2nd PUC Chemistry Model Question Paper 1 with Answers

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Karnataka 2nd PUC Chemistry Model Question Paper 1 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 are isotonic solutions?
Answer:
Solutions having same osmotic pressure at a given temperature are called isotonic solutions.

Question 2.
What is the van’t Hoff factor for potassium sulphate in very dilute aqueous solution?
Answer:
3

Question 3.
Write the equation for the reaction occurring at the anode in the lead acid battery when it is in use.
Answer:
Pb + SO₄^2-→ PbSO₄ + 2e^–

Question 4.
What is collision frequency?
Answer:
The number of collisions per second per unit volume of the reaction mixture is called collision frequency.

Question 5.
State Hardy – schulze rule.
Answer:
It states that “Higher the valency of the active ion, more will be its precipitating power”.

Question 6.
Which type of ore is concentrated by froth floatation?
Answer:
Sulphide ores.

Question 7.
Noble gases have very low boiling point. Why?
Answer:
Due to weak dispersion forces b/w their atoms.

Question 8.
Give the IUPAC name of CH₂ = CHCl.
Answer:
Chloro Ethene

Question 9.
What is the oxidizing agent used in Etard’s reaction?
Answer:
Chromyl chloride or CrO₂Cl₂

Question 10.
Give an example for α -amino acid which is basic.
Answer:
Lysine (any other)

Part – B

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

Question 11.
How many tetrahedral and octahedral voids are possible if the number of close packed spheres in two layers is N?
Answer:
2N → Tetrahedral voids
N → Octahedral voids

Question 12.
Calculate the mass of aluminium deposited at cathode when 193 C of current is passed through molten electrolyte containing dissolved alumina. Given molar mass of A = 27 g mol^-1, 1F = 96500 Cmol^-1
Answer:
3 x 96500 C Can deposit 27 grams of Al 193 C = ?
= \(\frac{193 \times 27}{96500 \times 3}\) = 0.018 g of Al

Question 13.
Write Arrhenius equation. What is E_a in the equation called?
Answer:
K = \(A \cdot e^{\frac{-E a}{R T}}[latex]
Where Ea = Energy of activation

Question 14.
Give reasons:
i) Element cerium (Ce) exhibits + 4 oxidation state.
Answer:
It has noble gas configuration in +4 oxidation state.

ii) Actinoid contraction is greater from element to element than lanthanoid contraction.
Answer:
Due to poor shielding by 5f electrons.

Question 15.
How do you convert propene into propan – 2 – ol?
Answer:
Propene reacts with water in the presence of acid catalyst (dil. H₂SO₄) to form propan – 2 – ol

Question 16.

Answer:

Question 17.
What are analgesics? Give an example.
Answer:
These are drugs that reduce pain.
Ex: aspirin or morphine

Question 18.
What are anti-fertility drugs? Give an example.
Answer:
These are drugs used to control the population or birth control drugs.
Ex: norethindrone or novestrol

Part -C

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

Question 19.
Explain with equations Van-Arkel method of refining of Zirconiur. (3)
Answer:
Zirconium is refined by Van-Arkel method.
The crude metal is heated in an evacuated vessel with iodine. The metal sodide being more covalent volatizes.
Zr + 2I₂ → ZrI₄
The metal iodide is decomposed on a tungsten filament, electrically leated to about 1800K. The pure metal is thus deposited on the filament
ZrI₄ → Zr + 2I₂

Question 20.
Describe with equations the manufacture of nitric acid by Ostwal’s process. (3)
Answer:
This method is based upon the catalytic oxidation of NH₃ by atmospheric oxygen.

Nitric oxide thus formed combines with oxygen giving NO₂
2NO_(g) +O_2(g) → 2NO_2(g)
Nitrogen dioxide so formed, dissolves in water to give HNO₃
3NO_2(g) + H₂O_l → 2HNO_3(aq) + NO_(g)
NO thus formed is recycled and the aqueous HNO₃ can be concentrated by distillation.

Question 21.
Mention three anomalous behaviour of oxygen. (3)
Answer:

1. Oxygen is diatomic gas which other elements of this group are solids.
2. Oxygen forms hydrogen bounds while other elements do not.
3. Oxygen has a maximum co valency of four while other elements can show a maximum of six.

