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प्रश्न
What is meant by ‘disproportionation’?
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उत्तर
The oxidation and reduction of a substance at the same time as a result of a chemical reaction is called disproportionation.
संबंधित प्रश्न
Explain why is Fe3+ more stable than Fe2+?
Compare the stability of +2 oxidation state for the elements of the first transition series.
Write the formula of an oxo-anion of Chromium (Cr) in which it shows the oxidation state equal to its group number
Following are the transition metal ions of 3d series:
Ti4+, V2+, Mn3+, Cr3+
(Atomic numbers: Ti = 22, V = 23, Mn = 25, Cr = 24)
Answer the following:
1) Which ion is most stable in an aqueous solution and why?
2) Which ion is a strong oxidising agent and why?
3) Which ion is colourless and why?
Give reasons:
E° value for the Mn3+/Mn2+ couple is much more positive than that for Fe3+/Fe2+.
Why do transition elements show variable oxidation states ? In 3d series (Sc to Zn), which elements shows the maximum number of oxidation state and why ?
Two metallic elements A and B have the following standard oxidation potentials: A = 0·40v B = - 0·80v. What would you expect if element A was added to an aqueous salt solution of element B? Give a reason for your answer.
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: Cations of transition elements occur in various valence states.
Reason: Large number of oxides of transition elements are possible.
Electronic configuration of a transition element X in +3 oxidation state is [Ar]3d5. What is its atomic number?
The magnetic nature of elements depends on the presence of unpaired electrons. Identify the configuration of transition element, which shows highest magnetic moment.
Interstitial compounds are formed when small atoms are trapped inside the crystal lattice of metals. Which of the following is not the characteristic property of interstitial compounds?
While filling up of electrons in the atomic orbitals, the 4s orbital is filled before the 3d orbital but reverse happens during the ionisation of the atom. Explain why?
Assertion (A): Cu cannot liberate hydrogen from acids.
Reason (R): Because it has positive electrode potential.
On the basis of the figure given below, answer the following questions:
- Why Manganese has lower melting point than Chromium?
- Why do transition metals of 3d series have lower melting points as compared to 4d series?
- In the third transition series, identify and name the metal with the highest melting point.
The element with atomic number 53 belongs to
Which does not belong to first transition series?
Which of the following maxm magnetic moment?
The electrode potential of M2+/M of 3d-series elements shows the positive value for ______.
Give two similarities in the properties of Sc and Zn.
Give a reason for the following:
Zinc, cadmium and mercury are considered as d-block elements but not regarded as transition elements.
