3.2.5.5 variable oxidation states

what do all transition metals have?

a variable oxidation state

give 2 examples of tests where we have seen a variable oxidation state

• testing for aldehydes

• testing for primary + secondary alcohols

describe the two tests that are done to distinguish between aldehydes + ketones

describe the test used to identify primary + secondary alcohols

what is used to reduce vanadium(V) in stages to vanadium(II)?

zinc in acidic solution

what are the 4 oxidation states vanadium has in its compounds?

+5, +4, +3 and +2

describe the method + results of reducing vanadium(V) in stages to vanadium(II)

for the four oxidation states of vanadium, give the species in acidic solution + the colour of solution

describe the method of the re-oxidation of vanadium(II)

how are redox titrations the same + how do they differ with acid base titrations?

• they follow the same theory

• but instead of neutralisation, a redox reaction takes place

give the 3 types of reactions studies regarding redox titrations

what is the oxidising agent in each of these 3 examples?

MnO₄⁻, provided by the reagent acidified potassium manganate KMnO₄

why dont we need an indicator for the redox titrations with MnO₄⁻?

due to the distinctive colour change, MnO₄⁻ is self-indicating

describe + explain the colour change that takes place during these redox titrations

what must the H+ ions be provided by? why?

by H₂SO₄ because if HCl is used the MnO₄⁻ will oxidise the Cl- ions