HSC Chemistry SAMPLE PAPER-3

HSC Chemistry SAMPLE PAPER-3

Section A

1. Select and write the correct answers to the following questions:

(i)

shows which type of defect?
(a) Frenkel.
(b) Schottky
(c) Both (a) and (b)
(d) Impurity defect

(ii) Nylon fibres are:
(a) Semisynthetic fibres
(b) Polyamide fibres
(c) Polyester fibres
(d) Cellulose fibres

(iii) A gas is allowed to expand in a well insulated container against a constant external pressure of 2.5 Bar from an initial volume of to a final volume of 4.5L The change in internal energy, of the gas will be
(a)
(b)
(c)
(d)

(iv) The formula for the Grignard’s reagent is:
(a)
(b)
(c)
(d)

(v) Which of the following substrate will give ionic organic product on reaction?

(a)

(b)

(c)

(d)

(vi) Which of the following solution will have value equal to 1.0 ?

(a) of of

(b) of of

(c) of of

(d) of of

(vii) Which of the following is not correct?

(a) Gibbs energy is an extensive property

(b) Electrode potential or cell potential is an intensive property

(c) Electrical work

(d) If half reaction is multiplied by a numerical factor, the corresponding value is also multiplied by the same factor. (viii) The oxidation state of cobalt ion in the complex is
(a) +2
(b) +3
(c) +1
(d) +4

(ix) Open chain formula of glucose does not contain

(a) Formyl group

(b) Anomeric hydroxyl group

(c) Primary hydroxyl group

(d) Secondary hydroxyl group

(x) Which of the following has highest electron gain enthalpy?
(a) Fluorine
(b) Chlorine
(c) Bromine
(d) lodine

2. Answer the following questions:

(i) The boiling point of solution containing of substance in of water is higher by 0.0512 than the boiling point of pure water. The molar mass of substance is………..

(ii) Name one amphoteric solvent.

(iii) What is denaturation of Proteins?

(iv) Why cations are lewis acids?

(v) What is the relationship between coefficients of reactants in a balanced equation for an overall reaction and exponents in rate law? In what case the coefficients are the exponents?

(vi) Which amide does produce ethanamine by Hofmann bromamide degradation reaction?

(vii) Comment on the statement: no work is involved in an Expansion of gas in vacuum.

(viii) Write the electrode reactions during electrolysis of molten .

40. Section B

41. Attempt any Eight of the following questions:

3. Which nanomaterial is used in sunscreen lotion? Write its use.
4. Construct a Galvanic cell the electrodes and . Calculate
5. What is diazotisation? Write diazotisation reaction of aniline.
6. Why alkyl halides though polar are immiscible with water?
7. The half life of a first order reaction is 1.7 Hours. How long will it take for of the reactant to react?
8. What are isotonic and hypertonic solutions?
9. Give full form of the following names: . XRD b. TEM
10. Draw a neat diagram for the Zwitterion ion.
11. What are ionisation isomers? Give an example.
12. Write reaction showing conversion of ethanenitrile into ethanol.
13. Give the reactions involved in the Etard’s reaction.
14. Reactions involving Grignard reagent must be carried out under anhydrous condition.

42. Section C

43. Attempt any Eight of the following questions:

15. Give two examples which undergo Wolf-Kishner reduction
16. Fish generally needs concentration in water at least for survival. What partial pressure of above the water is needed for the survival of fish? Given the solubility of in water at and partial pressure is ) .
17. Write the names and structural formulae of oxoacids of chlorine.
18. Write a note on Cannizaro reaction.
19. Derive the expression for the maximum work.
20. Calculate emf of the following cell at .

21. What is the action of the following reagents on toluene? (i) Alkaline , dil. and heat

(ii) in

(iii) Acetyl chloride in presence of anhydrous .

