HSC SAMPLE PAPER-4 Chemistry

HSC SAMPLE PAPER-4 Chemistry

Section A

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

(i) In crystal lattice formed by bcc unit cell the void volume is
(a)

(b)
(c) 32
(d)

(ii) The number of carbon atoms present in the ring of -caprolactam is
(a) Five
(b) Two
(c) Seven
(d) Six

(iii) Which of the following element does not show oxidation state of +4 ?
(a) 0
(b)
(c)
(d)

(iv) Bond enthalpies of and bonds are and . respectively. Enthalpy of formation of is:
(a)
(b)
(c)
(d)

(v) Which of the following is the least acidic compound? (a)

(c)

(b)

(d)

(vi) The colligative property of a solution is
(a) vapour pressure
(b) boiling point
(c) osmotic pressure
(d) freezing point

(vii) The molecule of glucose is also called:
(a) Glucopyranose
(b) Pyranose
(c) Rabinose
(d) None of them

(viii) reacts with water to form
(a)
(c)
(b)
(d)

(ix) For the hydronium ion concentration would be
(a)
(b)
(c)
(d)

(x) On diluting the solution of an electrolyte

(a) both and increase

(b) both and decrease

(c) increase and decreases

(d) decrese and increases

Answer the following questions:

(i) Under what conditions the cell potential is called standard cell potential?

(ii) Give names of the purines.

(iii) The of a solution is 6.06. Calculate its ion concentration.

(iv) What is the action of bromine on magnesium metal?

(v) Write the relationship between rate constant and half-life of first order and zeroth order reaction.

(vi) Mention two properties that are common to both hcp and ccp lattices.

(vii) Write the order of basicity of aliphatic alkylamine in gaseous phase.

(viii) Write name of the electrophile used in kolbe’s reaction.

64. Section B

65. Attempt any Eight of the following questions:

3. Why -amino acids have high melting points compared to the corresponding amines or carboxylic acids of comparable molecular mass?
4. In solution is . Calculate the of solution.
5. Alkyl halides are generally not prepared by free radical halogenation of alkanes..
6. Write reaction showing conversion of benzonitrile into benzoic acid.
7. What is Henry’s law?
8. Write structural formulae for

a. Pentane-1,4-Diol b. Cyclohex-2-en-1-ol

9. What are acids and bases according to Arrhenius theory?
10. Write four points of difference between properties of phenol and ethyl alcohol.
11. Write IUPAC names of following compounds.

12. Write the reaction of conc. with sugar. What is the role of in this reaction.
13. Write Nerst equation. What part of it represents the correction factor for non-standard state conditions?
14. Distinguish between order and molecularity of a reaction.

Section C

67. Attempt any Eight of the following questions:

15. Write preparation, properties and uses of Teflon.
16. An element has bcc structure with unit cell edge length of 288 pm. How many unit cells and number of atoms are present in of the element?
17. Write a note on Stephen reaction.
18. Draw geometric isomers of:

(a)

(b) Enantiomers of

(c) Geometrical isomers of

19. What is meant by diamagnetic and paramagnetic? Give one example of diamagnetic and paramagnetic transition metal and lanthanoid metal.
20. (i) A solution ot citric acid in of acetic acid has a boiling point elevation of . If for acetic acid is . What is the molality of solution?

(ii) An aqueous solution containing of non- volatile compound in of water freezes at . Determine molar mass of solute.

[ for water . of water ]

21. Complete the following reaction sequences by writing the structural formulae of the organic compounds ‘ ‘, ‘ ‘ and ‘C’.

22. Obtain the relatioship between and for gas phase reactions.
23. Distinguish between ethylamine, diethylamine and triethylamine by using Hinsberg’s reagent?
24. How will you represent first order reactions graphically?
25. (i) Write reaction showing aldol condensation of cyclohexanone.

(ii) How acetone is converted into propane.

(iii) How propanal is converted into propane.

26. Explain the construction and working of standard hydrogen electrod.

68. Section D

69. Attempt any Three of the following questions:

27. Explain atom economy with suitable example.
28. Calculate at for the reaction,

How much PV work is done?

