When a clean iron nail is placed in an aqueous solution of copper(II) sulfate, t

Question

When a clean iron nail is placed in an aqueous solution of copper(II) sulfate, the nail becomes coated with a brownish black material. What is the name of the material coating the iron? What are the oxidizing and reducing agents? (Omit states-of-matter in your answer.) oxidizing agent: reducing agent: Can this reaction be made into a voltaic cell? The reaction is, so it be made into a voltaic cell. Write the balanced equation for the reaction. (Use the lowest possible coefficients. Include states-of-matter at 25 degree C and 1 atm in your answer.) Calculate E^o_cell for the process. (Use the table of standard electrode potentials.) E^o_cell = V

Explanation / Answer

Answers, .................

(a).............................Copper

Explanation - It is because of the

.............................................(i) following reaction ( ' Metal displacement reaction ),

...............................................CuSO4(aq) + Fe --------------> Fe SO4 + Cu

..............................................(ii) the reason for this reaction is based on thhe fact that standard reducion potential of copper ion (Cu^2+ ) is lesser than that of iron. therefore Cu^2+ has greater tendency to be reduced .   

(b)

.........................Cu^2+ is an oxidizing agent in the above reaction

[ oxidizing agents are acceptor of electron(s) ]

........................Iron (Fe) in the above reaction is a a reducing agent.

............[ reducing agents are donor of electrons }

......(c)

................Yes , this reaction can be made into a voltaic cell.

....The reaction is -

...............................(i) Reduction (gain of electrons )

..................................... Cu2+ (aq) + 2e -----------> Cu (s)

................................(ii) Oxidation , ( loss of electrons )

.........................................Fe (s)------------------------------> Fe2+   + 2e

........(d)

....................Balanced equation for the reaction -

..............................Fe (s) + Cu2+ (aq)------------> Fe2+ (aq) + Cu (s)

..........(e)

.............................Eo(cell)   = 0.78 V   

....Explantion -

In view of the convention for Oxidation - reduction reaction occuring in Voltaic cell , the half reactions for this cell can be written as

...........................Left electrode : Fe(s) ----------> Fe2+ (aq, , 1M) +2e

...........................Right electrode : Cu2+ (aq, 1M) + 2e------------> Cu(s)

The overall reaction of thecell is the sum of the above two reactions , and we obtain the equation :

................................................Fe (s) + Cu2+ (aq) ---------> Fe2+ (aq) + Cu(s)

..........Using table of standard electrode potential and substituting the values Emf of the cell is calculated as,

........................................Eo(cell) = Eo(right) - Eo(left)

........................................................= [ 0.34 - (- 0.44 ) ] V

........................................................= 0.78 V

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