Haryana Bseh Class 11 Chemistry — Real Previous-Year Papers

Which of the following is not extensive properties? (a) Mass (b) Volume (c) Enthalpy (d) Density

Which of the following reactions has a value of ΔS° greater than zero? (a) N2(g) + 3H2(g) ⇌ 2NH3(g) (b) CuSO4(aq) ⇌ CuSO4(s) (c) NaCl(s) ⇌ Na⁺(aq) + Cl⁻(aq) (d) CaO(s) + CO2(g) ⇌ CaCO3(s)

Which of the following is not a general characteristics of equilibria involving physical processes? (a) Equilibrium is possible only in a closed system at a given temperature. (b) All measurable properties of the system remain constant. (c) All the physical processes stop at equilibrium. (d) The opposing processes occur at the same rate and there is dynamic but stable condition.

BF3 is a ................. acid.

Bohr's model failed to explain the spectrum of atoms other than .................

Oxidation number of chlorine (Cl) in ClO3⁻ is .................

Write ethane, ethene and ethyne in order of decreasing electronegativity of carbon in them.

Write IUPAC name of the following compound:

Write chemical equation for the preparation of butane by Wurtz reaction.

Assertion (A): In the Lassaigne's test for nitrogen in an organic compound, Prussian blue colour is obtained. Reason (R): Prussian blue colour is due to the formation of [Fe(SCN)]²⁺ during the test. (a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). (c) Assertion (A) is true, but Reason (R) is false. (d) Assertion (A) is false, but Reason (R) is true.

Assertion (A): It is not possible to separate Staggered conformation from Eclipsed conformation. Reason (R): The energy difference between the two extreme forms is very small. (a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). (c) Assertion (A) is true, but Reason (R) is false. (d) Assertion (A) is false, but Reason (R) is true.

Assertion (A): Boiling point of alkanes decreases with increase in molecular mass. Reason (R): Intermolecular Vander Waals forces increase with increase in molecular size or surface area of the molecules. (a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A). (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). (c) Assertion (A) is true, but Reason (R) is false. (d) Assertion (A) is false, but Reason (R) is true.

Express the result of following calculation to the appropriate number of significant figures: 4.27 × 0.07883 / 6.005 **OR** Calculate the number of atoms in each of the following: (a) 52 µHe (b) 52 g He

(i) State the principle that suggests the presence of only two electrons in an orbital. [1] (ii) Give reasons why chromium has electronic configuration 3d⁵ 4s¹ and not 3d⁴ 4s². [1]

Consider the following species: N³⁻, O²⁻, Na⁺, Mg²⁺ Al³⁺. (a) What is common in them? [1] (b) Arrange them in the increasing order of their ionic radii. [1]

For the equilibrium 2NOCl(g) ⇌ 2NO(g) + Cl2(g), the value of Kc is 3.75 × 10⁻⁶ at 1069 K. Calculate the value of Kp. **OR** (a) State Le Chatelier Principle. (b) What will be the effect of temperature change on the equilibrium constant of the following reaction? N2(g) + 3H2(g) ⇌ 2NH3(g), ΔH = ‒92.38 KJ mol⁻¹

Balance the following redox reaction by ion electron method (acidic medium): H2O2(aq) + Fe²⁺(aq) → Fe³⁺(aq) + H2O(l)

What is Heterolytic cleavage? Name the species formed during this process. **OR** What is metamerism? Write one example.

An alkene 'A' on ozonolysis gives a mixture of propanal and pentan-3-one. Write structure and IUPAC name of 'A'.

(i) State and explain Avogadro law. [2] (ii) Calculate the atomic mass (average) of chlorine using the following data: 35Cl — % Natural Abundance 75.77, Molar mass 34.9689; 37Cl — % Natural Abundance 24.23, Molar mass 36.9659. [1]

Among the second period elements, the actual ionization enthalpies are in the order: Li < B < Be < C < O < N < F < Ne. Explain, why: (i) Be has higher ionization enthalpy than B? [1.5] (ii) O has lower ionization enthalpy than N? [1.5] **OR** What is the basic difference between electron gain enthalpy and electronegativity? Electronegativity of F is more than that of Cl, but electron gain enthalpy of F is less than that of Cl. Explain.

