HSC SAMPLE PAPER-5 Chemistry

HSC SAMPLE PAPER-5 Chemistry

83. Section A

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

(i) Two solutions have the ratio of their concentrations 0.4 and ratio of their conductivities 0.216 . The ratio of their molar conductivities will be:
(a) 0.54
(b) 11,574
(c) 0.0864
(d) 1.852

(ii) In Frenkel defect:

(a) Electrical neutrality of the substance is changed

(b) Density of the substance is changed

(d) Overall electrical neutrality is preserved.

(iii) Teflon is chemically inert, due to presence of….
(a)

bond
(b) C-Fbond
(c) -bond
(d) bond

(iv) For the cell, (s), if concentration of an ion in the anode compartment is increased by a factor of 10, The emf of the cell will:

(a) Increase by

(b) Increase by

(d) Decrease by

(v) In which year the Bronsted Lowry concept was given?
(a) 1922
(b) 1923
(c) 1925
(d) 1927

(vi) acid when heated with conc. forms:
(a)
(b)
(c)
(d)

(vii) The conjugate base of is:
(a)
(c)
(b)
(d)

(viii) Identify the correct statement:

(a) Vapour pressure of solution is higher than that of pure solvent

(b) Boiling point of solvent is lower than that of solution

(d) Osmosis is acolligative property.

(ix) The boiling point of the ethers with the increase in the number of the carbon atoms in the ethers.
(a) Increases
(b) Decreases
(c) Remains the same
(d) None of them

(x) Which of the following compounds contains azo linkage?

(a) Hydrazine

(b) p-Hydroxyazobenzene

(d) Ethylenediamine

85. Answer the following questions:

(i) What type of inter molecular force leads to high density polymer?

(ii) Mention two applications of coordination compounds.

(iii) Write two properties of a buffer solution.

(iv) Write the names of allotropic forms of selenium.

(v) Calculate the maximum work when of are expanded isothermally and reversibly from the pressure of 1.6 bar to 1 bar at .

(vi) The atomic number of an element is 90 . Is this element Diamagnetic or paramagnetic?

(vii) Define sustainable development.

(viii) Which of the three types of packing used by metals makes the most efficient use of space and which makes the least efficient use?

86. Section B

87. Attempt any Eight of the following questions:

What are synthetic resins? Name some natural and synthetic resins.
The of rain water collected in a certain region of Maharashtra on particular day was 5.1 calculate the concentration of the rain water and its percent. Dissociation.
Give the reagents and conditions necessary to prepare phenol from chlorobenzene.
A reaction occurs in the following steps:

(i) (slow)

(ii) (fast)

(a) Write the equation of overall reaction.

(b) Write down rate law.

Give the reaction mechanism.
The normal boiling point of ethyl acetate is . A solution of of a non-volatile solute in of ethyl acetate boils at . Evaluate the molar mass of solute if for ethyl acetate is .
A carbonyl compound ‘ ‘ having molecular formula forms crystalline precipitate with sodium bisulphite and give positive iodoform test but does not redues Fehling’s solution. Write the structure of carbonyl compound.
Aqueous solution of sodium carbonate is alkaline whereas aqueous solution of ammonium chloride is acidic. Explain.
Give the Nitration and sulphonation reactions of Chlorobenzene.
The first ionisation enthalpies of and are 1000 , 1256 and respectively. Explain the observed trend.
Consider the cell notation

Write cell reaction of cell.

Name the factors governing the equilibrium constants of the coordination compounds.

88. Section C

89. Attempt any Eight of the following questions:

is tetrahedral complex. Draw its box orbital diagram. State which orbitals participate in hybridisation.
(i) Equilibrium constant of the reaction,

is . What is the standard potential of the cell in which the reaction takes place?

(ii) Write a short note on the Gibbs energy.

How will you illustrate the principle, minimisation of steps?
Explain reverse osmosis.
An ether (A), , when heated with excess of hot produce two Alkyl halides which on hydrolysis form compound (B) and (C), oxidation of (B) gave and acid (D). where as oxidation of (C) gave a ketone (E). Deduce the structural formula of (A), (B), (C). (D) and (E).
(i) Calculate molar conductivities at zero concentration for and .

Given: molar ionic conductivities of and ions are respectively. 104, 76.4, 50.1 and 159.6 . (ii) The molar conductivity of acetic acid at is . Calculate its degree of dissociation in solution and dissociation constant if molar conductivity of acetic acid at zero concentration is .

(i) What is the action of hydrazine on cyclopentanone in presence of in ethylene glycol?

(ii) Give the cross aldol condensation reaction.

(iii) How you will convert Acyl chloride to acid amide.

Calculate the packing efficiency of metal crystal that has simple cublic structure.
Explain Gabriel phthalimide synthesis.
(i) Convert propene to 1-nitropropane.

(ii) Arrange the following compounds in order of increasing boiling points: bromoform, chloromethane, dibromomethane, bromomethane.

(iii) How will you convert 2-bromobutane to but-2-ene?

Arrange the following carboxylic acids with increasing order of their acidic strength and justify your answer.

(iii)

Explain the trends in atomic radii of block elements.

