2nd PUC Chemistry Model Question Paper 2 with Answers

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Karnataka 2nd PUC Chemistry Model Question Paper 2 with Answers

Time: 3.15 Hours
Max Marks: 70

Part – A

I. Answer all of the following. Each question carries 1 mark. ( 10 × 1 = 10 )

Question 1.
What is the effect of increase in temperature on the solubility of gas in a liquid?
Answer:
Decreases.

Question 2.
Define osmotic pressure.
Answer:
The external pressure applied on the concentrated solution just to stop osmosis is called osmotic pressure.

Question 3.
Mention the concentration of H ions in the solution used In SHE.
Answer:
1 M or 1 molar

Question 4.
From the following plot, predict the order of the reaction.
Answer:

Question 5.

is this reaction an example for Homogeneous or Heterogeneous catalysis.
Answer:
Homogeneous catalysis.

Question 6.
Name the depressant used in separation of ZnS from PbS by froth floatation process.
Answer:
NaCN or Sodium cyanide.

Question 7.
Which noble gas does not occur in nature?
Answer:
Radon or Rn

Question 8.

This reaction is known as
Answer:
Finkelstein reaction.

Question 9.
Give reason: Acetic acid is soluble in water.
Answer:
Due to the formation of hydrogen bond b/w acetic acid molecules and water.

Question 10.
Among the following which is a fat soluble vitamin.
Vitamin-B₁₂, Vitamin – C, Vitamin – D.
Answer:
Vitamin- D

Part – B

II. Answer any FIVE of the following. Each questions carries 2 marks. ( 5 × 2 = 10 )

Question 11.
Give two differences between p-type & n-type semiconductors.
Answer:
P-type:
1. Doped with trivalent atoms (B,Al).
2. Negative charges (electrons) contributes to conduction.

n – type:
1. Doped with pentavalent atoms (P, As, Sb).
2. Holes contributes to conduction.

Question 12.
What is limiting molar conductivity? Represent graphically the variation in molar conductivity with concentration for acetic acid.
Answer:
Molar conductivity of a solution at infinite dilution is called limiting molar conductivity.

Question 13.
Rate constant of a first order reaction is 6.93 × 10^-3 min^-1. Calculate the half – life period.
Answer:

Question 14.
i) What is actinide contraction?
Answer:
The steady decrease in atomic size of the actinides with increase in the atomic number is called actinide contraction.

ii) Which is the common oxidation state exhibited by actinides?
Answer:
+3

Question 15.
How do you prepare diethyl ether by dehydration of ethanol?
Answer:
When ethanol is heated with con. H₂SO₄ at 414K. diethylether is formed

Question 16.
How do you convert benzamide to benzoic acid?
Answer:
When benzamide is heated with dil acid, hydrolysis takes place to form benzoic acid

Question 17.
Give one example each for
i) Tranquilizer
ii) Antiseptic
Answer:
i) Equanil chlordiazepoxide / meprobamate or any other example.
ii) Dettol or chioroxylenol or Tincture of iodine or any other suitable example.

Question 18.
What is saponification with an example.
Answer:
When oil/Fat is heated with aqueous NaOH solution, soap is formed. This reaction is called saponification

Part – C

III. Answer Any FIVE of the following. Each questions carries three marks. ( 5 × 3 = 15 )

Question 19.
How copper is refined by electrolytic method.     (3)
Answer:
In this method a thick rod of impure copper is made as anode and a thin sheet of pure copper is made as cathode. Acidified copper sulphate solution is taken as electrolyte. On passing electricity, copper from the anode goes into the solution and gets deposited on the cathode in the pure state. The impurities are settled at the bottom of the anode as anode mud.
The electrode reactions are as following
At Anode: Cu → Cu²⁺ + 2e^–
At cathode : Cu²⁺ + 2e^– → Cu

Question 20.
i) Write the structure & mention basicity of hypo phosphorous acid.   (2)
Answer:

ii) Which gas is liberated when Zinc reacts with dil HNO₃.     (1)
Answer:
Nitrus Oxide or N₂O

Question 21.
Draw the flow chart for the manufacture of sulphuric acid by Contact process.
Name the catalyst used in the process. (3)
Answer:

Question 22.
i) Give any two reasons for the anomalous behaviour of fluorine. (2)
Answer:

1. Fluorine has smallest size
2. It has highest electro negativity
3. Non availability of d-orbitals
4. High ionisation enthalpy, low F-F bond dissociation enthalpy (Any two)

ii) Give one example of inter halogen compounds.    (1)
Answer:
ClF₃, ICl, BrF₅ or any other suitable example.

