[polly]

Hi

I am not sure how to calculate the concentration of the following solution:

5ml of 0.1M Ce⁴⁺solution added to 5ml of 0.3M Fe²⁺

This is as far as I got:

Final volume of solution = 10ml

moles of Ce⁴⁺ = 0.1M * 0.005dm³=0.0005mol
thus, concentration = 0.005mol /0.01dm³=0.05M

moles of Fe²⁺ = 0.3M * 0.005dm³=0.0015mol
thus, concentration = 0.0015mol / 0.01dm₃=0.15M

so I have two concentrations (0.05M and 0.15M) ...do I add them together to give me the concentration of whole solution or do I have to do more calculations?

Thank you (in advance) for any ideas

[Borek]

There is reaction taking place.

[kristo]

I think more information is needed.

[Borek]

Depends on what kind of question it is. It can be simple stoichiometry and limiting reagent question, it can be redox equilibrium problem. In the second case you have to check tables to find redox potentials of both systems.

[polly]

Hi thnx 4 reply

Yes it is a redox equilibrium (i think) the question has given me the electrode potential for the reaction Fe³⁺ + e = Fe²⁺ is 0.771V. I have to calculate the potential of a platinum electrode dipping into the solution prepared by adding the 5 ml of 0.1M Ce⁴⁺ to 5ml of 0.30M Fe²⁺.

How do I tackle this question? I thought I had to work out the concentration of the whole solution (for some reason). Do I need to be given the potential for Ce4+ or can I work this out with just the potential of Fe3+

Please help

[Borek]

You need both potentials. Concentrations of Fe³⁺ and Ce³⁺ are connected through reaction stoichiometry.