Question 22.
a) Complete the following equation:
6NaOH + 3Cl₂ → ______ + ______ + 3H₂O
Hot & concentrated
Answer:
6NaOH + 3Cl₂ → 5NaCl + NaClO₃
(Hot & conc)

b) Inter halogen compounds are more reactive than halogens. Why?   (2 + 1)
Answer:
The bond b/w atoms in inter halogens (x – x¹) is weaker than the bond in halogens (x – x).

Question 23.
a) Transition metals and their compounds are used as catalysts. Give two reasons.
Answer:

• They exhibit variable oxidation states.
• They have more surface area
• They can form complexes

b) Write the outer electronic configuration of chromium (atomic no = 24)     (2 + 1)
Answer:
3d⁵4S¹

Question 24.
How is potassium permanganate prepared? Give equations. (3)
Answer:
Potassium permanganate is prepared by the fusion of MnO₂ with an alkali metal hydroxide and an oxidising agent like KNO₃. This produces the dark green K₂MnO₄ which disproportionates in a neutral.
OR
acidic solution to give permangenate
2MnO₂ + 4KOH + O₂ → 2K₂MnO₄ + 2H₂O
3MnO₄^2-+ 4H⁺ → 2MnO4^– + MnO₂ + 2H₂O

Question 25.
a) Mention any two applications of co-ordination compounds?
Answer:

1. Coordination compounds are used as catalysts for many industrial processes.
2. The pigment responsible for photo synthesis chlorophyll is a co-ordination compound of Mg.

b) What is crystal field splitting?   (3)
Answer:
The splitting of degenerate levels of the central metal atom / ion under the influence of legands approaching it is definite geometry is called crystal field splitting.

Question 26.
For [Co(en)₃]Cl₃ :      (3)
i) Give the IUPAC name,
Answer:
tris (ethane 1,2 – diamine) cobalt (111) chloride.

ii) Give the co-ordination number of the central metal ion,
Answer:
6

iii) What type of stereo-isomerism does it exhibit?
Answer:
Optical isomerism.

PART – D

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

Question 27.
a) Calculate the number of atoms per unit cell of FCC.
Answer:
No.of atoms per unit cell of FCC = 8 comer atoms × [latex]\frac{1}{8}\) atom +6 face centred atoms × \(\frac{1}{2}\)
i.e., 8 × \(\frac{1}{8}\) + 6 × \(\frac{1}{2}\) = 1 + 3 = 4

b) What is ferro magnetism? Give an example for ferromagnetic substance.
Answer:
The substances which are strongly affected by magnetic field are called ferromagnetic substances and the phenomenon is known as ferro magnetism.
Ex: Iron or Nickel, or Cobalt or CrO₂ any other

c) Give an example for molecular solid.    (2 + 2 + 1 )
Answer:
I₂ or any other suitable example.

Question 28.
a) The vapour pressure of pure benzene at a certain temperature is
0. 850 bar. When 0.5g of a non-volatile solute is added to 39.0 g of benzene [molar mass of benzene 78g mol^-1], vapour pressure of the solution is 0.845 bar. What is the molar mass of a non – volatile solute?
Answer:
W.K.T

b) State Raoult’s law for a solution of 2 volatile liquids. Give an example for liquid mixture that shows negative deviation from Raoult’s law.     (3 + 2)
Answer:
The law states that
Partial vapour presure of each volatile component in the solution is directly proportional to its mole traction.
Acetone + Chloroform or Nitric acid + water

Question 29.
a) The resistance of solution of a salt occupying a volume between two platinum electrodes 1.8 cm apart and 5.4 cm² in area was found to be 3 ohms. Calculate the conductivity of the solution.
Answer:
Conductivity = cell constant × conductance
\(\frac{1}{A} \times \frac{1}{R}\)
K = \(\frac{1.8}{5.4} \times \frac{1}{32}\) = 0.010425 cm^-1

b) Write the symbolic representation of standard hydrogen electrode and give its standard potential value. (3 + 2)
Answer:

