A. If a copper wire is placed in a beaker containing 1 M AgNO3, the clear soluti

Question

A. If a copper wire is placed in a beaker containing 1 M AgNO3, the clear solution is observed to turn blue and a flaky silver color coating appears on the copper wire. Write a net ionic equation to explain this observation.

B. If a silver wire is placed in a beaker containing 1 M Cu(NO3)2, what will happen and why?

C. A student constructs a galvanic cell that has a strip of iron metal immersed in a solution of 0.1M Fe(NO3)2 as one half-cell and a strip of aluminum metal immersed in a solution of 0.1M Al(NO3)3 as the other half-cell. The measured cell potential is less than zero when the positive terminal of the voltmeter is attached to the aluminum strip and the negative terminal is attached to the iron strip.

i. Which half-cell is the anode (Fe or Al)?

ii. Which half-cell is the cathode?

iii.Do the electrons flow from Al to Fe or Fe to Al?

iv. Which metal is more “active” Al or Fe?

Explanation / Answer

A) Copper is more active or above Ag in the electrochemical series, so it can replace Ag from its salt solution.

Cu(s) +2 AgNO3(aq) -------------> Cu(NO3)2 (aq) +2 Ag(s)

Net ionic equation is

Cu(s) + 2Ag+(aq) ----------> Cu+2(aq) + 2Ag(s)

B) If a silver wire is placed in a baeker containing Cu(NO3)2 , no reaction takes place , as silver is less reactive than copper, so it can not replace Cu from its salt solution.

C) In the experiment Al is connected to positive terminal and Fe is to the negative terminal.

That is why the cell potential is negative .

2 Al(NO3)3(aq) +3Fe(s) ----------> 3Fe(NO3)2(aq) +2 Al(s)

This reaction is non- spontaneous as read by the negative value of cell potential.

i)Anode is the electrode where oxidation takes place.

Thus here Fe is the anode (negative electrode) and

ii)Al is the cathode as it is undergoing reduction (positive terminal).

iii) Electrons flowed from Fe to Al

iv) Though Al+3 is reduced to Al in this particular arrangement, the reaction is non-spontaneous.

It shows Al is more reactive than Fe, and the reaction in reverse direction would be spontaneous and Ecell is positive.

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