90. Section D

91. Attempt any Three of the following questions:

(i) Draw neat diagram of dCMP.

(ii) Give the structure of Adenine.

(iii) Give the structure of Guanine.

(iv) Give the structure of Thymine

(i) The rate constant for the first order reaction is given by . Calculate activation energy of the reaction. (ii) A first order gas phase reaction has activation energy of . If the pre-exponential factor is . What is the rate constant of the reaction at ?
Write similarities and differences between lanthanides and actinoids.
Derive the expression for PV work.
Give four user of Neon and Orgon.

92. Answer Key

93. Section A

(i) (a) 0.54

(ii) (d) Overall electrical neutrality is preserved

(iii) (b) C-Fbond

(iv) (b) Increase by

(v) (b) 1923

(vi) (c)

(vii)

(c)

(viii) (b) Boiling point of solvent is lower than that of solution

(ix) (a) Increases

(x) (b) p-Hydroxyazobenzene

(i) Van der Walls forces between closely packed linear polymeric chains are responsible for high-density polythene.

(ii) (a) In Biology: Several biologically important natural compounds are meta complexes. They play important role in a number of processes occurring in plants and animals. For example, chlorophyll present in plants is a complex of . Haemoglobin present in the blood is a complex of iron.

(b) In Medicines:

Pt complex, cisplatin is used in the treatment of cancer.
EDTA is used for the treatment of lead poisoning.

(c) To Estimate the Hardness of Water: Hardness of water is due to the presence of and ions. The ligand EDTA forms stable complexes with and . It can, therefore, be used to estimate hardness.

(iii) Properties of Buffer Solution:

(a) When a small amount of strong acid (or strong base) is added to a buffer solution, there is no significant change in the value of . The of a buffer solution is independent of the volume of the solution. Hence, the dilution of a buffer solution will not change its .

(b) The of a buffer solution does not change even if it is kept for a long time.

(iv) Allotropes of selenium are red and grey selenium.

(v) Number of moles of

Gas constant

Now, using formula,

The maximum work done is .

(vi) The electronic configuration of element with atomic number is . There are two unpaired electrons in the orbital of the element Hence, it is paramagnetic.

(vii) Sustainable development is the development that meets the needs of the present without compromising the ability of future generations to meet their own need.

(viii) Out of the three types of packing face-centered cubic (or ccp or hcp) lattice makes the most efficient use of space while simple cubic lattice makes the least efficient use of space.

94. Section B

(i) Synthetic resins: These polymers are artificially prepared by polymerisation of one monomer or copolymerisation of two or more monomers e.g. nylon and terylene.

Synthetic polymers are further divided into three subtypes: fibres, synthetic rubbers, and plastics.

(a) Natural resins: Natural rubber, silk, wool etc.

(b) Synthetic resins: Nylon, terylene, neoprene, etc.

Considering that the of rainwater is due to the dissociation of a monobasic strong acid ( , we have

From formula (ii),

Percent dissociation

(i) ion concentration is

(ii) Percent dissociation is .

Reagents and conditions required to prepare phenol from Chlorobenzene are:

Reagents: , dil .

Conditions: Temperature and Pressure

(i) The addition of two steps gives the overall reaction as

(ii) Step (i) is low. The rate law of the reaction is predicted from its stoichiometry. Thus,

(iii) is produced in step (i) and consumed in step (ii) or F is reaction intermediate.

95. Step 1:

96. Step 2:

Mass of solute

mass of solvent

Molar mass of solute

‘A’ is
Or

(i) Sodium carbonate is a salt of weak acid and strong base . When dissolved in water, it dissociates completely.

(ii) The ions of salt have no tendency to react with ions of water since the possible product of the reaction is a strong electrolyte.

(iii) On the other hand, the reaction of ions of salt with the ions from water produces unionized .

Thus, the hydrolytic equilibrium for is,

(iv) As a result of excess ions produced, the resulting solution of is alkaline.

(v) Similarly, ammonium chloride is salt of strong acid and weak base . When is dissolved in water, it dissociates completely as,

(vi) ions of salt have no tendency to react with water because the possible product is a strong electrolyte.

(vii) The reaction of ions with ions form unionised . The hydrolytic equilibrium for is then written as

(viii) Due to the presence of an excess of ions, the resulting is acidic.

(i) Nitrotion: It is carried out by heating haloarene with conc. in presence of conc. .

(ii) Sulphonation: It is carried out by heating haloarence with Fuming .

(i) The elements , and belong to third period of the periodic table.

(ii) Across a period, effective nuclear charge increases and atomic size decreases with increase in atomic number. Therefore, the energy required for the removal of an electron from the valence shell (i.e.) increases in the order: .

(i) At anode (oxidation half reaction)

(ii) At cathode (Reduction half reaction)

Overall net reaction

(i) and (ii) for balancing electron

The stability of a complex or equilibrium constant is governed by:

(i) Charge to size ratio of the metal ion.

(ii) Nature of the ligand.

97. Section C

(i) Box orbital diagram of

(ii) One and three orbitals participate in hybridization.

(i) Calculate:

For the given reaction, .

Using formula,

The standard cell potential of cell is .

