CHAPTER 4. ELECTROCHEMICAL REACTIONS 4.4
Exercise 4 - 6
- An electrochemical cell is made up of a copper electrode in contact with a copper
nitrate solution and an electrode made of an unknown metal M in contact with a
solution of MNO 3. A salt bridge containing a KNO 3 solution joins the two half
cells. A voltmeter is connected across the electrodes. Under standard conditions
the reading on the voltmeter is 0.46V.
V
Cu Salt bridge (KNO 3 )Cu(NO 3 ) 2 (aq) MNO 3 (aq)M
The reaction in the copper half cell is given by:
Cu→ Cu2++ 2e−(a) Write down the standard conditions whichapply to this electrochemical
cell.
(b) Identify the metal M. Show calculations.
(c) Use the standard electrode potentials to write down equations for the:
i. cathode half-reaction
ii. anode half-reaction
iii. overall cell reaction
(d) What is the purposeof the salt bridge?
(e) Explain why a KCl solution would not be suitable for use in the saltbridge
in this cell.(IEB Paper 2, 2004)- Calculate the emf foreach of the following standard electrochemical cells:
(a)
Mg|Mg2+||H+|H 2(b)
Fe|Fe3+||Fe2+|Fe(c)
Cr|Cr2+||Cu2+|Cu