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Predicting spontaneous reactions

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777888:
I don't know how to do some of the questions relating to the spontaneous reactions.

i)Is H2 capable of reducing Ag+? (I say YES, is it right?)

ii)Is Fe(2+) capable of reducing VO(2+)? (How can Fe(2+) be a reducing agent?) ???

iii)Is Fe(2+) capable of reducing Cr(2+) to Cr? (How can Fe(2+) be a reducing agent?)

iv)Is Fe(2+) capable of reducing Cr(3+) to Cr(2+)? (How can Fe(2+) be a reducing agent?)

v)Is it possible for a reagent to redce I2 to I- but not to reduce Cu(2+) to Cu? What RANGE of standard reduction potentials could such a reagent have?
-I say YES, but what is the range? ???

vi)Crystals I2 are added to a solution of NaCl Is this a spontaneous or non-spontaneous reaction?(I don't know if ions/atoms in NaCl are reducing or oxidizing agents. And there's two things in NaCl, how can I know if this is a spontaneous rxn or not?)

Can someone teach me please? THANKS :)

Tetrahedrite:
First of all Fe2+ can act as both an oxidising and reducing agent eg

Fe2+ + 2e- -> Fe(s)  Here it is taking electrons so is an oxidising agent

Fe2+ -> Fe3+ + e- Here it is giving electrons so is a reducing agent

1)the reduction potential for Ag+ is higher than for H+ and it will therefore be reduced.

2)the reduction potention for VO2+ is lower than for Fe2+ therefore no reaction will occur

3) ditto for Cr2+ to Cr

4)ditto for Cr3+ to Cr2+

5) Yes- but s.e.p must fall between 0.54 and 0.34

6)Na+ has an extremely low reduction potential and will therefore not be reduced. Cl2 however has a higher reduction potential than I2 and will therefore be reduced to Cl-

Tetrahedrite:
Apologies, the last statement is wrong, higher reduction potential means it will stay as Cl-

777888:
When predict, do we just looke at the position of the Oxidizing agent and Reduing agent? (ie, Top or bottom) Because the direction of increasing strength of OA and RA are in opposite directions, does that matter?

And for question 6, which one will be reduced? Na+?

Thanks :)

777888:
For #3 and 4,

iii)Is Fe(2+) capable of reducing Cr(2+) to Cr? (How can Fe(2+) be a reducing agent?)

iv)Is Fe(2+) capable of reducing Cr(3+) to Cr(2+)? (How can Fe(2+) be a reducing agent?)

Are the answers "No"?

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