12th Chemistry Paper Solutions Set 1 : CBSE Abroad 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 :

Find out the number of atoms per unit cell in a face-centred cubic structure having only single atoms at its lattice points.


Answer :

Calculation of the number of atoms per unit cell in a face-centred cubic structure

Contribution by atoms at the corners =

Contribution by atoms on the faces =

Number of atoms present in the unit cell = 1 + 3 = 4

Q2 :

State the condition resulting in reverse osmosis.


Answer :

Reverse osmosis will occur if a pressure higher than the osmotic pressure is applied on the solution.

Q3 :

Express the rate of the following reaction in terms of disappearance of hydrogen in the reaction.


Answer :

In terms of disappearance of hydrogen in the reaction, the rate of reaction is .

Q4 :

Name the following compound according to IUPAC system:


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Q5 :

Why do amines react as nucleophiles?


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Q6 :

(a) Write the mathematical expression for the relationship of the wavelength (λ) of a moving particle and its momentum (P)

(b) What physical meaning is attributed to the square of the absolute value of wave function, ?

OR

State the Heisenberg Uncertainty Principle and explain as to why it is not of real consequence when applied to a macroscopic object, like a cricket ball.


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Q7 :

Define Conductivity and molar conductivity for the solution of an electrolyte.


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Q8 :

How would you account for the following?

(i) Sulphur hexafluoride is less reactive than sulphur tetrafluoride.

(ii) Of the noble gases only xenon forms known chemical compounds.


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Q9 :

On the basis of the standard electrode potential values stated for acid solution, predict whether Ti4+species may be used to oxidise FeIIto FeIII


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Q10 :

What are chiral objects? Indicate the presence of centre of chirality, if any, in the molecules of 3-bromopent-1-ene.


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Q11 :

How may the following conversions be carried out?

(i) Propene to propan-2-ol

(ii) Anisole to phenol

(Write the reaction only).


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Q12 :

Write formulae of the monomers of polythene and Teflon.


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Q13 :

Define bond order in a diatomic molecule. Find the bond order in O2molecule. State and explain magnetic character of molecular oxygen.


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Q14 :

Assign reasons for the following:

(i) Phosphorus-doped silicon is a semiconductor.

(ii) Schottky defect lowers the density of a solid.

(iii) Some of the very old glass objects appear slightly milky instead of being transparent.


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Q15 :

A 0.1539 molal aqueous solution of cane sugar (mol.mass = 342 g mol−1) has a freezing point of 271 K while the freezing point of pure water is 273.15 K. What will be the freezing point of an aqueous solution containing 5 g of glucose (mol. mass = 180 g mol−1) per 100 g of solution?


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Q16 :

Calculate the standard cell potential of the galvanic cell in which the following reaction takes place:

Also calculate the ΔrG Θvalue of the reaction.

(Given and F = 96500 C mol-1)


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Q17 :

The rate constant for a first-order reaction is 60 s−1. How much time will it take to reduce the concentration of the reactant to 1/10thof its initial value?


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Q18 :

Describe the following types of colloids, giving an example for each:

(i) Multimolecular colloids

(ii) Macromolecular colloids

OR

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

(i) Shape-selective catalysis

(ii) Dialysis


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Q19 :

How would you account for the following?

(i) The transition elements have high enthalpies of atomisation.

(ii) The transition metals and their compounds are found to be good catalysts in many processes.


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Q20 :

Describe for any twoof the following complex ions, the type of hybridisation, shape and magnetic property:

(i)

(ii)

(iii)


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Q21 :

Complete the following statements for nuclear reactions:

(i)

(ii)

(iii)

(Note: You may use ‘X’ as symbol if the correct symbol in a reaction is not known)


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Q22 :

Write one chemical equation for each, to illustrate the following reactions:

(i) Rosenmund reduction

(ii) Cannizzaro reaction

(iii) Fischer esterification


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Q23 :

Account for any twoof the following

(a) Amines are basic substances while amides are neutral.

(b) Nitro compounds have higher boiling points than the hydrocarbons having almost the same molecular mass.

(c) Aromatic amines are weaker bases than aliphatic amines.


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Q24 :

(a) Describe and illustrate with an example each, a mordant dye and a detergent,

(b) Give an example of a liquid propellant.


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Q25 :

(a) Prove that ΔGsystem= - TΔStotalfor a system which is not isolated.

(b) The decomposition of Fe2O3is a non-spontaneous process

Show that the reduction of Fe2O3by CO can be made spontaneous by coupling with the following reaction:

OR

(a) Define the following terms:

(i) Entropy

(ii) A spontaneous process

(b) Given below are the standard Gibbs energy changes for two reactions at 1773 K:

Discuss the possibility of reducing Al2O3with carbon at this temperature. Given that:


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Q26 :

(a) Assign reasons for the following:

(i) PbO2is a stronger oxidising agent than SnO2

(ii) In solid state PCl5behaves as an ionic species,

(iii) Aluminium chloride (AlCl3) is very often used as a catalyst.

(b) What is the structural difference between orthosilicates and pyrosilicates?

OR

(a) Assign reasons for the following:

(i) The acid strengths of acids increase in the order

HF < HCl < HBr < HI

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

(iii) H3PO2behaves as a monoprotic acid.

(b) Draw the structures of the following compounds:

(i) SF4

(ii) XeF2


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Q27 :

(a) Answer the following question briefly:

(i) What are reducing sugars?

(ii) What is meant by denaturation of a protein?

(iii) How is oxygen replenished in our atmosphere?

(b) Define enzymes.

OR

(a) Answer the following questions briefly:

(i) What are any two good sources of vitamin A?

(ii) What are nucleotides?

(iii) Give an example of simple lipids.

(b) How are carbohydrates classified?


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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.