PUC Science 2nd PUC Class 12 - Karnataka Board PUC Question Bank Solutions

Account for the following: Oxygen shows catenation behavior less than sulphur.

Give a simple chemical test to distinguish between the following pair of compounds:

Ethanal and Propanal

Write the final product(s) in each of the following reactions:

Give reasons: SO₂ is reducing while TeO₂ is an oxidising agent.

Distinguish between:

C₆H₅-COCH₃ and C₆H₅-CHO

Distinguish between: CH3COOH and HCOOH

A and B are two functional isomers of compound C₃H₆O.On heating with NaOH and I₂, isomer B forms yellow precipitate of iodoform whereas isomer A does not form any precipitate. Write the formulae of A and B.

Using the E° values of A and B, predict which is better for coating the surface of iron [E°(Fe⁺²/Fe) = -0.44V] to prevent corrosion and why?

Given: E° (A⁺²/A)=-2.37 V: E°(B⁺²/B)= -0.14V

Following reactions occur at cathode during the electrolysis of aqueous sodium chloride solution:

Na+(aq) + e⁻ ⟶ Na (s) E⁰ =  2.71 V

H+(aq) + e⁻ ⟶ `1/2`  H₂ (g) E⁰ = 0.00 V

On the basis of their standard reduction electrode potential (E⁰) values, which reaction is feasible at the cathode and why?

Reduction of metal oxide to metal becomes easier if the metal obtained is in liquid state. Why?

[NiCl₄]²⁻ is paramagnetic, while [Ni(CO)₄] is diamagnetic, though both are tetrahedral. Why? (Atomic number of Ni = 28)

It is necessary to remove CO when ammonia is prepared by Haber's process.

Predict the products of the following reactions :

The presence of nitro group (−NO₂) at o/p positions increases the reactivity of haloarenes towards nucleophilic substitution reactions.

Account for the following : There is large difference between the melting and boiling points of oxygen and sulphur.

Give a simple chemical test to distinguish between the following pair of compounds :

(CH₃)₂NH and (CH₃)₃N

Write the dispersed phase and dispersion medium of butter.

Give reasons for the following : H₂Te is the strongest reducing agent amongst all the hydrides of Group 16 elements.

Give a simple chemical test to distinguish between the following pair of compounds :

CH₃CH₂CHO and CH₃CH₂COCH₃

What is the role of zinc metal in the extraction of silver ?