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This reaction as written has a negative potential.  It will not occur spontaneously.  Instead, it is the reverse process that will readily occur.  To drive a Nonspontaneous redox reaction, a potential greater than the cell potential is applied from an external source.  This process is called electrolysis.

Note- Law of attraction.

The positive ions head towards the negative electrode. Their charge reduces to zero. So the negative electrode is the called the cathode.

The negative ions head towards the positive electrode. Their charge increases to zero (oxidation). So the positive electrode is the called the anode.


2 H2O(l)  -->  O2(g)  +  2H2(g)

Electrolysis of water

2 NaCl(l)  -->  2 Na(l)  +  Cl2(g)

Electrolysis of salt


Past Regents Questions

Jan 2009-23 Which statement describes electrolysis?
(1) Chemical energy is used to produce an electrical change.
(2) Chemical energy is used to produce a thermal change.
(3) Electrical energy is used to produce a chemical change.
(4) Thermal energy is used to produce a chemical change

Aug 2008-45 Given the balanced equation representing a reaction occurring in an electrolytic cell:
2NaCl(l)==> 2Na(l) + Cl2(g)
Where is Na(l) produced in the cell?
(1) at the anode, where oxidation occurs
(2) at the anode, where reduction occurs
(3) at the cathode, where oxidation occurs
(4) at the cathode, where reduction occurs

June 2002-22 Which process requires an external power source?

(1) neutralization      (3) fermentation
(2) synthesis            (4) electrolysis

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