Question

For the reaction, shown below, determine which statements are True and which are False.

3Fe(s) + Cr₂O₇^2-(aq) +14H⁺(aq) → 3Fe²⁺(aq) + 2Cr³⁺(aq) + 7H₂O(l)       ξ^o=1.77V

True False  The oxidation state of chromium in dichromate is +6.
True False  The oxidizing agent is Cr³⁺ (aq)
True False  The reducing agent is Cr³⁺ (aq)
True False  The iron half-reaction takes place in an acidic solution.
True False  The lowest oxidation state for hydrogen in this reaction is 0
True False  The oxidation state of oxygen changes from -2 to 0.

If necessary, separate this into two half reactions to determine the oxidizing and reducing agents. Oxidation states can be calculated by remembering that oxygen usually has an oxidation state of 2-, except in O=O or O-O bonds. Hydrogen usually has an oxidation state of 1+, except in H₂.

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Answer 1

True False  The oxidation state of chromium in dichromate is +6.
Cr2O7 = -2

2Cr + 7(-2) = -2

Cr =( -2 + 14 )/(2)

Cr = +6

this is true

True False  The oxidizing agent is Cr3+ (aq)
oxidizing agent must be REDUCED, in this case, Cr is not even in the reagents, so this is FALSE

True False  The reducing agent is Cr3+ (aq)

False, it is in the products, sides, agents are present only on the left

True False  The iron half-reaction takes place in an acidic solution.
Not likely, sinc eFe(s) = Fe+2 + e2- ,requires on O, OH, H2O, H+ balance

True False  The lowest oxidation state for hydrogen in this reaction is 0
false, it is +1, and won't change

True False  The oxidation state of oxygen changes from -2 to 0.

false, since O remains with -2 charge always