Give reasons:
(i) Thermal stability decreases from H₂O to H₂Te.
(ii) Fluoride ion has higher hydration enthalpy than chloride ion.
(iii) Nitrogen does not form pentahalide.

Give reasons :
(i) Acetylation of aniline reduces its activation effect.
(ii) CH₃NH₂ is more basic than C₆H₅NH₂.
(iii) Although –NH₂ is o/p directing group, yet aniline on nitration gives a significant amount of m-nitroaniline.

After watching a programme on TV about the presence of carcinogens(cancer causing agents) Potassium bromate and Potassium iodate in bread and other bakery products, Ritu a class XII student decided to aware others about the adverse effects of these carcinogens in foods. She consulted the school principal and requested him to instruct canteen contractor to stop selling sandwiches, pizza, burgers and other bakery products to the students. Principal took an immediate action and instructed the canteen contractor to replace the bakery products with some proteins and vitamins rich food like fruits, salads, sprouts etc. The decision was welcomed by the parents and students.

After reading the above p

(a) Account for the following:
(i) Transition metals form a large number of complex compounds.
(ii) The lowest oxide of transition metal is basic whereas the highest oxide is amphoteric or acidic.
(iii) E0 value for the Mn³⁺/Mn²⁺ couple is highly positive (+1.57 V) as compare to Cr³⁺/Cr²⁺.
(b) Write one similarity and one difference between the chemistry of lanthanoid and actinoid elements.
OR
(a) (i) How is the variability in oxidation states of transition metals different from that of the p-block elements ?
(ii) Out of Cu⁺ and Cu²⁺, which ion is unstable in aqueous solution and why ?
(iii)

(a) An element has atomic mass 93 g/mol and density 11.5 g /cm³. If the edge length of its unit cell is 300 pm, identify the type of unit cell.

(b) Write any two differences between amorphous solids and crystalline solids.
Or
(a) Calculate the number of unit cells in 8.1 g of aluminium if it crystallizes in a f.c.c. structure. (Atomic mass of Al = 27 g/ mol)
(b) Give reasons :
(i) In stoichiometric defects, NaCl exhibits Schottky defect and not Frenkel defect.
(ii) Silicon on doping with Phosphorus forms n-type semiconductor.
(iii) Ferrimagnetic substances show better magnetism than antiferromagnetic substan

Write the product(s) in the following reactions :

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(b) Give simple chemical tests to distinguish between the following pairs of compounds :
(i) Ethanol and Phenol
(ii) Propanol and 2-methylpropan-2-ol



Or
(a) Write the formula of reagents used in the following reactions :
(i) Bromination of phenol to 2,4,6-tribromophenol
(ii) Hydroboration of propene and then oxidation to propanol.