to prepare 200ml of M/100 mohr's salt solution and with this M/100 mohr's salt solution find out the molarity and strength of the given unknown kmno4 solution
Answers
Answer:
Aim:
Prepare M/20 solution of ferrous ammonium sulphate (Mohr's Salt). Using this solution, find out the molarity and strength of the given KMnO4solution.
Theory:
Molecular mass of Mohr's Salt FeSO4.(NH4)2SO4.6H2O = 392
Therefore to prepare 1000 ml of 1M Mohr's Salt solution, we need 392g of it.
Therefore to prepare 250 ml of M/20 Mohr's Salt solution, we need
392/1000 * 250 * 1/20 = 4.9g
Apparatus required:
Watch glass, beaker, measuring cylinder, pipette, burette, wash bottle, conical flask.
Chemicals required:
Mohr's salt, concentrated H2SO4, M/100 KMnO4solution.
Chemical equations:
Molecular equations-
2KMnO4 + 3H2SO4 -> K2SO4 + 2MnSO4 + 3H2SO4+ 5[O].
[2FeSO4(NH4)2SO4.6H2O + H2SO4 + [O] -> Fe(SO4)3 + 2(NH4)2SO4 + 13H2O]*5
2KMnO4 + 8H2SO4 + 10 FeSO4.6H2O -> K2SO4 + 2MnSO4 + 5Fe2(SO4)3 + 10(NH4)2 + 68H2O
Ionic equations-
MnO4- + 8H+ + 5e- -> Mn2+ + 4H2O
[Fe2+ -> Fe3+ ]*5
MnO4- + 8H+ + 5Fe2+ -> 5Fe3+ + Mn2+ + 4H2O
Indicator:
KMnO4 is a self indicator.
End point:
Colorless to permanent pink color (KMnO4 in the burette).
Observations:
Weight of watch glass = 18g Weight of watch glass + Mohr's Salt = 22.9g Weight of Mohr's Salt = 4.9g
Volume of Mohr's salt solution prepared = 250 ml Molarity of Mohr's salt solution = M/20 Volume of Mohr's salt solution atken for each titration = 10 ml
Calculations:
a) Molarity of KMnO4 solution- From the overall balanced equation, it is clear that 2 moles of KMnO4 react with 10 moles of Mohr's Salt
(MKMnO4 * VKMnO4) / (MMohr's Salt * VMohr's Salt) = 2/10 where M stands for molarity, and V for volume.
Therefore MKMnO4 = 0.01M (Approximately).
b) Strength of the KMnO4 solution. Strength (in g/L) = Molarity * Molar Mass = 0.01 * 158 = 1.58 g/L
Result:
The molarity of the given KMnO4 solution is 0.01M. The strength of the given KMnO4 solution is 1.58g/L.
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Explanation: