In presence of KClO3 & KNO3 the above reaction is more faster because these two on decomposition provides O2 easily.
Manganate is also obtained when KMnO4 is boiled with KOH.
4 KMnO4 + 4KOH 4K2MnO4 + 2H2O + O2
3K2MnO4 + 2H2SO4 → 2KMnO4 + MnO2 + 2K2SO4 + 2H2O
or 3K2MnO4 + 2H2O + 4CO2 → 2KMnO4 + MnO2 + 4KHCO3
But in the above method of Mn is lost as MnO2 but when oxidised either by Cl2or by O3
2K2MnO4 + Cl2 → 2KMnO4 + 2KCl [Unwanted MnO2 does not form]
OR
2K2MnO4 + O3 + H2O → 2KMnO4 + 2KOH + O2
3K2MnO4 + 2H2O 2KMnO4 + MnO2¯ + 4KOH
purple dark brown
Prob : =
(1) It is not a primary standard since it is difficult to get it in a high degree of purity and free from trances of MnO2.
(2) It is slowly reduced to MnO2 especially in presence of light or acid
4 MnO4- +4 H+ → 4 MnO2 + 2H2O + 3O2
Hence it should be kept in dark bottles and standardise just before use.
(viii) 2 KMnO4 + 16 HCl → 2KCl + 5Cl2 + 8H2O + 2MnCl2
2 MnO4- + 2OH- → 2MnO42- + H2O + O.
Then 2MnO42- + 2H2O → 2MnO2 + 4OH- + 2O
(i) 2KMnO4 + 3 MnSO4 + 2H2O 5 MnO2 + K2SO4 + 2H2SO4
or MnO4- + Mn+2 + 2H2O → 5MnO2 + 4H+
In absence of Zn+2 ions, some of the Mn+2 ion may escape, oxidation through the formation of insoluble MnII[MnIVO3] manganous permanganite.
(ii) 8 KMnO4 + 3Na2S2O3 + H2O → 8 MnO2 + 3 Na2SO4 + 3 S + 2 KOH
(i) PbO2
(ii) Pb3O4 + HNO3
(iii) Pb2O3
(iv) NaBiO3/H +
(v) (NH4)2S2O8 /H +
(vi) KIO4/H+
Heating effect : 2KMnO4 K2MnO4 + MnO2 + O2
2K2MNO4 2K2MnO3 + O2
In the same way in presence of O2, Ag complexes with NaCN/KCN.
4 Ag + 8 KCN + 2H2O + O2 ⇒ 4K[Ag(CN)2] + 4KOH
AgCl, AgBr, AgI (but not Ag2S) are soluble in Na2S2O3 forming [Ag(S2O3)2]-3 complexes
2 AgNO3 2AgNO2 + O2
2 AgNO3 2Ag 2NO+ O2
(VIII)
Ag2O +H2O2 → 2Ag+ H2O +O2
K2S2O8 +2AgNO3 +2H2O → 2AgO +2KHSO4 +2HNO3
ZnO : It is called as phillospher's wool due to its wooly flock type appearance
4ZnSO4 +4Na2CO3 +3H2O → ZnCO3.3Zn(OH)2¯ + 4Na2SO4 +3CO2
Anhydrous ZnCl2 cannot be made by heating ZnCl2.2H2O because
ZnCl2.2H2O Zn(OH)Cl +HCl +H2O
Zn(OH)Cl ZnO +HCl
To get anh. ZnCl2 : Zn +Cl2 → ZnCl2
Zn +2HCl(dry) → ZnCl2 +H2
or Zn +HgCl2 → ZnCl2 +Hg
(i) It is deliquescent white solid (when anhydrous)
(ii) ZnCl2 + H2S → ZnS
+NaOH → Zn(OH)2 Na2[Zn(OH)4]
+NH4OH → Zn(OH)2 [Zn(NH3)4]2
Zn +dil. H2SO4 → ZnSO4 + H2
ZnO+ dil H2SO4 → ZnSO4 + H2O
ZnCO3 + dil H2SO4 → ZnSO4 + H2O+ CO2
ZnS +2O2 → ZnSO4
ZnS+ O2 → ZnO+ SO2
ZnS +4O3 → ZnSO4 + 4O2
ZnSO4 . 7H2O ZnSO4 . 6H2O
(i) CuCO3. Cu(OH)2 2CuO +H2O +CO2 (commercial process)
Malachite Green
(native Cu-carbonate)
(ii) 2Cu O2 → 2CuO & Cu2O +O2 → 2CuO
(iii) Cu(OH)2 CuO +H2O
(iv) 2Cu(NO3)2 2CuO +4NO2 +O2
CuO+ 2HCl (conc.) → CuCl2 +H2O
Cu(OH)2.CuCO3 +4HCl → 2CuCl2 +3H2O +CO2
(i) It is crystallised as CuCl2. 2H2O of Emerald green colour
(ii) Dil. solution in water is blue in colour due to formation of [Cu(H2O)4]2 complex.
(iii) Conc. HCl or KCl added to dil. solution of CuCl2 the colour changes into yellow, owing to the formation of [CuCl4]2- .
(iv) The conc. aq. solution is green in colour having the two complex ions in equilibrium 2[Cu(H2O)4]Cl2 [Cu(H2O)4]2 + [CuCl4]2- + 4H2O
(v) CuCl2 → CuCl by no. of reagents
(a) CuCl2 +Cu-turnings 2CuCl
(b) 2CuCl2 + H2SO3 + H2O → 2CuCl+ 2HCl +2H2SO4
(c) 2CuCl2 +Zn/HCl → 2CuCl +ZnCl2
(d) CuCl2 + SnCl2 → CuCl +SnCl4
CuI2 does not exist.
CuCl2.2H2O CuCl2 + 2H2O
(i) Preparation : -
CuO + H2SO4(dil) → CuSO4 + H2O
Cu(OH)2 + H2SO4(dil) → CuSO4 + 2H2O
Cu(OH)2.CuCO3 + H2SO4(dil) → CuSO4+ 3H2O+ CO2
Cu H2SO4 + O2 → CuSO4 + H2O [Commercial scale]
(Scrap)
Cu dil. H2SO4 → no reaction {Cu is below H in electrochemical series}
(i) It is crystallised as CuSO4.5H2O
(ii)
(iii) Revision with all others reagent
(i) It undergoes aerial oxidation forming basic ferric sulphate
4FeSO4 + H2O + O2 → 4Fe(OH)SO4
(ii) FeSO4.7H2O FeSO4 Fe2O3 +SO2 +SO3
anh.white
(iii) Aq. solution is acidic due to hydrolysis
FeSO4 + 2H2O Fe(OH)2 + H2SO4 (weak base
(iv) It is a reducing agent
(a) Fe2+ + MnO4- + H+ → Fe3++Mn2+ + H2O
(b) Fe2 +Cr2O72- +H+ → Fe3+ +Cr3 + +H2O
(c) Au3+ + Fe2+ → Au+ Fe3+
(d) Fe2+ +HgCl2 → Hg2Cl2¯ +Fe3+ (white ppt.)
(v) It forms double salt.
Example (NH4)2SO4. FeSO4.6H2O
FeC2O4 FeO +CO +CO2
It is stable at high temperature and on cooling slowly disproportionates into
Fe3O4 and iron.
4FeO → Fe3O4 +Fe
Fe+ 2HCl FeCl2 +H2
or 2FeCl3 + H2 2 FeCl2 +2HCl
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