Question 23.
i) What are interstitial compounds?    (1)
Answer:
The compounds in which small atoms Like H,C or N are trapped into the crystal Lattices of metals are called interstitial compounds.

ii) Write any two characteristics of interstitial compounds. (2)
Answer:
Characteristics:

1. They have high m.p than the pure metals
2. They are very hard
3. They are chemically inert
4. They retain metallic conductivity (any two)

Question 24.
i) Write the two chemical equations to show the inter conversion of chromates & dichromates in aqueous solution. (2)
Answer:
2CrO₄^2-+2H⁺ → Cr₂O₇^2- + H₂O
Cr₂O₇^2-+ 2OH^– → 2CrO₄^2-+ H₂O

ii) Complete the equation : 5C₂O₄^2-+2MnO₄^–;+ 16H⁺ →                (1)
Answer:
5C₂O₄^2-+2MnO₄^–+ 16H⁺ → 2Mn²⁺ + 8H₂O+ 10CO₂

Question 25.
With the help of valence bond theory account for the geometry & magnetic property of [CO(NH₃)₆]³⁺
Answer:
E.C of CO = 27 = [Al]¹⁸3d⁷4s²
E.C of CO = 24 = [Ar] 3d⁶4s⁰
Orbitais of Co ion =

When strong ligand NH₃ approaches the Co3+ ion pairing of electrons takesplace in 3d orbital occurs against Hund’s rule.

CO³⁺ ion can undergo d²SP³ hybridisation. The six hybrid orbitals overlap with the orbitals of six NH₃ ligands.

(Six pair ofelectron from 6 NH₃ ligands)
Thus the complex has octahedral geometry.
It has no unpaired electrons and hence it is diamagnetic.

Question 26.
i) What is an ambidentate ligand?       (1)
Answer:
The ligands containing more thin one donor atoms but which can ligate through one donor atom are called ambidentate ligands.

(ii)Name the type of structural isomerism that arises in the co-ordination compound compound containing such a ligand.     (1)
Answer:
Linkage isomerism.

iii) Give the IUPAC name of K₂[Zn(OH)₄]
Answer:
Potassium tetrahydroxidozincate (11).

Part – D

Section – I

IV. Answer Any THREE of the following. Each questions carries 5 marks. ( 3 × 5 = 15 )

Question 27.
a) Calculate the packing efficiency in a CCP crystal lattice.     (4)
Answer:
The no of particles per unit cell in fcc structure is 4.
Each atom is considered as one sphere
so the volume of 4 atoms (4 spheres)
= 4 × \(\frac{4}{3}\) πr³ = 16/3 πr³
In a FCC unit cell, the edge length is ‘a’ and radius of the particle is ‘r’ Then
r = \(\frac{\sqrt{2}}{4}\)a
\(\sqrt{2} \mathrm{a}\) = 4r
a= \(\frac{4 r}{\sqrt{2}}\) =2 \(\sqrt{2} \mathrm{r}\)
The volume of the cubic unit cell = a³ = (2 \(\sqrt{2} \mathrm{r}\))³

b) What is the number of particles per unit of a simple cube. (1)
Answer:
one or 1

Question 28.
a) Calculate the osmatic pressure of 0.05% urea solution in water at 20 C.
Given R = 0.0821 Iatm mol^-1K^-1.
Molar mass of urea 60g mol^-1         (3)
Answer:

b) Give two general characteristics of an ideal solution of two liquids. (2)
Answer:

1. Obeys Raoult’s law
2. ∆H of mixing is zero
3. ∆V of mixing is zero
4. Does not forms azeotropic mixtures
5. (A – B) interactions are same as that of (A- A) or (B – B) interactions (Any two)

Question 29.
a) Calculate the emf of the cell in which the following reaction takes place Ni(S) + 2Ag⁺ (0.002M) Ni²⁺ (0.160M) + 2Ag(S), Given that E⁰_cell = 1.05V           (3)
Answer:
A/c to Nernst equation

= 1.05 – 0.02955 log \(\frac{0.16}{(0.002)^{2}}\)
= 1.05 – 0.02955 log 4 × 10⁴
= 1.05 – 0.02955 (log 10000 + log 4)
= 1.05 – 0.02955 (4 + 0.6021)
Ecell = 0.914V

b) A galvanic cell after use is recharged by passing current through it.
What type of cell is it? Give an example.    (2)
Answer:
Secondary cell.
Example: lead storage battery, Nickel – cadmium cell.