Question 30.
a) Derive an integrated rate equation for the velocity constant for a first order reaction.
Answer:
Consider a first order reaction
R → P
A/c to Rate law, Rate = K [R]¹
∴Rate = \(\frac{-d[R]}{d t}\)
∴\(\frac{-d[R]}{d t}\) = K[R]
On rearranging, we got
\(\frac{d[R]}{d t}\) = -K dt
Integrating the equation, we get

Where I is the Integration constant
When t = 0, [R] = [R]₀
In [R]₀ =-k × o + I
I = In [R]₀
Where [R]0 is the initial con of the reactant ‘R’ substituting the value of I in equation (1)
We get In [R] = – Kt + In [R]₀
Kt = In [R]₀ – In [R]
Kt = In [R]₀/[R]

b) Draw a graph of concentration of R versus time for a zero order reaction. R → products. What is the intercept of the line? (3+2)
Answer:

[R₀] or Initial Concentration.

Question 31.
a) Give any three differences between physical adsorption and chemical adsorption.
Answer:
Physisorption:

1. It arises due to Vander waal’s forces
2. It is not specific in nature
3. It is reversible
4. Energy of adsorption is low

Chemisorption:

1. It arises due tb chemical bond formation
2. It is highly specific
3. It is irreversible
4. Energy of adsorption is high

b) What is
i) Tyndall effect ii) Peptisation?    (3 + 2)
Answer:
i) The phenomenon of scattering of light by the colloidal particles present in a colloidal solution is called Tyndall effect.
ii) The process of conversion of freshly prepared precipitate into a colloid by adding a suitable electrolyte is called peptization.

Part – D

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

Question: 32.
a) Explain i) Wurtz – Fittig reaction, ii) Swarts reaction with an example for each.
Answer:
i) Aryl halide reacts with alkeyl halide in the presence of sodium in dry other to form alkyl benzene.
Ex:

ii) An alkyl fluoride is obtained by heating an alkyl chloride or cromide in the presence of silver fluoride.
Ex: CH₃Br + AgF → CH₃F + AgBr

b) Which one of the following is more reactive towards Sn2 reaction?   (4 + 1)
CH₃E, (CH₃)₂ CHBr, (CH₃)₃ CBr
Answer:
CH₃Br

Question 33.
a) Explain the mechanism of dehydration of ethanol to ethene.
Answer:
The mechanism of dehydration of ethanol to ethene involves the following 3 steps.
Step – 1: Protonation of alcohol

Step – 2 : Formation of carbocation by loss of water.

Step – 3: Formation of ethene by loss of proton

b) How is salicylic acid converted into aspirin? Give equation.     (3 + 2)
Answer:
When phenol is treated with acetic anhydride in the presence of con.
H₂SO₄ aspirin is formed.

Question 34.
a) Benz Idehyde is treated with concentrated NaOH. Write the equation for the read on. Name the reaction and name any one product formed.
C₆H₅CHO + NaOH → C₆H₅COONa + C₆H₅CH₂OH
Cannizzaro’s reaction
Benzyl alcohol or Sodium benzoate.

b) Complete the following equations:

Question 35.
a) What is Hinsberg’s reagent? How is it used to distinguish primary amine from a secondary amine?
Answer:
Benzene sulphonyl chloride (C₆H₅SO₂ Cl) is called Hinsberg’s reagent.
Primary amine reacts with Hinsberg reagent to form a product soluble in an alkali.
Secondary amine reacts with Hinsberg’s reagent to from a product insoluble in an alkali.

b) Identify the major product in the following.
Answer:
i) C₂H₅NH₂ + CH₃COCl → C₂H₅NHCOCH₃

Question 36.
a) Write the Haworth’s structure of lactose.
Answer:

b) Mention any two importance of nucleic acids.
Answer:

1. DNA is the chemical basis of heridity
2. They are involved in the protein synthesis
3. It is the reserve of genetic information of different species. (Any two)

c) Name the hormone that contains iodine. (2 + 2 + 1)
Answer:
Thyroxine

Question 37.
a) How are polymers classified based on source?
Answer:
Based on the source polymers are classified as

1. Natural
2. Synthetic

b) Explain with equation, preparation of neoprene.
Answer:
Neoprene is formed by the free radial polynization of chloroprene

c) Name the dicarboxylic acid used as one of the monomer in the manufacture of terelene.   (2 + 2 + 1)
Answer:
Terephthacic Acid.
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