(ii) Gibbs Energy: As pointed out in the preceding section, it is necessary to determine, and for predicting the spontaneity of a reaction. We are more interested in the system (reaction mixture). It is, therefore convenient to consider the criterion of spontaneity in terms of the thermodynamic properties of a system. This problem was solved by American theoretician J.W. Gibbs. He introduced a new thermodynamic property called Gibbs energy usually denoted by .

The Gibbs energy is defined as

Where is enthalpy and entropy of the system. Since H, T and S are state functions, G is state function. A change in Gibbs energy depends on initial and final states of the system and not on a path connecting the two states.
The change in Gibbs energy at constant temperature and constant temperature and constant pressure is given by

98. Reduce derivatives (Minimization of steps):

In organic synthesis protecting or blocking groups is commonly used. According to this principle of green chemistry, unnecessary derivatisation, for example, installation or removal of the use of protecting groups should be minimised or avoided if possible because such steps require additional reagents and can generate waste.

99. Illustration:

(i) In organic synthesis, the protection of some functional groups is required. Again, the deprotection of the functional group is required at the end. For example: Synthesis of -hydroxybenzoic acid from -hydroxybenzaldehyde.

(ii) In such cases, the atom economy is also less.

(iii) The green chemistry principle aims to develop the methodology where unnecessary steps should be avoided. This can be done if possible by using practicable biocatalytic reactions which very often need no protection of the selective group.

When two solutions of unequal concentrations are separated by a semipermeable membrane which selectively does not permit the passage of dissolved solute particles, i.e., molecules, ions etc flow of solvent takes place from dilute to concentrated sides due to osmosis. If a hydrostatic pressure in excess of osmotic pressure is applied on the concentrated side to dilute side across the membrane.

Reverse Osmosis Cell

This process is called as reverse osmosis method pure solvent is separated from its contaminates, rather than removing contaminants from the water.

(i) The ether (A) with molecular formula is

(ii) Reacts with hot to produce two alkyl halides as follows:

(iv) Oxidation of (C) gives ketone

Hence, structural formulae of compounds to are

(A)

(2-Ethoxypropane)

(B) (Ethanol)

(c)

(D) (Ethanoic acid)

(E)

(Propanone)

(i) According to Kohrausch law,

(a)

(b)

(ii) The degree of dissociation,

(ii)

(iii)

Relationship between edge and radius for .

Volume of sphere

Number of particles in simple cubic

Volume of one particle

Packing efficiency

Packing efficiency of scc

(i) Formation of the potassium salt of phthalimide from phthalimide on reaction with alcoholic potassium hydroxide.

Potassium salt of
Phthalimide

(ii) Formation of -alkyl phthalimide from the potassium salt by reaction with an alkyl halide.

(iii) Alkaline hydrolysis of -alkyl phthalimide to form the corresponding primary amine.

1-Bromopropane

Silver nitrite

1-Nitropropane (ii) The comparative boiling points of halogen derivatives are mainly related with van der waals forces of attraction which depend upon the molecular size. In the present case all the compounds contain only one carbon. Thus the molecular size depends upon the size of halogen and number of halogen atoms present.

Thus increasing order of boiling point is,

(iii)

(i) Increasing order of their acidic strength: (2) > (3) > (1)

(ii) Oxygen atom is electronegative and exerts electron withdrawing inductive effect ( -1 effect).

(iii) Thus, compound (2) and (3 are more acidic as compared to (1).

(iv) However, the inductive effect decreases as the oxygen in the ring moves away from the carboyxl group. Therefore, compound (3) is less acidic than compound (2).

(i) Atomic radii of the elements of the transition series decrease gradually from left to right.

(ii) As we move across a transition series from left to right, the nuclear change increases by one unit at a time.

(iii) The last filled electron enters a penultimate ( 1) subshell. However, orbitals in an atom are less penetrating or more diffused and, therefore electrons offer smaller screening effects.

(iv) The result is that effective nuclear charge also increases as the atomic number increases along with a transition series. Hence, the atomic radii gradually decrease across a transition series from left to right.

Trends in atomic radii of block elements.

100. Section D

27.

(i)

(ii)

(iii)

G (iv)

(i) The given rate constant equation is

Arrhenius equation is

Comparing (1) and (2),

4. The electronegativityof all the elements inboth the series is lowand are said to behighly reactive.	Lanthanoids do not formsoxocations, but actinidesform oxocations such as
5. The nitrates,perchlorates andsulphates of allthe elements aresoluble while thehydroxides fluoridesare carbonates areinsoluble.	Most of the lanthanoidare colourless in naturewhere as the actioniodsare coloured ions.

The energy of activation of the reaction is .

(ii) Arrhenius equation

(i)
(i) Consider a certain amount of gas at constant pressure is enclosed in a cylinder fitted with a frictionless, rigid movable piston of area . Let the volume of the gas be at temperature . This is shown in the adjacent diagram.

(ii) On expansion, the force exerted by a gas is equal to area of the piston multipled by pressure with which the gas pushes against piston. This pressure is equal. in magnitude and opposite in sign to the external atmospheric pressure that opposes the movement and has its value