22. Calculate the standard enthalpy of the reaction,

(graphite) from the following reactions:

(i)

(ii) (graphite)

(iii) graphite)

23. Give the similarites and differences in elements of and series.
24. How will you represent first order reactions graphically.
25. What are synthetic fibers? How is terylene prepared?
26. Give the steps to understand the metal-ligand bonding.

44. Section D

45. Attempt any Three of the following questions:

27. Explain trends in ionisation enthalpies of -block elements.
28. Give the properties of Lanthanoids.
29. What are cationic, anionic and neutral complexes? Give one example of each..
30. Explain the relation between lonic product and solubility product to predict whether a precipitate will form when two solutions are mixed?
31. Describe the manufacturing of by contact process.

46. [A] Answer Key

47. Section A

1. (i) (c) (c) Both (a) and (b)

(ii) (b) Polyamide fibres

(iii) (a)

(iv) (a)

(v) (a)

(vi) (d) of of

(vii) (d) If half reaction is multiplied by a numerical factor. the corresponding value is also multiplied by the same factor.

(viii) (b) +3

(ix) (b) Anomeric hydroxyl group

(x) (b) Chlorine

2.

wt of solute

wt. of solvent

(ii) Water

(iii) Denaturation is the process by which the molecular shape of protein changes without breaking the amide/ peptide bonds that form the primary structure. e.g. Boiling of egg coagulates egg white and conversion of milk into curd. (iv) Cations are electron-deficient species and can accept an electron pair. Hence, cations are Lewis acids.

(v) Coefficients of reactants in a balanced chemical equation may or may not be the same as the exponents in rate law for the same reaction. For elementary reaction, coefficients in a balanced chemical equation are the same as the exponents in the rate law.

(vi) Propanamide produces ethanamine by Hofmann bromamide degradation reaction.

(vii) (a) A free expansion means expansion against zero opposing force. Such expansion occurs in a vacuum.

(b) When the gas expands in a vacuum, there is no opposing force, that is . The work done by a system during such expansion is

Thus, no work is done when the gas expands freely in a vacuum.

(viii) Electrode reactions during electrolysis of molten are as follows:

(Oxidation half reaction at anode)

(Reduction half reaction at cathode)

(Overall cell reaction)

Section B

3. (i) Sunscreen lotions contain nanoparticles of zinc oxide and titanium dioxide . These chemicals protect the skin against harmful UV (ultraviolet) rays by absorbing or reflecting the light. Hence sunscreen lotion prevent the skin from damage.
4. Calculate: Electrode reactions are

At anode:

At cathode:

The cell is composed of (anode), Mn(s) Co(s). The cell is represented as:

The standard electrode potential is given by

The standard cell potential is .

5. The process of conversion of a primary aromatic amino compound into a diazonium salt, is known as diazotisation. This process is carries out by adding an aqueous solution of sodium nitrite to a solution of primary aromatic amine (e.g., aniline) in excess of at a temperature below

6. Alkyl halides are polar molecules, therefore, their molecules are held together by dipole-dipole attraction. The molecules of are held together by -bonds. Since the new forces of attraction between water and alkyl halide molecules are weaker than the force of attraction already existing between alkyl halide – alkyl halide molecules and water – water molecules therefore alkyl halides are immiscible (not soluble) in water. Alkyl halide are neither able to form -bonds with water nor are able to break the -bonding network of water.
7. Calculation:

The time required for of reaction to react is .

8. (i) Isotonic solutions: Two or more solutions having the same osmotic pressure are said to be isotonic solutions. e.g. For example, urea solution and sucrose solution are isotonic because their osmotic pressures are equal. Such solutions have the same molar concentrations but different concentrations in If these solutions are separated by a semipermeable membrane, there is no flow of solvent in either direction.

(ii) Hypertonic solution: If two solutions have unequal osmotic pressures, the more concentrated solution with higher osmotic pressure is said to be the hypertonic solution, e.g., For example, if osmotic pressure of sucrose solution is higher than that of urea solution, the sucrose solution is hypertonic to urea solution.

