Electrochem_Part1.pdf - ELECTROCHEMISTRY(Refer to Chapter...

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59 ELECTROCHEMISTRY (Refer to Chapter 19 – Electrochemistry ) OXIDATION __________ of electrons by an atom, molecule, ion, etc . REDUCTION __________ of electrons by an atom, molecule, ion, etc . e.g. , 2Na (s) + Cl 2 (g) 2NaCl (s) Here the Na metal is _______________ to Na + (1 electron lost per sodium atom) and Cl 2 is _______________ to 2Cl (1 electron gained per chlorine atom). Aside: You may have heard the phrase: " LEO the lion says GER " where LEO stands for "Loss of Electrons is Oxidation" and GER stands for "Gain of Electrons is Reduction". OR OIL RIG where "OIL" stands for "Oxidation Is Loss (of electrons)" and "RIG" stands for "Reduction Is Gain (of electrons)" Question : All the following are oxidation-reduction reactions EXCEPT A. H 2 ( g ) + F 2 ( g ) 2HF ( g ) . B. Mg 3 N 2 ( s ) + 6H 2 O ( l ) 3Mg(OH) 2 ( s ) + 2NH 3 ( g ) . C. 2K ( s ) + 2H 2 O ( l ) 2KOH ( aq ) + H 2 ( g ) . D. 6Li ( s ) + N 2 ( g ) 2Li 3 N ( s ) . E. Ca ( s ) + H 2 ( g ) CaH 2 ( s ) . Oxidation– Reduction or REDOX Reactions Reactions which involve _________ GAIN (reduction) and LOSS (oxidation) of electrons. It is convenient to think of the overall REDOX reaction as two individual HALF-rxns , namely an oxidation half– reaction and a reduction half– reaction, i.e. , 2Na (s) 2Na + (aq) + 2e (oxidation ½ – reaction) + Cl 2 (g) + 2e 2Cl (aq) (reduction ½– reaction) 2Na (s) + Cl 2 (g) 2NaCl (aq) Question : In the following, which species is oxidized? 3Ag 2 S ( s ) + 8H + ( aq ) + 2NO 3 ( aq ) 6Ag + ( aq ) + 3S ( s ) + 2NO ( g ) + 4H 2 O ( l ) A. NO 3 B. Ag 2 S C. NO D. H + E. Ag + NOTES:
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