4.6 CHAPTER 4. ELECTROCHEMICAL REACTIONS
- The following equation can be deduced from the table of standardelectrode
potentials:
2Cr 2 O^27 −(aq) + 16H+(aq)→ 4Cr3+(aq) + 3O 2 (g) + 8H 2 O(l) (E^0 = +0.10V)This equation implies that an acidified solution of aqueous potassium dichromate
(orange) should react toform Cr3+(green). Yet aqueous laboratory solutions of
potassium dichromate remain orange for years. Which ONE of the following best
explains this?(a) Laboratory solutionsof aqueous potassium dichromate are not acidified(b) The E^0 value for this reaction isonly +0.10V(c) The activation energy is too low(d) The reaction is non-spontaneous(IEB Paper 2, 2002)- Sulphur dioxide gascan be prepared in thelaboratory by heating amixture of
copper turnings and concentrated sulphuric acidin a suitable flask.
(a) Derive a balanced ionic equation for this reaction using the half-reactions
that take place.(b) Give the E^0 value for the overall reaction.(c) Explain why it is necessary to heat the reaction mixture.(d) The sulphur dioxidegas is now bubbled through an aqueous solution of
potassium dichromate.Describe and explain what changes occur during
this process.(IEB Paper 2, 2002)More practice video solutions or help at http://www.everythingscience.co.za(1.) 01r4 (2.) 01r5 (3.) 01r6 (4.) 01r7 (5.) 01r84.6 Applications of electrochemistry
ESCCA
Electrochemistry has a number of different uses,particularly in industry.We are going
to look at a few examples.