9. (i) X-ray difraction

(ii) Transmission electron microscope Zwitter ion

11. Isomers that involve the exchange of ligands between coordination and ionisation spheres are called ionisation isomers.

e.g. and
12. Ethanenitrile Ethanimine hydrochloride

The reactions involved in the Etard’s reaction are:

(Chromium complex)

(Benzaldehyde)

14. Grignard reagents are highly reactive compounds. They react with water or compounds containing hydrogen attached to the electronegative element. Hence, reactions involving the Grignard reagent must be carried out under anhydrous condition.

49. Section C

15. The reactions involved in the Etard’s reaction are:

For example:

(i)

(ii)

16. Formula:

Calculation: Pressure bar

Now, using formula and rearranging.

concentration in water required for fishes

Now, using formula and rearranging.

The partial pressure of above the water needed for the survival of fish is .

17.

18. (i) This reaction is given by aldehydes having no a-hydrogen atom.

(ii) Aldehydes undergo self-oxidation and reduction reaction on heating with concentrated alkali.

(iii) In Cannizzaro reaction, one molecule of an aldehyde is reduced to alcohol and at the same time the second molecule is oxidised carboxylic acid salt. Thus, the reaction is an example of disproportionation reaction.

For example:

19. (i) Consider moles of an ideal gas enclosed in a cylinder fitted with a frictionless movable rigid piston. It expands isothermally and reversibly from the initial volume to final volume at temperature . The expansion takes place in a number of steps as shown in the figure..

(ii) When the volume of a gas increases by an infinitesimal amount in a single step, the small quantity of work done

(iii) As the expansion is reversible, is greater by a very small quantity up than

Thus, or

Combining equations (1) and (2).

Neglecting the product which is very small, we get

(iv) The total amount of work done during the entire expansion from volume to would be the sum of the infinitesimal contributions of all the steps. The total work is obtained by integration of Equation (3) between the limits of initial and final states. This is the maximum work the expansion being reversible.

Thus,

(v) Using the ideal gas law, ,

(vi) At constant temperature, or Replacing in equation (5) by , we get,

Equations (5) and (6) are expressions for work done in reversible isothermal process.

51. Calculation:

(oxidation at Anode)

(reduction at Cathode)

(overall reaction)

Using formula (i),

Using formula (ii),

The cell potential is given by

The emf of the cell is

21.

(a)

(b)

Toluene chloride Chromium complex

(c)

22. Reverse the Eq. (i)

(i) (s)

Add equations (ii), (iii) and (iv)

(ii) (graphite) .

(iii) (graphite) .

(iv) (s) .

(graphite) .

52. Similarities in Physical Properties:

(i) All block elements are lustrous and shining.

(ii) They are hard and have high density.

(iii) They have high melting and boiling points.

(iv) They are good electrical and thermal conductors.

(v) They have high tensile strength and malleability.

(vi) They can form alloys with transition and nontransition elements.

(vii) Many metals and their compounds are paramagnetic.

(viii) Most of the metals are efficient catalysts.

Similarities in Chemical Properties:

(i) All block elements are eletropositive metals.

(ii) They exhibit variable valencies and form coloured salts and complexes

(iii) They are good reducing agents.

(iv) They form insoluble oxides and hydroxides.

(v) Iron, cobalt, copper, molybadenum, and zinc are biologically important metals.

(vi) They catalyse biological reactions.

53. Differences:

Although most properties exhibited by block elements are similar, the elements of the first row differ from second and third rows in the stabilisation of higher oxidation states in their compounds.

24. (i) The differential rate law for the first-order reaction is:

The equation is of the form . A plot of rate versus is a straight line passing through the origin. The slope of straight line

54. Variation of rate with :

(ii) The integrated rate law is

On rearrangement, the equation becomes

Hence,

The equation is of the straight line. A graph of versus gives a straight line with slope and -axis intercepts as

55. A plot showing log vs time

(iii) Rearranging the integrated rate law equation, we get

The equation has a straight-line form . Hence, the graph of versus is a straight line passing through the origin.

