Page 128 - [B._MURPHY,_C._MURPHY,_B._HATHAWAY]_A_working_meth

112 Chapter 7
I
Eo(Zn2+ I Zn) = -0.76 V and E0(Cu2+ Cu) = + 0.34 V. (R =
8.314 J K-' mol-'; F = 96 500 C mol-').
3. Calculate the equilibrium constant of the following reaction at
300 K:

Sketch the cell that would have this as its cell reaction. If the cell
is short-circuited, indicate clearly the cathode, the anode, the
direction of current, the direction of electrons and the direction
of ion flow, given that E0(Fe3+, Fe2+) = +0.77 V, E"(C12, C1-)
= 1.36 V, R = 8.314 J K-' mol-' and F = 96500 C mol-').
Comment on the value of the equilibrium constant.
4. Calculate the volume (in cm3) of hydrogen gas produced at 25 "C
and 0.65 bar by the electrolysis of water when 0.045 mol of
electrons is supplied. (1 mole of an ideal gas at 1 bar pressure and
298 K occupies 24.8 dm3.)
5. Chlorine gas is produced by the electrolysis of concentrated
aqueous sodium chloride. Give a diagram of this process, in
particular, illustrating the electron flow and the conventional
direction of current. Assuming an anode efficiency of loo%, how
long will it take to produce 0.0025 g of chlorine, in a cell
operating at 760 PA? (F= 96 500 C mol- and molar mass (M) of
CI= 35.453 g mol- ' .)
6. The same quantity of electricity that caused the deposition of
10.2 g of Ag from an AgN03 solution caused the discharge of
6.1 1 g of Au when passed through a solution containing gold
cations of unknown charge, Au"+. Determine m, given that the
molar masses (M) of Ag and Au are 107.87 and 196.97 g mol- '
respectively, and F = 96 500 C mol- '.