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Question : 35
Total: 37
SECTION -D
(a) Give reasons:
(i) Transition metals and their compounds show catalytic activities.
(ii) Separation of a mixture of Lanthanoid elements is difficult.
(iii)
(b) Write the preparation of the following :
(i)
(ii)
OR
(a) Account for the following:
(i)
(ii)
(b) Write two similarities between chemistry of lanthanoids and actinoids.
(c) Complete the following ionic equation:
Solution:
(a) (i) The catalytic activities of transition metals and their compounds is due to the ability of adopt variable oxidation states and to form complexes. It can also provide a large surface area for the reactants to be adsorbed. (Any one)
(ii) Separation of lanthanoid elements is difficult because all lanthanoid elements have almost similar physical as well as chemical properties. Due to the lanthanoid contraction the change in the atomic or ionic radii is very small.
(iii)Zn , Cd Mg d
(b) (i)2 Na 2 CrO 4 + H 2 SO 4 → Na 2 Cr 2 O 7 + Na 2 SO 4 + H 2 O
(ii)2 MnO 2 + 4 KOH + O 2 → 2 K 2 MnO 4 + 2 H 2 O
OR
(a) (i)Ti 3 + d ( 3 d 1 ) Sc 3 + ( 3 d ∘ ) d
(ii)Cr 2 + Cr 3 +
(b) Similarities between chemistry of lanthanoids and actinoids:
(i) Both show +3 oxidation state.
(ii) Both are strong reducing agents.
(c)3 MnO 4 2 − + 4 H + → 2 MnO 4 − + MnO 2 + 2 H 2 O
(ii) Separation of lanthanoid elements is difficult because all lanthanoid elements have almost similar physical as well as chemical properties. Due to the lanthanoid contraction the change in the atomic or ionic radii is very small.
(iii)
(b) (i)
(ii)
OR
(a) (i)
(ii)
(b) Similarities between chemistry of lanthanoids and actinoids:
(i) Both show +3 oxidation state.
(ii) Both are strong reducing agents.
(c)
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