Download App

The d & f Block Elements — Chemistry STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 ScienceChemistryThe d & f Block Elements5 Marks
Question

Answer the following questions:

  1. The figure given alongside illustrates the first ionization enthalpies of first, second and third series of transition elements. Answer the question that follows:
  2. Which series amongst the first, second and third series of transition elements have the highest first ionization enthalpy and why?
  3. Separation of lanthanoid elements is difficult. Explain.
  4. Sm2+, Eu2+ and Yb2+ ions in solutions are good reducing agents but an aqueous solution of Ce4+ is a good oxidising agent. Why?

✓

Answer

  1. Third series has the highest first ionization energy due to poorest shielding effect of the fully filled 4fsubshell.
  2. This is due to lanthanoid contraction.
  3. Sm2+, Eu2+ and Yb2+ ions are good reducing agents as they tend to acquire common oxidation state of +3 shown by lanthanoids by the loss of one electron while Ce4+ gains one electron to attain +3. Hence, Ce4+ is an oxidising agent.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "Long Answer Type Questions [5M]" from The d & f Block Elements→The d & f Block Elements — all question types→Chemistry STD 12 Science question papers→Bihar Board STD 12 Science question papers→Bihar Board question paper generator→

Similar questions

  1. Give reasons for the following:
  1. Mn3+ is a good oxidizing agent.
  2. Eo m2+/M values are not regular for first row transition metals. (3d series)
  3. Although ‘F’ is more electronegative then ‘O’, the highest Mn fluoride is Mnf4, whereas the highest oxide is Mn2O7.
  1. Complete the following equations:

$\text{2CrO}_{4}^{2}+\text{2H}^{+}\rightarrow$

$\text{KMnO}_{4}\xrightarrow{heat}$

→
Arrange the following compounds in a decreasing order of basic strength in their aqueous solutions.
NH3, CH3NH2, (CH3)2NH, (CH3)3N
→
Explain the following reactions of phenol :
(i) Nitration
(ii) Gatterman aldehyde synthesis
(iii) Fries rearrangement
(iv) Reaction with mercuric acetate.
→
Account for the following :
(i) $p K _b$ of aniline is more than that of methylamine.
(ii) Ethylamine is soluble in water whereas aniline is not.
(iii) Methylamine in water reacts with ferric chloride to precipitate hydrated ferric oxide.
(iv) Aniline does not undergo Friedel-Crafts reaction.
(v) Diazonium salts of aromatic amines are more stable than those of aliphatic amines.
→
Answer the following questions:
Give chemical reactions for the following observations:
  1. Potassium permanganate is a good oxidising agent in basic medium.
  2. Inter convertibility of chromate ion and dichromate ion in aqueous solution depends upon pH of the solution.
  3. Potassium permanganate is thermally unstable at 513K.
→
Which of the following compounds would undergo aldol condensation, which the Cannizzaro reaction and which neither? Write the structures of the expected products of aldol condensation and Cannizzaro reaction.
  1. Methanal
  2. 2-Methylpentanal
  3. Benzaldehyde
  4. Benzophenone
  5. Cyclohexanone
  6. 1-Phenylpropanone
  7. Phenylacetaldehyde
  8. Butan-1-ol
  9. 2,2-Dimethylbutanal.
→
Describe the methods of studying various first order reactions with examples.
→
The time required for 10% completion of a first order reaction at 298 K is equal to that required for its 25% completion at 308 K. If the value of A is 4 × 1010 s-1 Calculate k at 318 K and Ea.
→
Attempt any five of the following:
(a) What is the structural feature characterising reducing sugars?
(b) What type of linkage is present in polysaccharides?
(c) Give examples of fat soluble vitamins.
(d) The two strands in DNA are not identical but are complementary. Explain.
(e) Write uses of B-Complex.
(f) Name the disaccharide which on hydrolysis gives two molecules of glucose.
(g) Name purines present in DNA?
→
Explain the methods of preparation alcohol from the following compounds:
(a) From carbonyl compound
(b) From carboxylic acid
(c) From esters
(d) From Grignard reagent
→