Short Answer TypeCopper crystallises with face centred cubic unit cell. If the radius of a copper atom is 127.8 pm, calculate the density of the copper metal.
(Atomic mass of Cu = 63.55 u and Avogadro’s number NA = 6.02 x 1023 mol-1)
Iron has a body centred cubic unit cell with the cell dimension of 286.65 pm. The density of iron is 7.87 g cm-3. Use this information to calculate Avogadro’s number. (Atomic mass of Fe = 56.0 u)
The reaction N2(g) + O2(g) 2NO(g), contributes to air pollution whenever a fuel is burnt in air at a high temperature. At 1500 K, equilibrium constant K for it is 1.0 x 10-5. Suppose in a case [N2] = 0.80 mol L-1and [O2] = 0.20 mol L-1 before any reaction occurs. Calculate the equilibrium concentrations of the reactants and the product after the mixture has been heated to 1500 K.
The electrical resistance of a column of 0.05 M NaOH solution of diameter 1cm and length 50
cm is 5.55 x 103 ohm. Calculate its resistivity, conductivity and molar conductivity.
Write three distinct features of chemisorptions which are not found in physisorptions.
Explain each of the following observations:
(i) With the same d-orbital configuration (d4), Cr2+ is a reducing agent while Mn3+ is an oxidising agent.
(ii) Actinoids exhibit a much larger number of oxidation states than the lanthanoids.
(iii) There is hardly any increase in atomic size with increasing atomic number in a series of transition metals.
(i) Outer electronic configuration f Mn is 3d5 4s2.
Outer electronic configuration of Mn3+ is 3d4 4s0.
Now Mn3+ is a strong oxidizing agent. A good oxidizing agent reduces itself. I.e. gains electrons from other. Its tends to gain one more electron to acquire stable electronic configuration. If it gains one electron, its configuration will be 3d5, which is stable .this is the reason, it acts as a good reducing agent.
Cr2+ is strongly reducing agent in nature. It has d4 configuration. While acting as a reducing agent, it gets oxidized to Cr3+ such as d3. This d3 configuration can be written as t32g configuration, which is more stable configuration.
(ii) In actinoids, the 5f, 6d, 7s shells are present. These three shells are of comparable energies; therefore electrons can remove from these shells. This gives rise f variable oxidation states in actinoids.
Following are the similarities between actinoids and lanthanoids:
(a) The size of atom: It decreases across the series in both actinoids (due to actinoid contraction) and lanthanoids (due to lanthanoids contraction).
(b) Oxidation states: Lanthanoids and actinoids generally show +3 oxidation states. However, some element in the actinoids series is capable of exhibiting oxidation states higher than +3
(iii) The atomic sizes of the elements of the first transition series are smaller than those of the heavier elements (elements of 2nd and 3rd transition series).
However, the atomic sizes of the elements in the third transition series are virtually the same as those of the corresponding members in the second transition series. This is due to lanthanoid contraction.
Name of the following coordination entities and describe their structure:
(i) [Fe (CN)6]4-
(ii) [Cr (NH3)4Cl2]+
(iii) [Ni (CN) 4]2-
(Atomic numbers Fe = 26. Cr = 24, Ni = 28Write a reaction which shows that all the carbon atoms in glucose are linked in a straight chain.
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