Estimation
of Fe+2 by KMnO4 as
primary standard Oxalic acid
Aim of
experiment: Estimation of Fe2+ from supplied
solution by standard KMnO4
Principle:
This process was presented by Mabride in 1912. When oxalic acid acidified with
dil.H2SO4 is titrated with potassium permanganate solution at 60-700C
temperature, an oxidation-reduction reaction takes place between these
substances. The chemical reaction is
When solution of Fe2+ ion acidified with dil. H2SO4
is titrated with potassium permanganate solution at room temperature, an
oxidation-reduction reaction takes place between these substances. The chemical
reaction is
Required materials and solutions:
Burette, pipette (20 ml), 250 ml conical flask, 250ml, volumetric flask, oxalic
acid, potassium permanganate, etc.
Part: I- Preparation of standard
solution of oxalic acid
Weigh
accurately 1.125 g of oxalic acid in a chemical balance (or electronic balance)
and transfer it to a 250 ml volumetric flask. Add 100 ml distilled water and
shake vigorously until all the crystal is dissolved. Add again distilled water
up to the mark of flask and it is labeled as standard oxalic acid solution
Observation:
·
Weight of the Empty Bottle (W1)=
·
Weight of the Bottle + compound (W2)=
·
Weight of the Bottle after transfer of
salt (W3)=
·
Weight of the Oxalic acid (W4) = W2-W3=
Molarity o f the Oxalic acid Solution (m1) = 
Part-II
Estimation of KMnO4 using standard oxalic acid solution
Take
a clean burette and rinse it with potassium permanganate solution, support it
with a burette clamp. Close the stopcock and with the help of a funnel fill
potassium permanganate solution to just above the zero mark. Open the stopcock
to remove any air bubbles in the tip. In a 250 mL conical flask, take 20 mL
oxalic acid by using a graduated pipette and 5mL conc. H2SO4. Heat the flask to
about 60-70oC temperature on a wire gouge. When it becomes
unbearable to touch, the required temperature is reached.
Place
a white paper below the burette and place the titration flask and run the KMnO4
solution from the burette. During titration, operate the stopcock with left
hand and constantly stir the flask with the right hand. Stop addition of the
KMnO4 solution when the end point is reached (pink colour of the solution) and
note the final reading of the burette. The difference between the final and
initial readings gives the volume of the solution used for completion of the
reaction. Repeats the same titration for 3 times so that at least the
concordant readings are observed.
**
Read the upper meniscus of burette reading containing KMnO4 solution.
Observations:
|
S.No
|
Volume of oxalic acid
in ml
|
Burette readings
|
Volume
of
KMnO4
Solution in ml
|
|
|
Initial
|
Final
|
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Molarity
of K2Cr2O7solution is calculated using the
formula:
= 
= |
oxalic acid
|
KMnO4
|
|
Molarity of oxalic
acid solution (M1) = Volume of oxalic acid 7 solution
(V1)=
Moles of oxalic acid solution (n1)
=
|
Molarity
of KMnO4 solution
(M2) =
Volume
of KMnO4 solution ( V2)
=
Moles of KMnO4 Solution (n2)
=
|
Molarity of KMnO4 solution M2 = 
Step:
III -Estimation of Fe2+ by standard solution of KMnO4
solution
Fill potassium permanganate solution to
just above the zero mark of burette. Open the stopcock to remove any air
bubbles in the tip. In a 250 ml conical flask, take 20 ml Mohr’s
salt solution by using a graduated pipette and add 5 ml conc. H2SO4, 5 ml
syrupy phosphoric acid. Read the upper meniscus of burette reading containing
KMnO4 solution.
Place a white paper below the burette and
place the titration flask and run the KMnO4 solution from the burette. During
titration, operate the stopcock with left hand and constantly stir the flask
with the right hand. Stop addition of the KMnO4 solution when the end point is
reached (faint pink colour lasting for 30 seconds) note the final reading of
the burette. The difference between the final and initial readings gives the
volume of the solution used for completion of the reaction. Repeats the same
titration for 3 times so that at least the concordant readings are observed.