25. Synthetic fibers are artificially prepared by polymerisation of one monomer or copolymerisation of two or more nonomers. e.g., Nylon, terylene etc.

56. Preparation of Terylene:

26. The steps to understand the metal-ligand bonding include are:

(i) Find oxidation state of central metal ion.

(ii) Write valence shell electronic configuration of metal ion.

(iii) See whether the complex is low spin or high spin. (applicable only for octahedral complexes with to electrobnic configurations.)

(iv) From the number of ligands find the number of metal ion orbitals required for bonding.

(v) Identify the orbitals of metal ion available for hybridisation and the type of hybridisation involved.

(vi) Write the electronic configuration after hybridisation.

(vii) Show filling of orbitals after complex formation.

(viii) Determine the number of unpaired electrons and predict magnetic behaviour of the complex.

57. Section D

27. (i) The ionisation enthalpies of transition elements are intermediate between those of s-block or p-block elements. This suggests that transition elements are less electropositive than elements of groups 1 and 2 .

(ii) As the atomic number increases across a transition series, the first ionisation energy increases with some irregularities.

(iii) lonisation enthalpies for a given element increases from the first ionisation enthalpy. to the third ionisation enthalpy, .

(iv) The atoms of elements of the third transition series possess filled -orbitals orbitals show a poor shielding effect on account of their peculiar diffused shape. As a result, the valence electrons experience a greater nuclear attraction. A greater amount of energy is required to ionise elements of the third transition series. The ionisation enthalpies of the elements of the third transition series are therefore much higher than the first and second series.

58. The properties of lanthanoids are:

(i) Soft metals with silvery white colour and moderate densities of . Colour and brightness reduces on exposure to air.

(ii) Good conductors of heat and electricity.

(iii) Except promethium ( ), all are non-radioactive in nature.

(iv) The atomic and ionic raddi decrease from lanthanum (La) to lutetium (Lu). This is known as lanthanoid contraction.

(v) Binding to water is common (i.e.) such that is often found in products when isolated from aqueous solutions.
(vi) Coordination numbers usually are greater than 6 , typically 8,9…(up to 12 found).

(vii) The lanthanoides are strongly paramagnetic. Gadolinium becomes ferromagnetic below (Curie point). The other heavier lathanoids terbium, dysprosium, holmium, erbium, thulium, and ytterbiumbecome ferromognetic at much lower temperatures.

(viii) Magnetic and optical properties are largely independent of environment (similar spectra in gas/ solution/solid).

29. On the basis of charge on complex ion, coordination complex is classified as:

(i) Cationic Complex: A positively charged coordination sphere or a coordination compound having a positively charged coordination sphere is called the cationic complex or cationic sphere complex.

e.g.

(ii) Anionic Complex: A negatively charged coordination sphere or a coordination compound having a negatively charged coordination sphere is called an anionic complex or anionic sphere complex.

e.g.,

(iii) Neutral Sphere Complexes: A coordination complex that does not possess a cationic or anionic sphere are neutral complexes of neutral sphere complexes.

e.g.,

59. Condition of precipitation:

The ionic product (IP) of an electrolyte is defined in the same way as solubility product . The only difference is that the ionic product expression contains a concentration of ions under any condition whereas the expression of contains only equilibrium concentrations. If,

(i) IP = Ksp; the solution is saturated and solubility equilibrium exists.

(ii) IP > Ksp; the solution is supersaturated and hence precipitation of the compound will occur.

(iii) If IP sp; the solution is unsaturated and precipitation will not occur.

31. Preparation of sulphuric acid by contact process: Burning of sulphur or sulphide ores in presence of oxygen to producer .

Catalytic oxidation of with to give in the presence of .

Then made to react with sulphuric acid of suitable normality to obtain a thick oily liquid called oleum.

Then oleum is diluted to obtain sulphuric acid of desired concentration

The sulphuric acid obtained by contact process is 96-98% pure.