Board Paper of Class 12-Science 2009 Chemistry (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
Which point defect in crystals does not affect the density of the relevant solid?VIEW SOLUTION
- Question 2
Define the term ‘Tyndall effect’.VIEW SOLUTION
- Question 3
Why is the froth flotation method selected for the concentration of sulphide ores?VIEW SOLUTION
- Question 4
Why is Bi (V) a stronger oxidant than Sb (V)?VIEW SOLUTION
- Question 5
Give the IUPAC name of the following compound:
- Question 6
Write the structure of 3-oxopentanal.VIEW SOLUTION
- Question 7
Why is an alkylamine more basic than ammonia?VIEW SOLUTION
- Question 8
Give an example of elastomer.VIEW SOLUTION
- Question 9
A reaction is of second order with respect to a reactant. How will the rate of reaction be affected if the concentration of this reactant is
(ii) Reduced to half?VIEW SOLUTION
- Question 10
Explain the role of
(i) Cryolite in the electrolytic reduction of alumina.
(ii) Carbon monoxide in the purification of nickel.VIEW SOLUTION
- Question 11
Draw the structures of the following molecules:
(ii) BrF3VIEW SOLUTION
- Question 12
Complete the following chemical reaction equations:
- Question 13
Differentiate between molality and molarity of a solution. What is the effect of change in temperature of a solution on its molality and molarity?VIEW SOLUTION
- Question 14
Which ones in the following pairs of substances undergoes SN2 substitution reaction faster and why?
- Question 15
Complete the following reaction equations:
- Question 16
Explain what is meant by
(i) A peptide linkage
(ii) A glycosidic linkageVIEW SOLUTION
- Question 17
Name two water soluble vitamins, their sources and the diseases caused due to their deficiency in diet.VIEW SOLUTION
- Question 18
Draw the structures of the monomers of the following polymers:
What is the repeating unit in the condensation polymer obtained by combining HO2CCH2CH2CO2H (succinic acid) and H2NCH2CH2NH2 (ethylene diamine)?VIEW SOLUTION
- Question 19
Iron has a body-centred cubic unit cell with a cell edge of 286.65 pm. The density of iron is 7.87 g cm−3. Use this information to calculate Avogadro’s number.
(At. Mass of Fe = 56 g mol−1)VIEW SOLUTION
- Question 20
100 mg of a protein is dissolved in just enough water to make 10.0 mL of solution. If this solution has an osmotic pressure of 13.3 mm Hg at 25°C, what is the molar mass of the protein?
(R = 0.0821 L atm mol−1 K−1 and 760 mm Hg = 1 atm)VIEW SOLUTION
- Question 21
A first-order reaction has a rate constant of 0.0051 min−1. If we begin with 0.10 M concentration of the reactant, what concentration of reactant will remain in the solution after 3 hours?VIEW SOLUTION
- Question 22
How are the following colloids different from each other with respect to dispersion medium and dispersed phase? Give one example of each type.
(i) An aerosol (ii) A hydrosol (iii) An emulsionVIEW SOLUTION
- Question 23
Account for the following:
(i) NH3 is a stronger base than PH3.
(ii) Sulphur has a greater tendency for catenation than oxygen.
(iii) Bond dissociation energy of F2 is less than that of Cl2.
Explain the following situations:
(i) In the structure of HNO3 molecule, the N − O bond (121 pm) is shorter than the N − OH bond (140 pm).
(ii) SF4 is easily hydrolysed whereas SF6 is not easily hydrolysed.
(iii) XeF2 has a straight linear structure and not a bent angular structure.VIEW SOLUTION
- Question 24
For the complex [Fe(en)2Cl2] Cl, (en = ethylene diamine), identify
(i) The oxidation number of iron,
(ii) The hybrid orbitals and the shape of the complex,
(iii) The magnetic behaviour of the complex,
(iv) The number of geometrical isomers,
(v) Whether there is an optical isomer also, and
(vi) Name of the complex. (At. No. of Fe = 26)VIEW SOLUTION
- Question 25
Explain the mechanism of the following reactions:
(i) Addition of Grignard’s reagent to the carbonyl group of a compound forming an adduct followed by hydrolysis.
(ii) Acid catalysed dehydration of an alcohol forming an alkene.
(iii) Acid catalysed hydration of an alkene forming an alcohol.VIEW SOLUTION
- Question 26
Giving an example for each, describe the following reactions:
(i) Hofmann’s bromamide reaction
(ii) Gatterman reaction
(iii) A coupling reactionVIEW SOLUTION
- Question 27
Explain the following types of substances with one suitable example, for each case:
(i) Cationic detergents
(ii) Food preservatives
(iii) AnalgesicsVIEW SOLUTION
- Question 28
(a) Define molar conductivity of a substance and describe how for weak and strong electrolytes, molar conductivity changes with concentration of solute. How is such change explained?
(b) A voltaic cell is set up at 25°C with the following half cells:
Ag+ (0.001 M) | Ag and Cu2+ (0.10 M) | Cu
What would be the voltage of this cell?
(a) State the relationship amongst the cell constant of a cell, the resistance of the solution in the cell and the conductivity of the solution. How is molar conductivity of a solute related to the conductivity of its solution?
(b) A voltaic cell is set up at 25°C with the following half-cells:
Al | Al3+ (0.001 M) and Ni | Ni2+ (0.50 M)
Calculate the cell voltage.
- Question 29
(a) Complete the following chemical reaction equations:
(b) Explain the following observations about the transition/inner transition elements:
(i) There is in general an increase in density of element from titanium (Z = 22) to copper (Z = 29).
(ii) There occurs much more frequent metal−metal bonding in compounds of heavy transition elements (3rd series).
(iii) The members of the actinoid series exhibit a larger number of oxidation states than the corresponding members of the lanthanoid series.
(a) Complete the following chemical equations for reactions:
(b) Give an explanation for each of the following observations:
(i) The gradual decrease in size (actinoid contractions) from element to element is greater among the actinoids than among the lanthanoids (lanthanoid contraction).
(ii) The greatest number of oxidation states are exhibited by the members in the middle of a transition series.
(iii) With the same d-orbital configuration (d4) Cr2+ ion is a reducing agent but Mn3+ ion is an oxidising agent.VIEW SOLUTION
- Question 30
(a) Illustrate the following name reactions by giving example:
(i) Cannizzaro’s reaction
(ii) Clemmensen reduction
(b) An organic compound A contains 69.77% carbon, 11.63% hydrogen and rest oxygen. The molecular mass of the compound is 86. It does not reduce Tollen’s reagent but forms an addition compound with sodium hydrogen sulphite and gives positive iodoform test. On vigorous oxidation it gives ethanoic and propanoic acids. Derive the possible structure of compound A.
(a) How are the following obtained?
(i) Benzoic acid from ethyl benzene
(ii) Benzaldehyde from toluene
(b) Complete each synthesis by giving the missing material, reagent or products: