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Vanadium and Oxidation States watch

1. I have been having some real difficulties with this question, it must have been forged with the depths of Mordor:

The Question is here

I know:

Moles V2+ = 25.0 x 0.100 / 1000 = 0.0025 mols
Moles MnO4– = 30.0 x 0.0500 / 1000 = 0.00150 mols

What next
2. (Original post by qazwsxedc)
I have been having some real difficulties with this question, it must have been forged with the depths of Mordor:

The Question is here

I know:

Moles V2+ = 25.0 x 0.100 / 1000 = 0.0025 mols
Moles MnO4– = 30.0 x 0.0500 / 1000 = 0.00150 mols

What next
It is the V5+ that has a mole of 0.0025 mol.( i think)

From the equation given, mole of electrons consumed = 5 x mol of MnO4-
= 5 x 0.0015 = 0.0075 mol

mol of electron consumed in second reaction = mol of electron produced in the first reaction, remember first reaction is an oxidation reaction, oxidation means lose electrons.

therefore you know that mol of electron lost in first reaction = 0.0075
and you know mol of V5+ reacted = 0.0025, so it must mean that 3 electrons have been lost in the first reaction.

When V2+ lose three electrons, it gets oxidised to V5+ hence shown.
3. (Original post by shengoc)
It is the V5+ that has a mole of 0.0025 mol.( i think)

From the equation given, mole of electrons consumed = 5 x mol of MnO4-
= 5 x 0.0015 = 0.0075 mol

mol of electron consumed in second reaction = mol of electron produced in the first reaction, remember first reaction is an oxidation reaction, oxidation means lose electrons.

therefore you know that mol of electron lost in first reaction = 0.0075
and you know mol of V5+ reacted = 0.0025, so it must mean that 3 electrons have been lost in the first reaction.

When V2+ lose three electrons, it gets oxidised to V5+ hence shown.
Gosh, so complicated - but you make it seem very straight forward - thank you shengoc

Much Appreciated!
4. (Original post by qazwsxedc)
Gosh, so complicated - but you make it seem very straight forward - thank you shengoc

Much Appreciated!
No worries, since it is a show that question, just try to make sense of stoichiometry and think about what is reacted and what it produced. It served me well, and i think it could serve you well, too. All the best.

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