DM.a-n - Developing Metals | DM1-6 |
DM.Q Exam questions from past papers
● Pt electrode for Fe3+ / Fe2+ half cell (1)
● In Fe3+ / Fe2+ (1)
● Cu electrode in Cu2+ (1)
● Salt bridge labelled and in solutions (1)
● Conditions: 1moldm-3 and 298K / 25C (1)
● 0.43V (1)
If a half cell was VO2+ + 2H+ + e- -> VO2+ + H2O then a
label for H+ would also be required
Complete the diagram below that shows the Ecell
value (5)?
Calculate the Ecell value (1) ?
● Faster in sea water as more dissolved ions makes it
Suggest why rusting takes place faster in a better conductor
seawater than in rainwater?
,The students wants to use this electrode to
measure the standard electrode potential of a
Fe/Fe2+ half cell
Give instructions on how to do this justifying the
uses of the pieces of apparatus you name.
[You may add to the diagram to illustrate ur Set up:
answer] ● Make sure reading on voltmeter is positive
● Electrode/half cell connected to positive terminal of
voltmeter is the positive electrode
● From knowing
Description of the apparatus used and why:
● High resistance voltmeter so negligible current is
taken (so conc’s of ions stay the same)
● Salt bridge to keep the charge in each half cell
constant
● Draw complete electrochemical cell ;)
● Fe(s) electrode
Conditions/Conc
● 298K/25C
● 1moldm-3 in Fe/Fe2+
DM.a - Formulae, equations & amount of substance | DM1 |
What acid should be used for manganate Excess dilute sulfuric acid as other acids can set up
redox titrations? Why? alternative redox reactions (leading to inaccurate titres) as
seen below
, Why is an indicator not required for a As manganate (MnO4-) is pink (the only coloured reagent)
manganate sulfuric acid redox titration and and so when it's reduced it produces Mn2+ which is
its colour change? colourless and the endpoint is when the pink reappears
MnO4- (aq) + 8H+ (aq) + 5Fe2+ -> Mn2+ (aq) + 4H2O (l) + 5Fe3+
(aq)
Why must EXCESS sulfuric acid be used in a Otherwise, the solution won’t be acidic enough and MnO2
manganate sulfuric acid redox titration will be produced instead of Mn2+
Remember MnO4- (aq) + 8H+ (aq) + 5Fe2+ (aq) -> Mn2+
(aq) + 4H2O (l) + 5Fe3+ (aq)
DM.Q Exam questions from past papers
● Pt electrode for Fe3+ / Fe2+ half cell (1)
● In Fe3+ / Fe2+ (1)
● Cu electrode in Cu2+ (1)
● Salt bridge labelled and in solutions (1)
● Conditions: 1moldm-3 and 298K / 25C (1)
● 0.43V (1)
If a half cell was VO2+ + 2H+ + e- -> VO2+ + H2O then a
label for H+ would also be required
Complete the diagram below that shows the Ecell
value (5)?
Calculate the Ecell value (1) ?
● Faster in sea water as more dissolved ions makes it
Suggest why rusting takes place faster in a better conductor
seawater than in rainwater?
,The students wants to use this electrode to
measure the standard electrode potential of a
Fe/Fe2+ half cell
Give instructions on how to do this justifying the
uses of the pieces of apparatus you name.
[You may add to the diagram to illustrate ur Set up:
answer] ● Make sure reading on voltmeter is positive
● Electrode/half cell connected to positive terminal of
voltmeter is the positive electrode
● From knowing
Description of the apparatus used and why:
● High resistance voltmeter so negligible current is
taken (so conc’s of ions stay the same)
● Salt bridge to keep the charge in each half cell
constant
● Draw complete electrochemical cell ;)
● Fe(s) electrode
Conditions/Conc
● 298K/25C
● 1moldm-3 in Fe/Fe2+
DM.a - Formulae, equations & amount of substance | DM1 |
What acid should be used for manganate Excess dilute sulfuric acid as other acids can set up
redox titrations? Why? alternative redox reactions (leading to inaccurate titres) as
seen below
, Why is an indicator not required for a As manganate (MnO4-) is pink (the only coloured reagent)
manganate sulfuric acid redox titration and and so when it's reduced it produces Mn2+ which is
its colour change? colourless and the endpoint is when the pink reappears
MnO4- (aq) + 8H+ (aq) + 5Fe2+ -> Mn2+ (aq) + 4H2O (l) + 5Fe3+
(aq)
Why must EXCESS sulfuric acid be used in a Otherwise, the solution won’t be acidic enough and MnO2
manganate sulfuric acid redox titration will be produced instead of Mn2+
Remember MnO4- (aq) + 8H+ (aq) + 5Fe2+ (aq) -> Mn2+
(aq) + 4H2O (l) + 5Fe3+ (aq)
