Board Paper of Class 12-Science 2008 Chemistry Delhi(SET 1) - Solutions
(i) All questions are compulsory
(ii) Question numbers 1 to 8 are very short-answer questions and carry 1 mark each.
(iii) Question numbers 9 to 18 are short-answer questions and carry 2 marks each.
(iv) Question numbers 19 to 27 are also short-answer questions and carry 3 marks.
(v) Question numbers 28 to 30 are long-answer questions and carry 5 marks each.
(vi) Use Log Tables, if necessary. Use of calculators is not allowed.
- Question 1
What is the coordination number of each type of ions in a rock-salt type crystal structure?VIEW SOLUTION
- Question 2
Define the term ‘order of reaction’ for chemical reactions.VIEW SOLUTION
- Question 3
What causes Brownian movement in a colloidal solution?VIEW SOLUTION
- Question 4
In which one of the two structures, and , the bond angle has a higher
- Question 5
Write the IUPAC name of the following compound:
- Question 6
Arrange the following compounds in an increasing order of their acid strengths:
(CH3)2CHCOOH, CH3CH2CH(Br)COOH, CH3CH(Br)CH2COOHVIEW SOLUTION
- Question 7
Write a chemical reaction in which the iodide ion replaces the diazonium group in a diazonium salt.VIEW SOLUTION
- Question 8
Name a substance that can be used as an antiseptic as well as a disinfectant.VIEW SOLUTION
- Question 9
Explain as to why haloarenes are much less reactive than haloalkanes towards nucleophilic substitution reactions.
Which compound in each of the following pairs will react faster in SN2 reaction with −OH? Why?
(i) CH3Br or CH3I
(ii) (CH3)3CCl or CH3ClVIEW SOLUTION
- Question 10
(a) State the IUPAC name of the following compound:
(b) Complete the following chemical equation:
CH3CH2CH=CH2 + HBrVIEW SOLUTION
- Question 11
State Henry’s law correlating the pressure of a gas and its solubility in a solvent and mention two applications for the law.VIEW SOLUTION
- Question 12
A first order decomposition reaction takes 40 minutes for 30% decomposition. Calculate its value.VIEW SOLUTION
- Question 13
What is meant by the ‘rate constant, k’ of a reaction? If the concentration be expressed in mol L−1 units and time in seconds, what would be the units for k (i) for a zero-order reaction and (ii) for a first-order reaction?VIEW SOLUTION
- Question 14
Define the following terms in relation to proteins:
(i) Peptide linkage
(ii) DenaturationVIEW SOLUTION
- Question 15
List the reactions of glucose which cannot be explained by its open-chain structure.VIEW SOLUTION
- Question 16
Assign a reason for each of the following statements:
(i) Ammonia is a stronger base than phosphine.
(ii) Sulphur in vapour state exhibits a paramagnetic behaviour.VIEW SOLUTION
- Question 17
Draw the structure of the following molecules:
(ii) XeF4VIEW SOLUTION
- Question 18
What are biodegradable and non-biodegradable detergents? Give one example of each class.VIEW SOLUTION
- Question 19
What is semiconductor? Describe the two main types of semiconductors and explain mechanisms for their conduction.VIEW SOLUTION
- Question 20
Calculate the temperature at which a solution containing 54 g of glucose, (C6H12O6), in 250 g of water will freeze.
(Kf for water = 1.86 K mol−1 kg)VIEW SOLUTION
- Question 21
What are lyophilic and lyophobic sols? Give one example of each type. Which one of these two types of sols is easily coagulated and why?VIEW SOLUTION
- Question 22
State briefly the principles which serve as basis for the following operations in metallurgy:
(i) Froth floatation process
(ii) Zone refining
(iii) Refining by liquationVIEW SOLUTION
- Question 23
Write chemical equations for the following processes:
(i) Chlorine reacts with a hot concentrated solution of sodium hydroxide
(ii) Orthophosphorous acid is heated
(iii) PtF6 and xenon are mixed together
Complete the following chemical equations:
(i) Ca3P2(s) + H2O(l) →……..
(iii) F2(g) + H2O(l) →……..VIEW SOLUTION
- Question 24
(a) What is a ligand? Give an example of a bidentate ligand.
(b) Explain as to how the two complexes of nickel, [Ni(CN)4]2− and Ni(CO)4, have different structures but do not differ in their magnetic behaviour. (Ni = 28)VIEW SOLUTION
- Question 25
Name the reagents which are used in the following conversions:
(i) A primary alcohol to an aldehyde
(ii) Butan-2-one to butan-2-ol
(iii) Phenol to 2, 4, 6-tribromophenolVIEW SOLUTION
- Question 26
Account for the following observations:
(i) pKb for aniline is more than that for methylamine.
(ii) Methylamine solution in water reacts with ferric chloride solution to give a precipitate of ferric hydroxide.
(iii) Aniline does not undergo Friedel-Crafts reaction.VIEW SOLUTION
- Question 27
Write the names and structures of the monomers of the following polymers:
(iii) Nylon-6VIEW SOLUTION
- Question 28
Conductivity of 0.00241 M acetic acid solution is 7.896 × 10−5 S cm−1. Calculate its molar conductivity in this solution. If for acetic acid be 390.5 S cm2 mol−1, what would be its dissociation constant?
Three electrolytic cells A, B and C containing solutions of zinc sulphate, silver nitrate and copper sulphate respectively, are connected in series. A steady current of 1.5 ampere was passed through them until 1.45 g of silver was deposited at the cathode of cell B. How long did the current flow? What mass of copper and what mass of zinc were deposited in the concerned cells?
(Atomic masses of Ag = 108, Zn = 65.4, Cu = 63.5)VIEW SOLUTION
- Question 29
Assign reasons for the following:
(i) The enthalpies of atomisation of transition elements are high.
(ii) The transition metals and many of their compounds act as good catalyst.
(iii) From element to element the actinoid contraction is greater than the lanthanoid contraction.
(iv) The E0 value for the Mn3+/Mn2+ couple is much more positive than that for Cr3+/Cr2+.
(v) Scandium (Z = 21) does not exhibit variable oxidation states and yet it is regarded as a transition element.
(a) What may be the possible oxidation states of the transition metals with the following d electronic configurations in the ground state of their atoms:
3d34s2, 3d54s2 and 3d64s2
Indicate relative stability of oxidation states in each case.
(b) Write steps involved in the preparation of (i) Na2CrO4 from chromite ore and (ii) K2MnO4 from pyrolusite ore.VIEW SOLUTION
- Question 30
(a) Complete the following reaction statements by giving the missing starting material, reagent or product as required:
(b) Describe the following reactions:
(i) Cannizaro reaction
(ii) Cross aldol condensation
(a) How would you account for the following:
(i) Aldehydes are more reactive than ketones towards nucleophiles.
(ii) The boiling points of aldehydes and ketones are lower than those of the corresponding acids.
The aldehydes and ketones undergo a number of addition reactions.
(b) Give chemical tests to distinguish between:
(i) Acetaldehyde and benzaldehyde
(ii) Propanone and propanolVIEW SOLUTION