Central Academy

Annual Examination (2023-2024)

Class - XI

Time: 3 Hours

Subject-Chemistry (Set-B)

Full Marks: 70

General Instruction:

1. There are 33 questions in this question paper with internal choice.

2. SECTION A consists of 16 multiple choice questions carrying 1 mark each.

3. SECTION B consists of 5 very short answer questions carrying 2 marks each. 4. SECTION C consists of 7 short answer questions carrying 3 marks each.

5. SECTION D consist of 2 case-based question carrying 4 marks each.

6. SECTION E consists of 3 long answer questions carrying 5 marks each.

7. All questions are compulsory.

8. The use of log tables and calculator is not allowed.

Section-A

1. How much mL of water must be added to 200 mL of .65 M HCL to dilute the solution to 20 (M)

a) 450 mL

b) 400 mL

c) 350 mL

d) 500 mL

2. Pairing of electrons in the orbitals belonging to the same subshell (p, d or f) does not take place until each orbital belonging to that subshell is singly occupied. This is called

a) Pauli's exclusion principle

b) Aufbau principle

c) Hund's rule of maximum multiplicity

d) None of these

3. Maximum entropy will be in which of the following?

a) water vapour

b) snow

c) liquid water

d) ice

4. What is the magnetic quantum number of the orbital 2pz?

a) 1

b) ±1

c)-1

d) 0

5. The enthalpy of combustion of methane, graphite and dihydrogen at 298 K. are, - 890.3kJmo * l ^ - 1 , -3035 kJ mo * l ^ - 1 and -285.83. KJmo * l ^ - 1 respectively. Enthalpy of formation of C*H_{2} (g) will be

a) 74.8KJ / m * ol

b) 52.26kJ / m * ol

c) - 74.8kJ / m * ol

d) 0.42 * 0.27KJ / m * ol

6. The oxidation state of Cr in Cr (CO)6 is

a) 0

b) 2

c) 2

d) 6

7. Which of the following is not a redox reactions?

K 4 F C (CN) 8 +H 2 SO 4 +H 2 O K 2 SO 4 +CO+FeSO 4 + (N*H_{4}) * zS*O_{4}

CuSO 4 + N*H_{3} -> Cu(N*H_{3}) * 4S*O_{4}

Mg + N_{2} -> Mg*N_{2}

I_{2} + 3C*l_{2} -> 2IC*l_{3}

8. The structure of IF is

a. Pentagonal bipyramid

b. Square pyramid

c. Trigonal bipyramid

d. Octahedral

9. In which of the following process, the process is always non-feasible?

a) Delta*H > 0 triangle S > 0

b) Delta*H < 0 triangle S > 0

c) Delta*H > 0 triangle S < 0

d) Delta*H < 0 triangle S < 0

10. Which one of the following is isoelectronic with Ne?

a. M * g ^ 2 +

b. A * l ^ 3 +

N ^ 3-

d. All of these

1. When 2-butyne is treated with dil.H 2 S*O_{4} /HgSO 4 the product formed is

a. 1-Butanol

b. 2-Butanol

c. 2-Butanone

d. Butanal

12. Boiling point of alkanes

a. is independent of branching

b. decreases with increase in molecular mass

c. is independent of molecular mans

d. increases with increase in molecular mass

13. Assertion (A): Acetylene is acidic in nature.

Reason (R): Acetylene is sp hybridised.

a. Both A and R are true and R is the correct explanation of A.

b. Both A and R are true but R is not the correct explanation of A.

c. A is true but R is false.

d. A is false but R is true.

14. Assertion (A): Addition of HBr on propene in presence of peroxide give 1 bromopropaneas major product.

Reason (R): Addition of HBr on alkene proceed by carbocation intermediate

a. Both A and R are true and R is the correct explanation of A.

b. Both A and R are true but R is not the correct explanation of A.

c. A is true but R is false.

d. A is false but R is true.

15. Assertion (A): The radius of the first orbit of hydrogen atom is 0.529 Α.

Reason (R): Radius of each circular orbit is 0.529 A (n ^ 2 / (Z ^ 2))

a. Both A and R are true and R is the correct explanation of A.

b. Both A and R are true but R is not the correct explanation of A.

c. A is true but R is false.

d. A is false but R is true.

16. Assertion (A): Atomic mass has no unit but is expressed in amu.

Reason (R): It is the average mass is an atom taking care of the relative abundance of all is possible isotopes.

a. Both A and R are true and R is the correct explanation of A.

b. Both A and R are true but R is not the correct explanation of A.

c. A is true but R is false.

d. A is false but R is true.

Section- B

17. An alkene (molecular weight 56) on reaction with trioxygen followed by zinc, CH3COOHgave only ethanal Identify the Structure of the alkene.

Or

How will you convert benzene into

1) p- nitrobromobenzene

11) m-nitrobromobenzene

18. Oxygen is prepared by the catalytic decomposition of potassium chlorate (KCIO) Decomposition of potassium chlorate gives potassium chloride (KCI) and oxygen (O_{2}) If 2.4 moles of oxygen is needed for an experiment how many grams of potassium chlorate must be decomposed.

19. Find out the relation between heat capacity at constant temperature and heat capacity at constant pressure.

20. Lead chloride has a solubility product of 1.7 * 10 ^ - 5 at 298 K. Calculate its solubility at this temperature.

21. In each of the following pairs of salts, which one is more stable?

1. Ferrous and ferric salts

ii. Cuprous and cupric salts

Section - C

22. 100 ml. of a liquid is contained in an insulated container at a pressure of 1 bar. The pressure is steeply increased to 100 bar. The volume of the liquid is decreased by 1 ml. at this constant pressure: Find AH and AU.

23. Do the redox balance by ion-electron method of the following C*l_{2}(g)

+2OH^ - (aq) CIO^ * (aq) + C*Gamma(aq) + H_{2}*O(I)

24. Describe the change in hybridization (if any) of the Al atom in the following reaction, AlCl 3 + C*l_{2} AlCl^ +

25. (i) Give the mathematical expression of enthalpy.

(ii) Neither q nor W is a state function but a + W is a state function. Explain why?

26. Write down the electronic configuration of Na, Ne, C, Mg, F

Which of these have the lowest ionization enthalpy?

Which of these have the lowest electron gain enthalpy?

27. What transition in a hydrogen spectrum would have the same wavelength with Balmer transition series of n = 4 to n = 2 of He spectrum?

28. The reactant which is entirely consumed in traction is known as limiting reagent. In the reaction 2A + 4B -> 3C + 4D when 5 moles of A react with 6 moles of B, then

1. Which is the limiting reagent?

II. Calculate the amount of C formed.

Section - D

29. Read the text carefully and answer the questions:

The molecular orbital theory is based on the principle of a linear combination of atomic orbital. According to this approach when atomic orbitals of the atoms come closer, they undergo constructive interference as well as destructive interference giving molecular orbital, i.e, two atomic orbitals overlap to form two molecular orbitals, one of which lies at a lower energy level (bonding molecular orbital). Each molecular orbital can hold one or two electrons in accordance with pauli's exclusion principle and Hund's rule of maximum multiplicity.

Answer the following questions

1) Arrange the following stabilities of CN, CN+ and CN-in increasing order of bond.

II) The molecular orbital theory is preferred over valence bond theory. Why?

III) Ethyne is acidic in nature in comparison to ethene and ethane. Why is it so?Or

Bonding molecular orbital is lowered by a greater amount of energy than the amount by which antibonding molecular orbital is raised. In this statement correct?

30. Read the text carefully and answer the questions:

The existing large number of organic compounds and their ever-increasing numbers has made a necessary to classify them on the basis of their structures. Organic compounds are broadly classified as open-chain compounds which are also called aliphatic compounds. Aliphatic compounds further classified as homocyclic and heterocyclic compounds. Aromatic compounds are special types of compounds. Alicyclic compounds, aromatic compounds may also have heteroatom in the ring, Such compounds are called heterocyclic aromatic compounds. Organic compounds can also be classified on the basis of functional groups, into families or homologous series. The members of a homologous series can be represented by general molecular formula and the successive members differ from each other in a molecular formula by a CH2 unit

1) The successive members of a homologous series differ by which mass of amu? Is tetrahydrofuran is aromatic compounds?

II) Does Pyridine, pyrrole, thiophene are all heteroaromatic compounds?

III) Difference between heterocyclic and homocyclic compound?

Section - E

31. An alkyl halide C_{5}*H_{11} (A) reacts with ethanolic KOH to give an alkene 'B', which reacts with Brz to give a compound 'C', which on dehydrobromination provides an alkyne with 'D'. On treatment with sodium metal in liquid ammonia, one mole of 'D' gives one mole of the sodium salt of 'D' and half a mole of hydrogen gas. Complete hydrogenation of 'D' yields a straight-chain alkane. Identify A, B, C and D. Give the reactions involved.

Or

1) Write the structures and names of products obtained in the reactions of sodium with a mixture of 1- iodo-2-methylpropane and 2-iodopropane.

11) An unsaturated hydrocarbon "A" adds two molecules of H2 and on reductive ozonolysis gives butane-1,4-di-al, ethanal and propanone. Give the structure of 'A', write its IUPAC name and explain the reactions involved.

32. Calculate the degree of ionization of 0.05 M acetic acid if its pKa value is 4.74. How is thedegree of dissociation affected when its solution also contain

1) 0.01(M)

II) 0.1 (M) HCI

OR

Write a relation between Delta*G and Q and define the meaning of each term and answer the following

a. Why a reaction proceeds forward when Q<K and no net reaction occurs when Q=K?

b. Explain the effect of an increase in pressure in terms of reaction quotient for the reaction: CO(g) +

3H2 (g) rightleftharpoons CH * 4(g) + H_{2}*O(g)

33. Attempt any five of the following:

1)

Can a catalyst change the position of equilibrium in a reaction?

II) To which category of compounds does cyclohexane belong?

Write an IUPAC name: styrene.

IV) What is hydrogenation?

V) What are conformations?

VI) State Le chatelier's principle. Or

Calculate the pH of a solution formed by mixing equal volumes of two solutions A and B of a strong acid having pH = 6 and pH = 4 respectively.