AQA A-LEVEL CHEMISTRY ELECTROCHEMISTRY
QUESTIONS WITH ACCURATE ANSWERS.
What,does,a,metal,have,a,tendency,to,do,when,it,is,dipped,into,a,solution,of,its,ions?,,,ANS,-
,Form,positive,ions,and,go,into,solution.
What,do,metal,ions,have,a,tendency,to,do,when,they,are,in,solution?,,,ANS,-
,To,gain,electrons,and,form,a,metal.
What,is,the,general,rule,about,potentials,and,the,direction,of,the,equation?,,,ANS,-
,The,forwards,reaction,(products),is,the,positive,potential,,whilst,the,backwards,reaction,(reactants),leads
,to,a,more,negative,potential.
What,does,the,position,of,equilibrium,depend,on?,,,ANS,-,Depends,on,the,metal.
-
,Reactive,metals,>,tend,to,form,ions,>,negative,charge,builds,on,metal,>,negative,potential,>,equilibrium,t
o,LEFT.
-,Unreactive,metals,>,positive,charge,on,metal,>,positive,potential,>,equilibrium,to,RIGHT.
What,is,a,half-cell,or,electrode?,,,ANS,-,A,metal,dipping,into,a,solution,of,its,ions.
What,is,used,as,an,electrode,if,there,is,no,solid,metal,involved?,,,ANS,-,A,metal,electrode,-
,typically,platinum,-,is,used,,because,it,is,INERT.
What,are,the,three,types,of,electrode?,,,ANS,-,1.,Metal,electrode:,metal,surrounded,by,its,ions,in,solution.
2.,Gas,electrode:,gas,and,a,solution,of,its,ions.,(Pt,(s),|,H2,(g),|,H+,(aq),
3.,Redox,electrode:,2,different,ions,of,SAME,element,,where,2,types,of,ions,are,present,,eg.,Fe2+,and,Fe3
+.
How,do,you,measure,potential?,,,ANS,-,Cannot,be,measured,directly,>,has,to,be,connected,to,a,half-
cell,of,KNOWN,potential.,The,STANDARD,HYDROGEN,ELECTRODE,(SHE),is,known,as,the,primary,standard.,
2H+,(aq),+,2e-,⇄,H2,(g)
, What,are,the,3,factors,that,can,affect,cell,potential?,,,ANS,-,1.,Temperature
2.,Pressure
3.,Concentration
What,are,the,standard,conditions,for,the,SHE?,,,ANS,-,-,1.00mol,dm^-3,of,ions,involved,in,half-equation.
-,298K,temperature.
-,100kPa,(only,affects,those,which,are,gases).
What,is,a,salt,bridge,and,why,is,it,used?,,,ANS,-
,Typically,a,piece,of,filter,paper,soaked,in,unreactive,ions,(KNO3).,The,salt,bridge,allows,a,pathway,for,diss
olved,ions,to,travel,between,two,solutions,,completing,the,circuit.
Why,is,a,voltmeter,used,in,an,electrochemical,cell?,,,ANS,-
,To,measure,the,EMF,(electromotive,force),i.e.,potential,difference.
True,or,false:,The,position,of,the,redox,equilibrium,changes,with,TIME.,,,ANS,-
,False.,The,position,of,the,redox,equilibrium,changes,with,conditions.,If,a,certain,product/reactant,conc,w
as,changed,,the,eqbm,would,shift,to,oppose,the,change.
What,are,7,rules,with,conventional,notation,of,electrochemical,cells?,,,ANS,-
,1.,|,to,represent,different,states.
2.,||,to,represent,the,salt,bridge.
3.,Most,OXIDISED,species,nearest,to,the,salt,bridge.,
4.,Half-cell,with,MOST,POSITIVE,potential,is,on,the,right-hand,electrode.
5.,The,std.,electrode,is,always,the,LEFT-HAND,electrode.
6.,Oxidation,is,on,the,left,,reduction,is,on,the,right.
7.,R,O,||,O,R.
What,is,the,equation,to,calculate,Ecell?,,,ANS,-,Ecell,=,Eright,-,Eleft.
