CHEMISTRY QUESTION Suppose you have the following reagents available under stand

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CHEMISTRY QUESTION

Suppose you have the following reagents available under standard conditions. (i.e., P = 1 atm for all gases; t = 25 oC; C = 1 mol L?1 for all aqueous species, including H+ .) Co(s), Ag+ (aq), Cl? (aq), Cr(s), BrO3 ? (aq), I2(s), F? (aq) Consult the standard reduction potentials on the next page and then answer the following questions.

(a) Which is the strongest oxidizing agent?

(b) Which is the strongest reducing agent?

(c) Which of the available reagent(s), if any, will oxidize Zn(s) while leaving Ni(s) unreacted? If none of the available reagents can be used for this purpose, then identify another reagent from the table that could be used. For one of the reagents you’ve identified, write down a balanced chemical equation for the reaction that occurs.

TABLE:

Explanation / Answer

(a) An oxidisinng agent itself gets reduced during a chemical reaction. Hence for a better oxidising agent the standard reduction potential should be positive and higher.

Among the given species Cl-, F- can never be reduced (accept electrons) and will not act as oxidising agent. Now among rest of the species BrO3-(aq) has the highest rediction potential values. Hence BrO3- is the strongest oxidising agent. Hence the answer is BrO3-(aq) (answer)

2BrO3-(aq) + 12 H+(aq) + 10 e- ---- > Br2(l) + 6 H2O, E0(red) = 1.478 V

(b):

A reducing agent itself gets oxidised during a chemical reaction. Hence for a better reducing agent the standard oxidation potential should be higher, or else we can say that the standard reduction potential should be lower.

Among the given species, the oxidation potentia of Cr(s) is the highest or its reduction potential is the lowest.

Hence Cr(s) is the strongest reducing agent. (answer)

Cr(s) --- > Cr2+(aq) + 1e- ,  E0(oxi) = - (- 0.90 V) = + 0.90 V (highest)

(c) Among the given species nobody is able to do this. Hence we need t chose from table

Cr3+(aq), Fe2+(aq), Cd2+(aq), Cr3+(aq),Tl+(aq), and Co2+(aq), having higher reduction potential ( or lower oxidation potential) than Zn(s), can oxidize Zn(s), but are unable to oxidise Ni(s) as they have lower reduction potential than Ni2+(aq),. Hence the answer is any one out of  Cr3+(aq), Fe2+(aq), Cd2+(aq), Cr3+(aq),Tl+(aq), and Co2+(aq).

The balanced chemical reaction for the oxidation of Zn(s) by Co2+(aq), is

Oxidation half: Zn(s) --- > Zn2+(aq) + 2 e- , E0(oxi) = - (- 0.762 V) = + 0.762 V

Reduction half: Co2+(aq) + 2e- --- > Co(s), E0(red) = - 0.282 V

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Overall reaction: Zn(s) + Co2+(aq) ----- > Zn2+(aq) + Co(s),  E0(cell) = + 0.762 V- 0.282 V = + 0.48 V

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