prepare m/ 10 solution of more salt and using the solution determine the molarity and strength
Answers
Answer:
The titration of potassium permanganate (KMnO4) against Mohr salt is an example of redox titration. In close proximity to the endpoint, the action of the indicator is analogous to the other types of visual colour titrations in oxidation-reduction (redox) titrations.
Aim:
To determine the strength of a given potassium permanganate solution against standard ferrous ammonium sulfate (Mohr’s salt) solution.
Theory:
Potassium permanganate is a strong oxidant in the presence of sulfuric acid. Mohr salt is a double salt forming a single crystalline structure having the formula (NH4</sub2SO4. FeSO4. 6H2O. The chemical name for Mohr’s salt is ferrous ammonium sulfate.
In this titration Mohr salt acts as a reducing agent and potassium permanganate acts as an oxidising agent. So, the reaction between Mohr’s salt and potassium permanganate is a redox reaction. In this redox reaction, ferrous ion from Mohr’s salt gets oxidised and pink coloured of manganese present in potassium permanganate, which is in the +7 oxidation state gets reduced to colourless Mn2+ state.
The chemical reaction and the molecular chemical equation is given below.
Reduction half reaction –
2KMnO4 + 3H2SO4 → K2SO4 + 2MnSO4 + 3H2O + 5[O]
Oxidation half reaction –
2FeSO4(NH4)2SO4.6H2O + H2SO4 + 5[O] → Fe2(SO4)3 + 2(NH4)2SO4 + 13H2O x 5
Overall reaction –
2KMnO4 + 10FeSO4(NH4)2SO4.6H2O+8H2O → K2SO4+ 2MnSO4+ 5Fe2(SO4)3+ 10(NH4)2SO4+ 68H2O
The ionic equation involved in the process is given below.
Oxidation half reaction – [Fe2+ → Fe3+ – e–] x 5
Reduction half reaction – MnO4– + 8H+ + 5e– → Mn2+ + 4H2O
Overall ionic equation – MnO4– + 8H+ + 5Fe2+ → Mn2+ + 5Fe3+ + 4H2O
This titration is based upon oxidation-reduction titrations. When ferrous ammonium sulfate solution is titrated against potassium permanganate in the presence of acidic medium by sulfuric acid. Acidic medium is necessary in order to prevent precipitation of manganese oxide. Here KMnO4 acts as a self indicator and this titration is called permanganate titration.
Materials Required:
Mohr’s salt (ferrous ammonium sulfate)
Potassium permanganate solution
Dilute sulfuric acid
Chemical balance
Burette
Burette stand
Pipette
Conical flask
Funnel
Measuring flask
Weighing bottle
White tile
Burnet
Wire gauze
Answer:
AIM OF THE EXPERIMENT - To Prepare M/10 solution of the Mohr's salt and using the solution determine its molarity and strength.
APPARATUS REQUIRED -
1. Burette
2. Pipette
3. beakers
4. flask
5. funnel
6. weighing balance
7. weight box
CHEMICALS USED -
1. Mohr's Salt crystals
2. KMnO4 solution.
3. Concentrated H₂SO₄ and dilute H₂SO₄
INDICATORS USED -
KMnO₄ is used as a self indicator.
THEORY -
KMNo4 will act as an oxidizing agent with the presence of H₂SO₄ whereas, Mohr's salt will be acting as a reducing agent.
MOLECULAR EQUATION -
2KMnO₄ + 3H₂SO₄ --> K₂SO₄ + 2MnSO₄ + 3H₂O + 5(O)
2FeSO₄ + (O) + H₂SO₄ --> Fe₂(SO₄)₃ + H₂O }X5
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2KMnO₄ + 8H₂SO₄ + 10FeSO₄ --> K₂SO₄ + 2MnSO₄ + 5Fe₂(SO₄)₃ + 8H2O
IONIC EQUATION -
MnO⁴⁻ + 8H⁺ + 5e⁻ --> Mn²⁺ + 4H₂O [REDUCTIO REACTION]
Fe²⁺ --> Fe³⁺ + e⁻ }x5 {OXIDATION REACTION]
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MnO⁴⁻ + 8H⁺ + 5Fe²⁺ --> Mn²⁺ + 4H₂O + 5Fe³⁺ [OVERALL REACTION]
PREPARATION OF M/10 MOHR'S SALT -
By default the molecular mass of Mohr's salt is 392g
Therefore, amount of the Mohr's salt in M/10 used is 392/10 = 39.2g
For 250ml, it will be = 39.2 x 250/1000 = 9.8g
1. Now, take 9.8g of the Mohr's salt and then dissolve it into the given water
2. Then, add 5ml o concentrated H₂SO₄ to the solution.
3. Then take 250ml volumetric flask and then transfer the total solution and then mark it up to 250ml.
4. We will see a change from the colorless solution to a pink one.
NB -
volume of kMnO₄ solution in ml
Prepare a table to record the volume of the pipette solution(V2) in ml.
Volume of Burette solution (both initial and final) in ml.
and the concordant reading.
TO CALCULATE THE MOLARITY AND STRENGTH -
5 x M1V1 = 1 x M2V2
where,
M1 = molarity of KMnO4
M2 = molarity of Mohr's salt (M/10)
V1 = volume of KMnO4 (18.8ml)
V2 = volume of Mohr's salt (20ml)
and strength of the solution = M1 x 158 gm/l
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