QUESTIONS WITH ACCURATE ANSWERS.
What,does,a,metal,have,a,tendency,to,do,when,it,is,dipped,into,a,solution,of,its,ions?,,,ANS,-
,Form,positive,ions,and,go,into,solution.
What,do,metal,ions,have,a,tendency,to,do,when,they,are,in,solution?,,,ANS,-
,To,gain,electrons,and,form,a,metal.
What,is,the,general,rule,about,potentials,and,the,direction,of,the,equation?,,,ANS,-
,The,forwards,reaction,(products),is,the,positive,potential,,whilst,the,backwards,reaction,(reactants),leads
,to,a,more,negative,potential.
What,does,the,position,of,equilibrium,depend,on?,,,ANS,-,Depends,on,the,metal.
-
,Reactive,metals,>,tend,to,form,ions,>,negative,charge,builds,on,metal,>,negative,potential,>,equilibrium,t
o,LEFT.
-,Unreactive,metals,>,positive,charge,on,metal,>,positive,potential,>,equilibrium,to,RIGHT.
What,is,a,half-cell,or,electrode?,,,ANS,-,A,metal,dipping,into,a,solution,of,its,ions.
What,is,used,as,an,electrode,if,there,is,no,solid,metal,involved?,,,ANS,-,A,metal,electrode,-
,typically,platinum,-,is,used,,because,it,is,INERT.
What,are,the,three,types,of,electrode?,,,ANS,-,1.,Metal,electrode:,metal,surrounded,by,its,ions,in,solution.
2.,Gas,electrode:,gas,and,a,solution,of,its,ions.,(Pt,(s),|,H2,(g),|,H+,(aq),
3.,Redox,electrode:,2,different,ions,of,SAME,element,,where,2,types,of,ions,are,present,,eg.,Fe2+,and,Fe3
+.
How,do,you,measure,potential?,,,ANS,-,Cannot,be,measured,directly,>,has,to,be,connected,to,a,half-
cell,of,KNOWN,potential.,The,STANDARD,HYDROGEN,ELECTRODE,(SHE),is,known,as,the,primary,standard.,
2H+,(aq),+,2e-,⇄,H2,(g)
, What,are,the,3,factors,that,can,affect,cell,potential?,,,ANS,-,1.,Temperature
2.,Pressure
3.,Concentration
What,are,the,standard,conditions,for,the,SHE?,,,ANS,-,-,1.00mol,dm^-3,of,ions,involved,in,half-equation.
-,298K,temperature.
-,100kPa,(only,affects,those,which,are,gases).
What,is,a,salt,bridge,and,why,is,it,used?,,,ANS,-
,Typically,a,piece,of,filter,paper,soaked,in,unreactive,ions,(KNO3).,The,salt,bridge,allows,a,pathway,for,diss
olved,ions,to,travel,between,two,solutions,,completing,the,circuit.
Why,is,a,voltmeter,used,in,an,electrochemical,cell?,,,ANS,-
,To,measure,the,EMF,(electromotive,force),i.e.,potential,difference.
True,or,false:,The,position,of,the,redox,equilibrium,changes,with,TIME.,,,ANS,-
,False.,The,position,of,the,redox,equilibrium,changes,with,conditions.,If,a,certain,product/reactant,conc,w
as,changed,,the,eqbm,would,shift,to,oppose,the,change.
What,are,7,rules,with,conventional,notation,of,electrochemical,cells?,,,ANS,-
,1.,|,to,represent,different,states.
2.,||,to,represent,the,salt,bridge.
3.,Most,OXIDISED,species,nearest,to,the,salt,bridge.,
4.,Half-cell,with,MOST,POSITIVE,potential,is,on,the,right-hand,electrode.
5.,The,std.,electrode,is,always,the,LEFT-HAND,electrode.
6.,Oxidation,is,on,the,left,,reduction,is,on,the,right.
7.,R,O,||,O,R.
What,is,the,equation,to,calculate,Ecell?,,,ANS,-,Ecell,=,Eright,-,Eleft.