(i) Use molecular orbital theory to explain why Be2 molecule does not exist? [1] (ii) Which out of NH3 and NF3 has higher dipole moment and why? [2] **OR** Define Octet rule and write its limitations.

What is meant by the conjugate acid-base pair? Find the conjugate acid/base for the following species: HNO3, CN⁻, HClO4 and CO3²⁻ [1+2]

In a special type of redox reaction an element in one oxidation state is simultaneously oxidised and reduced. (i) Identify the type of this reaction. [1] (ii) Explain the essential conditions for such a reaction to occur, with a suitable example. [2]

Case: The characteristics of an orbital are expressed in terms of three numbers called Principal quantum number (n), azimuthal quantum number (l), magnetic quantum number (Ml). These numbers are obtained from the solutions of the Schrodinger wave equation. Further, to represent the spin (rotation) of the electron about its own axis, a fourth quantum number, called spin quantum number has been introduced. Thus, a set of four quantum numbers which gives us complete information i.e. location, energy, the type of orbital occupied, shape and orientation of that orbital etc. about all the electrons present in an atom is called quantum numbers. Questions: (i) How many orbitals are associated with principal quantum number (n = 4)? [1] (ii) Using s, p, d notations, describe the orbitals with the following quantum numbers: (a) n = 2, l = 0 (b) n = 4, l = 3 [1] (iii) Explain Hund's rule of maximum multiplicity. [2] **OR** What is Aufbau rule? Why is 4s orbital filled before 3d?

Case: In order to explain the characteristic geometrical shape of polyatomic molecules like CH4, NH3, H2O etc. Pauling introduced the concept of hybridisation. According to him the atomic orbitals combine to form new set of equivalent orbitals known as hybrid orbitals. Unlike pure orbitals, the hybrid orbitals are used in bond formation. The phenomenon is known as hybridisation which can be defined as the process of intermixing of atomic orbitals of slightly different energies so as to redistribute their energies, resulting in the formation of new set of orbitals of equivalent energies and shape. For example one 2s and three 2p orbitals of carbon hybridise, there is the formation of four new sp3 orbitals. Questions: (i) Which hybrid orbital are used by carbon atoms (1, 2 and 3) in the following molecule? CH3–CH2–COOH (atoms numbered 1, 2, 3 left to right over CH3, CH2, COOH respectively) [1] (ii) Is there any change in hybridisation of B and N as a result of the following reaction? BF3 + NH3 → F3B.NH3 [1] (iii) In PCl5 molecule, why are the axial bonds longer than equatorial bonds? [2] **OR** Although geometries of NH3 and H2O molecules are distorted tetrahedral, bond angle in water is less than that of ammonia. Discuss.

(i) State and explain Hess's law. [2] (ii) For the reaction at 298 K, 2A + B → C, ΔH = 400 KJ mol⁻¹ and ΔS = 0.2 KJ K⁻¹ mol⁻¹. Considering ΔH and ΔS to be constant over the temperature range, at what temperature will the reaction become spontaneous? [2] (iii) For an isolated system, ΔU = 0, what will be ΔS? [1] **OR** (i) Explain the following terms: (a) Closed system (b) Intensive properties (c) Enthalpy of atomization [3] (ii) State and explain the first law of thermodynamics. [2]

What is electromeric effect? Explain its types with suitable examples. **OR** (i) Write the resonance structures of aniline and show the movement of electrons by curved arrow. [2] (ii) 0.3780 g of an organic chloro compound gave 0.5740 g of silver chloride in Carius estimation. Calculate the percentage of chlorine present in the compound. [2] (iii) Write the structural formula of the following: 2-bromo-4-ethyl-6-methylaniline [1]

(i) How will you convert benzene into: (a) p-nitrotoluene (b) m-nitrotoluene [2] (ii) Complete the following reactions: (a) CH3–CH2–CH=CH2 + HBr —(Benzoyl Peroxide)→ ? (b) CH3–C≡CH + H2O —(Hg²⁺/H⁺, 33 K)→ ? [2] (iii) What is Huckel Rule? [1] **OR** (i) What happens when 1,2-dibromopropane is treated with alcoholic KOH followed by reaction with Sodamide (NaNH2)? [2] (ii) Explain the directive influence of nitro group in benzene. Why is nitro group known as deactivating group? [3]