CHAPTER 4. ELECTROCHEMICAL REACTIONS 4.6
(IEB Paper 2, 2005)
- The following reaction takes place in an electrochemical cell:
Cu (s) + 2AgNO 3 (aq)→ Cu(NO 3 ) 2 (aq) + 2Ag (s)
(a) Give an equation forthe oxidation half reaction.
(b) Which metal is usedas the anode?
(c) Determine the emf of the cell under standardconditions.
(IEB Paper 2, 2003)
- The nickel-cadmium(NiCad) battery is smalland light and is made in
a sealed unit. It is used in portable appliances such as calculators and
electric razors. The following two half reactions occur when electrical
energy is produced by the cell.
Half reaction 1: Cd(s) + 2OH−(aq)→ Cd(OH) 2 (s) + 2e−
Half reaction 2: NiO(OH)(s) + H 2 O(l) + e−→ Ni(OH) 2 (s) + OH−(aq)
(a) Which half reaction(1 or 2) occurs at the anode? Give a reason
for your answer.
(b) Which substance isoxidised?
(c) Derive a balanced ionic equation for the overall cell reaction for
the discharging process.
(d) Use your result above to state in which direction the cell reaction
will proceed (forward orreverse) when the cell isbeing charged.
(IEB Paper 2, 2001)
- An electrochemicalcell is constructed by placing a lead rod in a
porous pot containinga solution of lead nitrate (see sketch). The
porous pot is then placed in a large aluminiumcontainer filled with
a solution of aluminiumsulphate. The lead rodis then connected to
the aluminium container by a copper wire and voltmeter as shown.
V
copper wire
Pb(NO 3 ) 2 aluminium container
(aq)
Al 2 (SO 4 ) 3 (aq)
porous pot
lead rod
(a) Define the term reduction.
(b) In which direction do electrons flow in thecopper wire? (Al to
Pb or Pb to Al)
(c) Write balanced equations for the reactions that take place at...
i. the anode