Observations
|
S.No
|
Volume of oxalic acid
in ml
|
Burette readings
|
Volume
of
KMnO4
Solution in ml
|
|
|
Initial
|
Final
|
|||
|
|
|
|
|
|
|
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|
|
Molarity
of Mohr’s
salt solution
is calculated using the formula 
= 
= |
KMnO4
|
FeSO4
|
|
Molarity of KMnO4 solution (M2) =
Volume
of KMnO4 solution ( V2)
=
Moles of KMnO4 Solution (n2) =
|
Molarity
FeSO4 solution M3 =
Volume
of FeSO4 solution V3 =
Moles of FeSO4 Solution (n3) =
|
Molarity of Mohr’s salt solution
M3 = 
Amount
of FeSO4 present in 100 ml of the given solution = 
Amount of Fe+2ion present in 100 ml of
the given solution = 
Report:
Ø Molarity
o f the Oxalic acid Solution (M1)=
Ø Molarity
of KMnO4 solution M2 =
Ø Molarity
of Mohr’s
salt solution
M3=
Ø Amount
of FeSO4 present in 100 ml of the given solution=
Ø Amount
of Fe+2ion present in 100 ml of the given solution =
Some important
points and precautions of titration:
Before
preparation of any standard solution all the glassware should be washed
properly so that there no any contamination.
Do not
use excess titrant, because even one more drop of titrant may disturb in
determination of end point.
Reaction
conditions are important factor of redox titration. For example, titration
between KMnO4 and Oxalic acid, the temperature of acid should not less than
60OC and medium should be acidic.
Examine
the stopcock of burette before use. Loose or damage stopcock cannot control.
It is
important to know how to take the reading of burette. The eye level and liquid
surface in the burette should be parallel.
Regent
preparation:
ü 0.02M KMNO4 solution: 3.2 ms in 1 lit. Water
ü 5N H2SO4 : 140ml in lit. Water
ü 0.1M Mohr’s solution : 39.2gms in 1 lit. Water
Estimation
of Fe+2 by KMnO4 as
primary standard Oxalic acid
Aim of
experiment: Estimation of Fe2+ from supplied
solution by standard KMnO4
Principle:
This process was presented by Mabride in 1912. When oxalic acid acidified with
dil.H2SO4 is titrated with potassium permanganate solution at 60-700C
temperature, an oxidation-reduction reaction takes place between these
substances. The chemical reaction is
When solution of Fe2+ ion acidified with dil. H2SO4
is titrated with potassium permanganate solution at room temperature, an
oxidation-reduction reaction takes place between these substances. The chemical
reaction is
Required materials and solutions:
Burette, pipette (20 ml), 250 ml conical flask, 250ml, volumetric flask, oxalic
acid, potassium permanganate, etc.
Part: I- Preparation of standard
solution of oxalic acid
Weigh
accurately 1.125 g of oxalic acid in a chemical balance (or electronic balance)
and transfer it to a 250 ml volumetric flask. Add 100 ml distilled water and
shake vigorously until all the crystal is dissolved. Add again distilled water
up to the mark of flask and it is labeled as standard oxalic acid solution
Observation:
·
Weight of the Empty Bottle (W1)=
·
Weight of the Bottle + compound (W2)=
·
Weight of the Bottle after transfer of
salt (W3)=
·
Weight of the Oxalic acid (W4) = W2-W3=
Molarity o f the Oxalic acid Solution (m1) =
Part-II
Estimation of KMnO4 using standard oxalic acid solution
Take
a clean burette and rinse it with potassium permanganate solution, support it
with a burette clamp. Close the stopcock and with the help of a funnel fill
potassium permanganate solution to just above the zero mark. Open the stopcock
to remove any air bubbles in the tip. In a 250 mL conical flask, take 20 mL
oxalic acid by using a graduated pipette and 5mL conc. H2SO4. Heat the flask to
about 60-70oC temperature on a wire gouge. When it becomes
unbearable to touch, the required temperature is reached.
