Advertisements
Advertisements
प्रश्न
Compare the stability of +2 oxidation state for the elements of the first transition series.
Advertisements
उत्तर १
| Sc | +3 | ||||||
| Ti | +2 | +3 | +4 | ||||
| V | +2 | +3 | +4 | +5 | |||
| Cr | +2 | +3 | +4 | +5 | +6 | ||
| Mn | +2 | +3 | +4 | +5 | +6 | +7 | |
| Fe | +2 | +3 | +4 | +6 | |||
| Co | +2 | +3 | +4 | ||||
| Ni | +2 | +3 | +4 | ||||
| Cu | +1 | +2 | |||||
| Zn | +2 |
उत्तर २
Firstly, in the first half of the transition series, the sum of the first- and second-ionisation enthalpies increases with atomic number. Hence, the standard reducing potential (E°) is low and negative. Hence, the tendency to form M2+ ions decreases. Hence, the +2 oxidation state is more stable in the first half. The greater stability of the +2 oxidation state is due to half-filled d-subshells (d5) in Mn2+, fully filled d-subshells (d10) in Zn2+, and high negative hydration enthalpy in nickel.
संबंधित प्रश्न
Why do the transition elements have higher enthalpies of atomisation?
Account for the following:
Cu+ ion is unstable in aqueous solution.
Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only?
To what extent do the electronic configurations decide the stability of oxidation states in the first series of the transition elements? Illustrate your answer with examples.
How would you account for the following:
Cobalt (II) is stable in aqueous solutions, but in the presence of complexing reagents, it is easily oxidised.
Which metal in the first series of transition metals exhibits +1 oxidation state most frequently and why?
Read the passage given below and answer the following question:
The transition metals when exposed to oxygen at low and intermediate temperatures form thin, protective oxide films of up to some thousands of Angstroms in thickness. Transition metal oxides lie between the extremes of ionic and covalent binary compounds formed by elements from the left or right side of the periodic table. They range from metallic to semiconducting and deviate by both large and small degrees from stoichiometry. Since electron bonding levels are involved, the cations exist in various valence states and hence give rise to a large number of oxides. The crystal structures are often classified by considering a cubic or hexagonal close-packed lattice of one set of ions with the other set of ions filling the octahedral or tetrahedral interstices. The actual oxide structures, however, generally show departures from such regular arrays due in part to distortions caused by packing of ions of different size and to ligand field effects. These distortions depend not only on the number of d-electrons but also on the valence and the position of the transition metal in a period or group.
In the following questions, a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices on the basis of the above passage.
Assertion: Transition metals form protective oxide films.
Reason: Oxides of transition metals are always stoichiometric.
Generally transition elements form coloured salts due to the presence of unpaired electrons. Which of the following compounds will be coloured in solid-state?
Which of the following ions show higher spin only magnetic moment value?
(i) \[\ce{Ti^3+}\]
(ii) \[\ce{Mn2+}\]
(iii) \[\ce{Fe2+}\]
(iv) \[\ce{Co3+}\]
Match the catalysts given in Column I with the processes given in Column II.
| Column I (Catalyst) | Column II (Process) |
| (i) \[\ce{Ni}\] in the presence of hydrogen | (a) Zieglar Natta catalyst |
| (ii) \[\ce{Cu2C12}\] | (b) Contact process |
| (iii) \[\ce{V2O5}\] | (c) Vegetable oil to ghee |
| (iv) Finely divided iron | (d) Sandmeyer reaction |
| (v) \[\ce{TiCl4 + Al (CH3)3}\] | (e) Haber's Process |
| (f) Decomposition of KCIO3 |
Which of the following is non-metallic?
The orientation of an atomic orbital is governed by
Which of the following statements is not correct?
Which one of the following characters tie of the transition metal is associated with higher catalytic activity?
On adding NaOH, solution to the aqueous solution of K2CrO7 the colour of the solution changes from
Give reason for the following statement:
[Ti(H2O)]3+ is coloured while [Sc(H2O)6]3+ is colourless.
The value of Δ0 for \[\ce{RhCl^{3-}6}\] is 243 KJ/mol which wavelength of light will promote an electron from. The colour of the complex is ______.
The oxidation state of Fe in [Fe(CO)5] is ______.
Complete the following reaction and justify that it is a disproportionation reaction:
\[\ce{3MnO^{2-}4 + 4H^+ -> \underline{}\underline{}\underline{}\underline{} + \underline{}\underline{}\underline{}\underline{} + 2H2O}\]
Which of the following ions has the electronic configuration 3d6?
(Atomic number: Mn = 25, Co = 27, Ni = 28)
