Gen chem ques

[predentgal]

During a titration it was determined that
30.00 mL of a 0.100 M Ce4+ solution was
required to react completely with 20.00
mL of a 0.150 M Fe2+ solution. Which
one of the following reactions occurred?
A. Ce4+ + 3Fe2+ + H2O ->3Fe3+
+ CeO- + 2H+
B. 2Ce4+ + Fe2+-> Fe4+ + 2Ce3+
C. Ce4+ + Fe2+-> Fe3+ + Ce3+
D. Ce4+ + 2Fe2+-> 2Fe3+ + Ce2+
E. Ce4+ + 2Fe2+ ->2Fe4+ + Cs2+
+ 2e

Totally lost wit this question.. Can anyone explain?

Answer is C​

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[UndergradGuy7]

Find out moles of ce and moles of fe.
Moles of ce is 0.030 l * 0.1 = 0.003 moles
Moles of fe is 0.020 * 0.150 = 0.003 moles

So they react in a 1 to 1 ratio. . Ce4+ + Fe2+-> Fe3+ + Ce3+ is the only one where ce4+ and fe2+ are one to one ratio. One electron is moved.

 

[predentgal]

So the different charges of the ions have nothing to do with what the question is asking for? Only the moles?

 

[UndergradGuy7]

So the different charges of the ions have nothing to do with what the question is asking for? Only the moles?

Well in this problem it is simplified and we can only look at moles.


See post 12 here if you want to know more http://forums.studentdoctor.net/showthread.php?t=419317

So if the equations were not balanced then you would have to look at the oxidation state changes and see that the electrons in ce and fe both change in a 1 to 1 ratio (1 electron given off and 1 accepted by the other).

This is kind of like acids some can donate 1H, 2H etc... (normality).