Board Paper of Class 12-Science 2007 Chemistry (SET 1) - Solutions

State ‘Pauli’s exclusion principle’. Explain giving an example how this principle limits the maximum occupancy of an energy level in an atom.

OR

State ‘Aufbau principle’ and give the order in which the energies of orbitals increase and hence they are filled in that order.

A reaction with, always has an equilibrium constant value greater than 1. Why? 

Write balanced chemical equations for the following reactions:

(i) Aluminium dissolves in aqueous hydrochloric acid

(ii) Tin reacts with a hot alkali solution

Write the structures of the following species:

(i) H₃PO₂ (ii) H₂SO₅

Identify whether the following pairs of compounds are structural or geometrical isomers:

(i)

(ii)

How would you account for the following:

(i) Phenols are much more acidic than alcohols.

(ii) The boiling points of ethers are much lower than those of the alcohols of comparable molar masses.

Draw the structure of the monomer of each of the following polymers:

(i) Polyvinylchloride (PVC) (ii) Nylon-6

Write the molecular orbital configurations of the following species and rearrange them in the increasing order of their bond lengths:

and O₂.

Explain each of the following with a suitable example:

(i) Paramagnetism

(ii) Piezoelectric effect

(iii) Frenkel defect in crystals

In the production of water gas the reaction involved is:

C(s) + H₂O(g) →CO(g) + H₂(g), Δ_rH°= +131.4 kJ mol⁻¹

For this reaction, Δ_rS°is +134 JK⁻¹mol⁻¹. Find out the spontaneous feasibility of this reaction at (i) 25°C and (ii) 1000°C.

An antifreeze solution is prepared from 222.6 g of ethylene glycol [C₂H₄(OH)₂] and 200 g of water. Calculate the molality of the solution. If the density of this solution be 1.072 g mL⁻¹, what will be the molarity of the solution?

The decomposition of NH₃ on platinum surface, is a zero order reaction with k = 2.5 × 10⁻⁴ M s⁻¹. What are the rates of production of N₂ and H₂?

Explain the following terms giving a suitable example in each case:

(i) Emulsification

(ii) Homogeneous catalysis

OR

Define adsorption. Write any two features which distinguish physisorption from chemisorption.

How would you account for the following?

(i) The lower oxidation state becomes more stable with increasing atomic number in Group 13.

(ii) Hydrogen fluoride is much less volatile than hydrogen chloride.

(iii) Interhalogen compounds are strong oxidising agents.

Write the name and draw the structure of each of the following complex compounds:

(i) [Co(NH₃)₄ (H₂O)₂]Cl₃

(ii) [Pt(NH₃)₄] [NiCl₄]

The net nuclear reaction of a radioactive decay series is written as:

Write three pieces of information that you get from the above equation.

Give chemical tests to distinguish between the following pairs of compounds:

(i) Propanal and propanone

(ii) Methyl acetate and ethyl acetate

(iii) Benzaldehyde and benzoic acid

How would you achieve the following conversions:

(i) Nitrobenzene to aniline

(ii) An alkyl halide to a quaternary ammonium salt

(iii) Aniline to benzonitrile

Write the chemical equation with reaction conditions in each case.

(i) Give an example of a hybrid propellant.

(ii) What are acid dyes?

(iii) Name a food preservative which is most commonly used by food producers.

(a) Describe the general trends in the following properties of the first series of the transition elements:

(i) Stability of +2 oxidation state

(ii) Formation of oxometal ions

(b) Assign reason for each of the following:

(i) Transition elements exhibit variable oxidation states

(ii) Transition metal ions are usually coloured

OR

(a) Write the steps involved in the preparation of:

(i) K₂Cr₂O₇ from Na₂CrO₄

(ii) KMnO₄ from K₂MnO₄

(iii) Calomel from corrosive sublimate

(b) What is meant by lanthanoid contraction? What effect does it have on the chemistry of the elements which follow lanthanoids?

(a) Calculate the emf of the cell

Mg(s) | Mg²⁺ (0.1M) || Cu²⁺ (1 × 10⁻³ M) | Cu (s)

Given: E° Cu²⁺/Cu = +0.34V, E° Mg²⁺/Mg = −2.37 V

(b) Explain with examples the terms weak and strong electrolytes.

OR

(a) The resistance of a conductivity cell containing 0.001 M KC1 solution at 298 K is 1500 Ω. What is the cell constant if the conductivity of 0.001 M KCl solution at 298 K is 0.146 × 10⁻³ S cm⁻¹?

(b) Predict the products of electrolysis in the following:

A solution of H₂SO₄ with platinum electrodes.

(a) Name the three major classes of carbohydrates and give an example of each of these classes.

(b) Answer the following:

(i) What type of linkage is responsible for the primary structure of proteins?

(ii) Name the location where protein synthesis occurs in our body.

OR

(a) How are lipids classified? Give an example of each class.

(b) Explain the following terms:

(i) Mutarotation

(ii) Avitaminosis