The d and f Block Elements
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17. Although Cr3+ and Co2+ ions have same number of unpaired electrons but the magnetic moment of Cr3+ is 3.87 BM and that of Co2+ is 4.87 BM. Why?
17. Although Cr3+ and Co2+ ions have same number of unpaired electrons but the magnetic moment of Cr3+ is 3.87 BM and that of Co2+ is 4.87 BM. Why?
17. Magnetic moment of an electron/dipole moment is caused by its intrinsic properties of spin and electric charge. It depends upon the number of unpaired electrons in its valence shell. The more the number of unpaired electrons, the greater will be the value of magnetic moment.
Cr3+
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16. Although fluorine is more electronegative than oxygen, the ability of oxygen to stabilize higher oxidation states exceeds that of fluorine. Why?
16. Although fluorine is more electronegative than oxygen, the ability of oxygen to stabilize higher oxidation states exceeds that of fluorine. Why?
16. Fluorine - 1s22s22p5
Oxygen - 1s2 2s2 2p6 3s2 3p6
As we can infer from the electronic configuration, fluorine only has one unpaired electron in its 2p-orbital which can be involved in formation of only one bond and fluorine lacks d-orbital.
While oxy
Upvote 15. When a brown compound of manganese
(A) Is treated with HCl, it gives a gas
(B) The gas taken in excess, reacts with NH3 to give an explosive compound
(C) Identify compounds A, B and C.
15. When a brown compound of manganese
(A) Is treated with HCl, it gives a gas
(B) The gas taken in excess, reacts with NH3 to give an explosive compound
(C) Identify compounds A, B and C.
15. The reactions are explained as:
MnO2 + 4HCl → MnCl2 + Cl2 + 2H2O
(A) (B)
3Cl2 + 2NH3 →
Upvote 14. Out of Cu2Cl2 and CuCl2, which is more stable and why?
14. Out of Cu2Cl2 and CuCl2, which is more stable and why?
14. Higher enthalpy of hydration provides extra stability to Cu2+ oxidation state than +1 oxidation state.
Enthalpy of hydration is described as the amount of energy released on dilution of one mole of gaseous ions.
Upvote 13. When Cu2+ ion is treated with KI, a white precipitate is formed. Explain the reaction with the help of a chemical equation.
13. When Cu2+ ion is treated with KI, a white precipitate is formed. Explain the reaction with the help of a chemical equation.
13. 2Cu2+ + 4I- → Cu2I2 + I2
When Cu2+ reacts with potassium iodide white precipitate of Cu2I2 is formed.
Upvote 12. Transition elements have the ability to involve their d-electrons along with their s-electrons in the process of bond formation. This results in formation of strong metal-metal bonds which makes their melting point high.
Upvote 11. Why is the first ionization enthalpy of Cr lower than that of Zn?
11. Why is the first ionization enthalpy of Cr lower than that of Zn?
11. Cr (24)= [Ar]3d54s2
Zn (30) = [Ar] 3d104s2
The stability of orbitals according to the electrons filled is in order:
Fully filled > half-filled > partially filled
As 3d10 is completely filled orbital of Zn is more stable than the 3d5 half-filled orbi
Upvote 10. Why E? value for Mn, Ni and Zn are more negative than expected?
10. Why E? value for Mn, Ni and Zn are more negative than expected?
10. Mn has half-filled 3d5 electrons and Zn has fully-filled 3d10 electrons which give them extra stability and they both resist to lose electrons and get reduced.
The E? value also depends on the hydration enthalpy. More negative is the enthalpy of hydration, high is the E? value. This is the
Upvote 9. Copper lies below hydrogen in electrochemical series which means it has positive standard reduction potential i.e. + 0.34 V. and hence cannot liberate hydrogen from acids.
Upvote 8. A violet compound of manganese (A) decomposes on heating to liberate oxygen and compounds (B) and (C) of manganese are formed. Compound (C) reacts with KOH in the presence of potassium nitrate to give compound (B). On heating compound (C) with conc. H2SO4 and NaCl, chlorine gas is liberated and a compound (D) of manganese along with other products is formed. Identify compounds A to D and also explain the reactions involved.
8. A violet compound of manganese (A) decomposes on heating to liberate oxygen and compounds (B) and (C) of manganese are formed. Compound (C) reacts with KOH in the presence of potassium nitrate to give compound (B). On heating compound (C) with conc. H2SO4 and NaCl, chlorine gas is liberated and a compound (D) of manganese along with other products is formed. Identify compounds A to D and also explain the reactions involved.
8. KMnO4 
K2MnO4 + MnO2 + O2
(A) (B) (C)
MnO2 + KOH → 2K2MnO4 + 2H2O
MnO2 + 4NaCl +
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