Class 12 Chemistry 2018 Board Exam

Write the coordination number and oxidation state of Platinum in the complex [Pt(en)₂Cl₂].

Out of chlorobenzene and benzyl chloride, which one gets easily hydrolysed by aqueous NaOH and why ?

Write the IUPAC name of the following :

        CH₃
         |
CH₃ – C – CH – CH₃
        |       |
       C₂H₅   OH

Calculate the freezing point of a solution containing 60 g of glucose (Molar mass = 180 g mol⁻¹) in 250 g of water.
(Kf of water = 1·86 K kg mol⁻¹)

For the reaction
2N₂O₅ (g) 4NO₂ (g) + O₂ (g),
the rate of formation of NO₂ (g) is 2·8 10⁻³ M s⁻¹. Calculate the rate of disappearance of N₂O₅ (g).

How do you convert the following ?
(a) Ethanal to Propanone
(b) Toluene to Benzoic acid

OR

Account for the following :
(a) Aromatic carboxylic acids do not undergo Friedel-Crafts reaction.
(b) pKa value of 4-nitrobenzoic acid is lower than that of benzoic acid.

Complete and balance the following chemical equations :
(a) Fe²⁺ + MnO₄– + H⁺
(b) MnO₄– + H₂O + I⁻

Give reasons for the following :
(a) Measurement of osmotic pressure method is preferred for the determination of molar masses of macromolecules such as proteins and polymers.
(b) Aquatic animals are more comfortable in cold water than in warm water.
(c) Elevation of boiling point of 1 M KCl solution is nearly double than that of 1 M sugar solution.

A first order reaction is 50% completed in 40 minutes at 300 K and in 20 minutes at 320 K. Calculate the activation energy of the reaction.
(Given : log 2 = 0·3010, log 4 = 0·6021, R = 8·314 JK⁻¹ mol⁻¹)

Give reasons :
(a) E° value for Mn³⁺/Mn²⁺ couple is much more positive than that for Fe³⁺/Fe²⁺.
(b) Iron has higher enthalpy of atomization than that of copper.
(c) Sc³⁺ is colourless in aqueous solution whereas Ti³⁺ is coloured.