12th Chemistry Paper Solutions Set 1 : CBSE Delhi Previous Year 2007

General Instructions:
(i) All questions are compulsory.
(ii)  This question paper consists of four sections A, B, C and D. 
Section A contains 5 questions of one mark each.
Section B is of 7 questions of two marks each.
Section C is of 12 questions of three marks each and
Section D is of 3 questions of five marks each.
(iii) There is no overall choice. However, an internal choice has been provided.
(iv) Wherever necessary, the diagrams drawn should be neat and properly labelled.
Q1 :

What is the number of atoms per unit cell in a body-centred cubic structure?


Answer :

The number of atoms per unit cell in a body-centred cubic structure is 2 (8 corner atoms x atom per unit cell + 1 body-centre atom).

Q2 :

Define osmotic pressure.


Answer :

Osmotic pressure is defined as the equilibrium hydrostatic pressure set up by a difference between the concentrations of solutions on the two sides of a semi-permeable membrane. Experimentally, it has been found that for a dilute solution, osmotic pressure (π) is proportional to the molarity (C) of the solution at a given temperature (T).

π = CRT

Where, R is the gas constant

Or, [n →Moles of the solute, V →Volume of solution]

Or, [, w2 →Mass of solute, M2 →Molar mass of solute]

Q3 :

For the reaction

the rate law is expressed as

rate = k[Cl2][NO]2

What is the overall order of this reaction?


Answer :

Overall order of this reaction = 1 + 2

= 3

Q4 :

Write the IUPAC name of the compound:


Answer :

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Q5 :

Why do nitro compounds have high boiling points in comparison with other compoundsof same molecular mass?


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Q6 :

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.


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Q7 :

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


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Q8 :

Write balanced chemical equations for the following reactions:

(i) Aluminium dissolves in aqueous hydrochloric acid

(ii) Tin reacts with a hot alkali solution


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Q9 :

Write the structuresof the following species:

(i) H3PO2 (ii) H2SO5


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Q10 :

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

(i)

(ii)


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Q11 :

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.


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Q12 :

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

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


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Q13 :

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

and O2.


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Q14 :

Explain each of the following with a suitable example:

(i) Paramagnetism

(ii) Piezoelectric effect

(iii) Frenkel defect in crystals


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Q15 :

In the production of water gas the reaction involved is:

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

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


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Q16 :

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?


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Q17 :

The decomposition of NH3on platinum surface, is a zero order reaction with k= 2.5 x 10-4M s-1. What are the rates of production of N2and H2?


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Q18 :

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.


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Q19 :

How wouldyou 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.


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Q20 :

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]


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Q21 :

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

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


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Q22 :

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


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Q23 :

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.


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Q24 :

(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.


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Q25 :

(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) K2Cr2O7from Na2CrO4

(ii) KMnO4from 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?


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Q26 :

(a) Calculate the emf of the cell

Mg(s) | Mg2+(0.1M) || Cu2+(1 × 10−3M) | 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 × 10−3S cm−1?

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

A solution of H2SO4with platinum electrodes.


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Q27 :

(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


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12th Chemistry Paper Solutions Set 3 : CBSE Delhi Previous Year 2013 will be available online in PDF book soon. The solutions are absolutely Free. Soon you will be able to download the solutions.