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CrO42- (yellow) changes to Cr2O72- (orange) in pH =x and vice versa in pH=y. Hence, x and y are:
(a) 2CrO42-+ 2H+Cr2O72-+H2O
Cr2O72-+2OH-2CrO42-+H2O
When steam is passed over red hot iron , the substances formed are:
When steam is passed over red hot iron, the reaction that takes place is: 3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g). Iron is oxidized to Fe3O4 (iron(II,III) oxide or magnetite), and hydrogen gas is evolved. This reaction is used in the industrial production of hydrogen gas.
Which of the following solid salt on heating with K2Cr2O7 and Conc. H2SO4 orange,red vapours are evolved which turn aquous NaOH solution yellow?
(b) NaCl(s) + K2Cr2O7 + H2SO4 (few drops)CrO2Cl2+H2O
CrO2Cl2 + OH-(aq.)CrO4(aq)2-+Cl-+2H2O
Fe is made passive by :
(c)
Formation of a thin layer of oxide upon the surface of metal, which protects the inner surface of metal to come in direct contact of air or other chemicals for reaction.
The iron salt used in blue prints is:
Which has highest melting point?
The colour of KMnO4 is due to
In KMnO4, Mn has no d-electron and colour is due to charge transfer spectra
Which of the following element does not show the variable oxidation state?
Pseudo transition element have 10 electro in d subshell , so cannot lose electron from d subshell.
With F highest stable oxidation state of Mn is
MnF4
Mn has 2 s electrons and five d. The s electrons can be unpaired to the 4p orbital..But almost three d orbitals can be used to form sigma bonds
Why?..
dz2 and dx2-y2 are the only two orbitals axially oriented and suited for head on sigma overlap…the other orbitals ar oriented in between axes . So they can only form pi bonds.
However…atmoat 1 non axial d orbital can be used so that just enough limiting stability is present in the molecule so formed as the involvement of Pi character in a sigma bond weakens it.
Cr2O72-+XCr3++H2O + oxidized product of X, X in the above reaction cannot be
SO42- can't be oxidised because S has highest oxidation state i.e. +6
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