I dont quite understand how to find out if it's capable of reducing/oxidizing. My understanding is we check each potential and identify which is reduce = highest potential, oxidize = lowest potential.

Question

These are my predictions:
yes
Is Fe2+(aq) capable of reducing VO2+(aq)?

yes
Is Sn metal capable of reducing Fe3+(aq) to Fe2+(aq)?

no
Is H2(g) capable of reducing Ni2+(aq)?

no
Is Cr3+(aq) capable of oxidizing Fe2+(aq)?

yes
Is Fe2+(aq) capable of reducing Sn2+(aq) to Sn metal?

no
Is Fe2+(aq) capable of reducing Cr3+(aq) to Cr2+(aq)?

Answer 1

I do them this way. It would have been helpful for you to include how you came to the conclusions you did AS WELL AS to list the Eo values you looked up. Here is one I've done for you.
Is Fe2+(aq) capable of reducing Sn2+(aq) to Sn metal?
If Sn2+ + 2e ===> Sn (a reduction) then you know
Fe2+ ==> Fe3+ + e because that is an oxidation. So look up the Eo
potentials. For Sn2+ +2e ==> Sn(s) I find Eo red = -0.14
..................For Fe^2+ ==> Fe^3+ + e I find Eo ox = -0.77 (note I looked up the Fe3+ + e ==> Fe2+ to get Eo red of 0.77 then changed the sign.
Now add them together but DON'T multiply the E values by anything.
Sn2+ +2e ==> Sn(s) Eo red = -0.14
Fe^2+ ==> Fe^3+ + e Eoox = -0.77
Sn2+ + 2e + 2Fe2+ ==> Sn(s) + 2Fe^3+ + 2e Eo cell = -0.14 + (-0.77) = -0.91 v for the cell. This cell will NOT go spontaneously so Sn^2+ will NOT reduce the Fe^2+ . You must obtain a + cell value for the cell to work. I find it easy to add the Ered value to the Eo oxd value. If you get a + E value you know the reaction is spontaneous. If you get a - E value you know the reaction is not spontaneous. You know of course to make sure that one half rxn must have electrons on one side and the other half reaction must have electrons on the opposite side. Also, to make the equation accurate you must multiply the half reactions to make the electrons on one side equal to the number on the other side; however, you do NOT multiply the E values. Hope this helps.