + MnO₄^- + 8H+ —> 5Mn³⁺ + 4H₂O

2Mn³⁺ + C₂O₄^2- —> 2CO₂ + 2Mn²⁺

what catalyst is used in Haber process

iron catalyst - heterogenous as it is solid and the H₂ N₂ NH₃ (reversible reaction)

only lasts around 5 years before sulfur poisoning occurs

catalyst in Contact process

heterogenous catalyst in manufacture of sulfuric acid

2SO₂ + O₂ <=> 2SO₃

vanadium oxide is the catalyst

V₂O₅ + SO₂ → SO₃ + V₂O₄

V₂O₄ + 1/2O₂ → V₂O₅

homogenous catalyst we need to know

overall equation - all are in aqueous state

S₂O₈^2- + 2I^- → 2SO₄^2- + I₂

high Ea as negatively charged ions repel

two equations

S₂O₈^2- + 2Fe²⁺ → 2SO₄^2- + 2Fe³⁺

low Ea as oppositely charged ions attract

2Fe³⁺ + 2I^- → 2Fe²⁺ + I₂

when using MnO4- in redox titration, what acid should be used

dilute sulfuric acid

MnO4- is oxidising agent

what are the unsuitable acids and why are they unsuitable

hydrochloric - MnO4- would oxidise the Cl- to Cl2 so affect volume needed for titration

conc sulfuric or nitric acid are oxidising agents themselves so affect volume needed for titration

ethanoic acid is weak acid - not enough H+ ions provided