29. Cerium and Terbium behaves as good oxidising agents in +4 oxidation state. Explain.
30. Draw isomers of the following (i) (ii) . (iv) .
31. Explain the trend in following atomic properties of group 16 elements.

(i) Atomic radii

(ii) Ionisation enthalpy

(iii) Density

(iv) Electronegativity.

[A] Answer Key

71. Section A

1. (i) (c)

(ii) (d) Six

(iii) (a)

(iv) (b)

(v) (b)

(vi) (c) osmotic pressure

(vii) (a) Glucopyranose

(viii) (d)

(ix) (b)

(x) (c) increases and decreases

2. (i) The cell potential measured under the standard conditions is called standard cell potential. The standard condition chosen are concentration of a solution. pressure for gases solids and liquids in pure form and (ii) Adenine and Guanine

(iii) The ion concentration of the solution is .

(iv) Bromine reacts with magnesium to form magnesium bromide:

(v) (i) For first order reaction,

(ii) For zero order reaction,

(vi) Properties common to both hcp and ccp lattice are the same coordination number of the particles (i.e., 12 ) and the same packing efficiency .

(vii) Order of basicity of aliphatic alkylamine in gaseous phase: amines amines amine.

(viii) Carbon dioxide

72. Section B

3. (i) This is due to the peculiar structure called zwitter ion structure of -amino acids.

(ii) -Amino acid molecule contains both acidic carboxyl group as well as basic amino group.

(iii) Proton transfer from the acidic group to the basic group of amino acid forms a salt, which is a dipolar ion called zwitter ion.

Thus, -amino acids have high melting points compared to the corresponding amines or carboxylic acids of comparable molecular mass.

4. From formula (i),

From formula (ii),

of the solution is 10.4579 .

5. Free radical halogenation of alkanes leads to the formation of a mixture of mono and poly halogen compounds. Hence, free radical halogenation of alkanes is not suitable for the preparation of alkyl halides.
6. dil.

Benzonitrile

7. It states that the solubility of a gas in a liquid is directly proportional to the pressure of the gas over the solution. Thus,

Where, is the solubility of the gas in is the pressure of the gas in bar over the solution. , the proportionality constant is called Henry’s law constant.

8. (i)

Pentane-1,4-diol

(ii)

Cylohex-2-en-1-oL

9. According to Arrhenius theory, acids and bases are defined as follows:

(i) Acid: An acid is a substance that contains hydrogen and gives ions in an aqueous solution. e.g.,

(ii) Base: base is a substance that contains the group and produces hydroxide ions ions) in aqueous solution

e.g.,

10.

11. (i) 1-Chloro-4-ethylcyclohexane

(ii) 1,4-Dichloro-2-methylbenzene

The reaction is:

acts as the catalyst in the reaction and helps to remove the water from the sugar molecule.

13. (i) For any general reaction, :

Nernst equation is given by

Where moles of electrons used in the reaction, Faraday

temperature in kelvin,

gas constant
(ii) The seond term in the Nernst equation is the correction for non-standard state conditions.

Correction factor is

14.

73. Section C

74. Preparation of Teflon:

(i) The monomer used in preparation of teflon is tetrafluoroethylene. , which is a gas at room temperature.

(ii) Tetrafluoroethylene is polymerised by using freeradical initiators such as hydrogen peroxide or ammonium persulphate at high pressure to produce polytetrafluoroethylene (teflon).

Properties of Teflon:

(i) Teflon is tough chemically inert and resistant to heat and attack by corrosive reagents.

(ii) C-F bond is very difficult to break and remains unaffected by corrosive alkali, organic solvents.

Uses: Teflon is used in making non-stick cookware, oil seals, gaskets, etc.

16. (i) For bcc unit cell, .

Using formula (i).

Number of atoms in of element.

(ii) Using formula (ii),

Number of unit cells in element

cis isomer

trans isomer

Number of atoms in element is

Number of unit cells in element is

17. Nitriles are reduced to imine hydrochloride by stannous chloride in presence of hydrochloric acid which on acid hydrolysis give corresponding aldehydes. This reaction is called stephen reaction.

