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3.16     Three electrolytic cells A,B,C containing solutions of ZnSO_{4}AgNO_{3} and CuSO_{4}, respectively are connected in series. A steady current of 1.5 amperes was passed through them until 1.45 g of silver deposited at the cathode of cell B. How long did the current flow? What mass of copper and zinc were deposited?

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Since the cells are connected in series so the current passing through each cell will be equal.(1.5 A)

Now we are given that 1.45 g of silver is deposited. So firstly we will consider the cell containing silver.

                                                   Ag^+\ +\ e^-\ \rightarrow Ag

Since for deposition of 108 g silver 96487 C charge is required, thus for 1.45 g deposition of silver charge required will be:- 

                                                              = \frac{96487}{108}\times1.45        = 1295.43\ C

Now we can find the time taken by 1.5 A current to deposit 1.45 g silver.

                                                         Time\ taken = \frac{1295.43}{1.5} \approx 864\ sec.

For copper:- 

                                Cu^{+2}\ + 2e^-\ =\ Cu

Since 2F charge will deposit 63.5 g of Cu,  then deposition by 1295.43 C will be:-

                                                                                                 = \frac{63.5}{2\times96487}\times1295.43         = 0.426\ g

 Hence 0.426 g of copper will be deposited.   

 For zinc:-  

                               Zn^{+2}\ +\ 2e^-\ \rightarrow\ Zn

Since 2F charge will deposit 65.4 g of Zn,  then deposition by 1295.43 C will be:-

                                                                                                 = \frac{65.4}{2\times96487}\times1295.43         = 0.439\ g

 Hence 0.439 g of zinc will be deposited.   

Posted by

Devendra Khairwa

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