Place
a white paper below the burette and place the titration flask and run the KMnO4
solution from the burette. During titration, operate the stopcock with left
hand and constantly stir the flask with the right hand. Stop addition of the
KMnO4 solution when the end point is reached (pink colour of the solution) and
note the final reading of the burette. The difference between the final and
initial readings gives the volume of the solution used for completion of the
reaction. Repeats the same titration for 3 times so that at least the
concordant readings are observed.
**
Read the upper meniscus of burette reading containing KMnO4 solution.
Observations:
|
S.No
|
Volume of oxalic acid
in ml
|
Burette readings
|
Volume
of
KMnO4
Solution in ml
|
|
|
Initial
|
Final
|
|||
|
|
|
|
|
|
|
|
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|
|
Molarity
of K2Cr2O7solution is calculated using the
formula: =
= |
oxalic acid
|
KMnO4
|
|
Molarity of oxalic
acid solution (M1) = Volume of oxalic acid 7 solution
(V1)=
Moles of oxalic acid solution (n1)
=
|
Molarity
of KMnO4 solution
(M2) =
Volume
of KMnO4 solution ( V2)
=
Moles of KMnO4 Solution (n2)
=
|
Molarity of KMnO4 solution M2 =
Step:
III -Estimation of Fe2+ by standard solution of KMnO4
solution
Fill potassium permanganate solution to
just above the zero mark of burette. Open the stopcock to remove any air
bubbles in the tip. In a 250 ml conical flask, take 20 ml Mohr’s
salt solution by using a graduated pipette and add 5 ml conc. H2SO4, 5 ml
syrupy phosphoric acid. Read the upper meniscus of burette reading containing
KMnO4 solution.
Place a white paper below the burette and
place the titration flask and run the KMnO4 solution from the burette. During
titration, operate the stopcock with left hand and constantly stir the flask
with the right hand. Stop addition of the KMnO4 solution when the end point is
reached (faint pink colour lasting for 30 seconds) note the final reading of
the burette. The difference between the final and initial readings gives the
volume of the solution used for completion of the reaction. Repeats the same
titration for 3 times so that at least the concordant readings are observed.
Observations
|
S.No
|
Volume of oxalic acid
in ml
|
Burette readings
|
Volume
of
KMnO4
Solution in ml
|
|
|
Initial
|
Final
|
|||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Molarity
of Mohr’s
salt solution
is calculated using the formula =
= |
KMnO4
|
FeSO4
|
|
Molarity of KMnO4 solution (M2) =
Volume
of KMnO4 solution ( V2)
=
Moles of KMnO4 Solution (n2) =
|
Molarity
FeSO4 solution M3 =
Volume
of FeSO4 solution V3 =
Moles of FeSO4 Solution (n3) =
|
Molarity of Mohr’s salt solution
M3 =
Amount
of FeSO4 present in 100 ml of the given solution =
Amount of Fe+2ion present in 100 ml of
the given solution =
Report:
Ø Molarity
o f the Oxalic acid Solution (M1)=
Ø Molarity
of KMnO4 solution M2 =
Ø Molarity
of Mohr’s
salt solution
M3=
Ø Amount
of FeSO4 present in 100 ml of the given solution=
Ø Amount
of Fe+2ion present in 100 ml of the given solution =
Some important
points and precautions of titration:
Before
preparation of any standard solution all the glassware should be washed
properly so that there no any contamination.
Do not
use excess titrant, because even one more drop of titrant may disturb in
determination of end point.
Reaction
conditions are important factor of redox titration. For example, titration
between KMnO4 and Oxalic acid, the temperature of acid should not less than
60OC and medium should be acidic.
Examine
the stopcock of burette before use. Loose or damage stopcock cannot control.
It is
important to know how to take the reading of burette. The eye level and liquid
surface in the burette should be parallel.
Regent
preparation:
ü 0.02M KMNO4 solution: 3.2 ms in 1 lit. Water
ü 5N H2SO4 : 140ml in lit. Water
ü 0.1M Mohr’s solution : 39.2gms in 1 lit. Water
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