Question 30.
a) Rate constant of a reaction at 300K & 400K are 0.034 S^-1 & O.136 S^-1 respectively.
Calculate the activation energy for the reaction [Given : R 8.314JK^-1 mol^-1]
Answer:
WK.T

= 13834Jmol^-1
or 13.8 kj mol^-1

b) Derive the expression for half-life of zero order reaction.    (2)
Answer:
W.K.T rate constant expression Br zero order reaction

Question 31.
a) Mention two applications of adsorption. (2)
Answer:

1. Activated charcoal is used to adsorb colouring matter from the solutions.
2. To control of humidity
3. In gas mask.
4. In chromatographic analysis (Any two)

b) What are emulsions? Give an example for O/W emulsion. (2)
Answer:
Emulsion is a colloidal system in which the dispersed phase is liquid and the dispersion medium are Liquid.
Ex: Milk, Vanishing cream

c) What is the cause for Brownian movement? (1)
Answer:
Brownian movement is due lo the collision of the dispersed phase particles with molecules of the dispersion medium.

Part – D

Section – II

V. Answer Any FOUR of the following. Each questions carries 5 marks. ( 4 × 5 = 20 )

Question 32.
a) Explain SN mechanism with an example.
Answer:
In this mechanism, the nucleophile OH attacks the carbon atom from the side opposite to the bromine atom to form a new C – OH bond. The formation of C – OH bond and cleavage of C- Br bond takes place simultaneously through the transition state in which both OH and Br are partialy bound to the carbon atom.

This is a one step reaction.
Hence this is the rate determining step.
∴rate a [CH₃Br] [OH^–]
∴Hence it is a second order reaction.

b) Name the product formed when chloromethane reacts with
i) aqueous KOH & ii) alcoholic AgCN        (2)
Answer:
i) Methanol or methyl alcohol
ii) Methyl carbylomine or N-methyl carbylamine or methyl isocyanide.

c) Give an example of polyhalogen compound.       (1)
Answer:
CHCl₃. CH₂Cl₂, CCl₄ or Freons or DDT

Question 33.
a) Explain esterification reaction between acetic acid & ethyl alcohol as example.     (2)
Answer:
When acetic acid is heated with ethyl alcohol in the presence of con H₂SO₄ as dehydrating agent ethyl acetate is formed.

b) Boiling point of alcohol is greater than the boiling point of hydrocarbons of comparable molar masses, Why? (1)
Answer:
Due to hydrogen bonding.

c) What is the effect of – NO group on the acidic strength of phenol? Give reason. (2)
Answer:
NO₂ group increases the acidic strength ofphenol since -NO₂ group is electron with drawing group or due to – I effect.

Question 34.
a) Explain Etard reaction.    (2)
Answer:
When toluene is treated with CrO₂Cl₂ and CS₂ followed by hydrolysis benzaldehyde is formed.

b) Name the products A&B in the following reaction.     (2)
Answer:
A = Aldol or 3 – hydroxybutanal
B = Chrotonaldehyde or But – 2 – enal

c) Name the reagent used in the decarboxyaltion of carboxylic acid.      (1)
Answer:
C = Sodalime (NaOH + CaO)

Question 35.
a) How do you convert benzene diazonium chloride into chlorobenzene. Name the reaction.      (3)
Answer:
When benzene diazonium chloride reacts with cuproces chloride in HCl, chlorobenzene is formed.

OR
When benzene diazonium chloride reacts with copper in the presence of HCl chlorobenzene is formed.

b) Explain Hoffmann Bromamide reaction with an example.     (2)
Answer:
When amide reacts with bromine in the presence of aqueous /alcoholic NaOH, primary amine is formed. This reaction is called Hoffmann’s bromamide reaction.
R – CONH₂ + Br₂ + 4NaOH → R-NH₂ + Na₂ CO₃ + 2NaBr + 2H₂O
Ex: CH₃CONH₂ + Br₂ + 4NaOH → CH₃NH₂ + Na₂CO₃ + 2NaBr + 2H₂O

Question 36.
a) Write the Haworth structure of maltose.    (2)
Answer:

b) What are hormones? Give one biological function of insulin.     (2)
Answer:
Hormones are the biochemical messengers secreted by endocrine (ductless) glands.
Insulin regulates the blood sugar level.

c) What are nucleosides?      (1)
Answer:
The compounds containing pentose sugar and nitrogen base are called nucleosides.

Question 37.
a) Name the manomers of nylon – 6,6.     (2)
Answer:
Hexamethylene diamine and adipic acid.

b) How is Neoprene prepared? Give equation.      (2)
Answer:
Neoprene is formed by the addition polymerisation of chloroprene in the presence of peroxide catalyst.

c) Give an example for thermoplastic polymer.     (1)
Answer:
PVC or polyethylene or polystyrene (any one)

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