Alkone nitrile

Imine hydrochloride

e.g.,

Ethanal

18. (i) Geometric isomers of .

(ii) Enantiomers of .

(iii) Geometrical isomers of

19. The substances with all electrons paired are weakly repelled by magnetic fields. Such substances are called diamagnetic substances.

75. Examples:

20. (i) Given: Boiling point elevation of acetic acid

Mass of acetic acid

To find: Molality of the solution

76. Formula:

Calculation: Using formula and rearranging, we get,

The molality of the solution is .
(ii) Mass of stolute

molar mass of solute ?

or

21.

(A) (Major)

2, 3-Dibromobutane (B)

22. (i) At constant pressure, and are related as

(ii) For reactions involving gases, cannot be neglected. Therefore,

where, is the volume of gas-phase reactants and that of the gaseous products.

(iii) We assume reactant and product behave ideally. Applying an ideal gas equation, . Suppose that moles of gasseous reactants produce moles of gaseous products, Then,

(iv) Substitution of equation (3) into equation (2) yields

where, is the difference between the number of moles of products and those of reactants.

23. (i) Ethylamine (Primary amine) reacts with benzenesulphonyl chloride to form -ethyl benzenesulphonyl amide.

The hydrogen attached to nitrogen in -ethylbenzene sulphonamide is strongly acidic. Hence it is soluble in alkali.

(ii) Diethylamine reacts with benzene-sulphonyl chloride to give -diethyl benzene sulphonamide.

– diethylbenzenesulphonamide does not contain any -atom attached to the nitrogen atom. Hence it is not acidic and does not dissolve alkali.

(iii) Triethylamine does not react with benzenesulphonyl chloride (i.e., Hinsberg’s reagent) as it does not contain any -atom attached to the nitrogen atom.

24. (i)

Variatioin of rate with

(ii) From

or

hence

Fig.
(iii)

25. (i)

-unsaturated ketone

(ii)

(iii)

26. Construction: It consists of a platinum plate, coated with platinum black used as electrode. This plate is connected to the external circuit through sealed glass tube containing mercury.

The platinum electrode is immersed in ion solution. The solution is kept saturatted with dissolved by bubbling. Hydrogen gas under pressure through the side tube of the jacket.

Working: gas of is passed through an inlet provided near the top. It gets absorbed on the colloidal platinum and equilibrium exists between adsorbed gases and from the solution.

Electrode Reaction:

of oxidation or reduction taken to be zero.

Electode Representation:

Variatioin of rate with

(ii) From

or

hence

Fig.
(iii)

26. (i)

-unsaturated ketone

(ii)

(iii)

27. Construction: It consists of a platinum plate, coated with platinum black used as electrode. This plate is connected to the external circuit through sealed glass tube containing mercury.

The platinum electrode is immersed in ion solution. The solution is kept saturatted with dissolved by bubbling. Hydrogen gas under pressure through the side tube of the jacket.

Working: gas of is passed through an inlet provided near the top. It gets absorbed on the colloidal platinum and equilibrium exists between adsorbed gases and from the solution.

Electrode Reaction:

of oxidation or reduction taken to be zero.

Electode Representation:

29. (i) Cerium ( ) and Terbium ( show +4 oxidation states. Their electronic configurations are given below:

(ii) It is clear from the configuration of that is favoured by its noble gas configuration. But it can be easily converted into stable by a gain of an electron. Due to this reason, is a good oxidising agent.

30. (i) Cis and trans isomers of

(ii) Cis and trans isomers of

(iii) Cis and trans isomers of

cis isomer

31. (i) Trends in 16-Group

(a) Atomic radii and ionic radii.
Down the group atomic radii increases due to the increase in the number of shells since the number of electrons also increases.

(b) Density

Down the group density increases because the atomic radius increases due to the increase in the volume of atoms, thus the density also increases.

80. (c) lonisation enthalpy

The lst ionization enthalpies of the elements of group 16 are unexpectedly lower, while their Ilnd ionisation enthalpies are higher than those of the correspending elements of group 15. Due to the addition of the valence shell.

(d) Electronegativity

The elements of group 16 have higher value of electronegativity then the corresponding elements of group 15.