Class 11 Question Paper (Two)

11 Chemistry

HALF YEARLY EXAMINATION 2020-21

CLASS-XI                                                                  MAX.MARKS:70

SUB: CHEMISTRY                                                              TIME: 3Hrs

General Instructions:

Read the following instructions carefully.

a) There are 33 questions in this question paper. All questions are compulsory.

b) Section A: Q. No. 1 to 16 are objective type questions. Q. No. 1 and 2 are passage based

questions carrying 4 marks each while Q. No. 3 to 16 carry 1 mark each.

c) Section B: Q. No. 17 to 25 are short answer questions and carry 2 marks each.

d) Section C: Q. No. 26 to 30 are short answer questions and carry 3 marks each.

e) Section D: Q. No. 31 to 33 are long answer questions carrying 5 marks each.

f) There is no overall choice. However, internal choices have been provided.

g) Use of calculators and log tables is not permitted.

SECTION – A

1.Read the given passage and answer the questions 1 to 4 that follow:

Pressure in well inflated tyres of automobiles is almost constant, but on a hot summer day this increases considerably and tyre may burst if pressure is not adjusted properly. During winters, on a cold morning one may find the pressure in the tyres of a vehicle decreased considerably.

i. The mathematical relationship between pressure and temperature is

    a) P1/T1 = P2/T2 at constant volume

    b) P1T1 = P2T2 at constant pressure

  c) P1/T1 = P2/T2 at constant pressure

 d) P1T1 = P2T2 at constant volume

ii. Who was given the mathematical relationship between pressure and temperature?

    a) Charle

    b) Avogadro

  c) Boyle

 d) Gay Lussac

iii. The pressure in the tyres of a vehicle decreased considerably in winter days

a) Due to Avogadro’s Law

 b) Due to Gay Lussac’s Law

c) Due to Boyle’s Law

d) Due to Charle’s Law

iv. Tyres of automobiles bursting in summer days

a) Due to Avogadro’s Law

b) Due to Gay Lussac’s Law

c) Due to Boyle’s Law

d) Due to Charle’s Law

2. Read the given passage and answer the questions 1 to 4 that follow:

It is clear that octet rule is based upon the chemical inertness of noble gases. However, some noble gases (for example xenon and krypton) also combine with oxygen and fluorine to form a number of compounds like XeF2, KrF2, XeOF2etc.

i. The number of lone pairs on Xenon atom in XeOF2 molecules

 a) 1

 b) 2

c) 3

d) 4

ii. The structure of XeF2 is

a) Linear 

b) Triangular

c) Pyramid

d) Bent 

iii. In which of the following have odd octet?

a) NO2

b) NO

c) a and b

    d) N2O4

iv. Which of the following have octet?

a) SiCl4

b) CCl4

c) CH4

d) All

Questions 3 to 11 are multiple choice questions and carry 1marks each.

3. How much volume of one mole of a gaseous substance occupies at STP?

     a) 22.4 L

     b) 22.2 L

c) 22.5 L

d) 22.7 L

4. The 2px, 2py and 2pz orbitals of an atom have identical shapes but differ in their …

     a) Volume

     b) Mass

     c) Orientation    

d) Charge

5. Name the most electronegative element in the long form of periodic table?

     a) Carbon

     b) Nitrogen

     c) Oxygen

d) Fluorine

6. How much time would it take to distribute one Avogadro number of wheat grains,if 1010 grains are distributed each second?

a) 6.022*1013

b) 6.022*1033

c) 6.022*1014

d) 6.022*1034

7. The enthalpy change for a reaction does not depend upon the

  1. Physical states of reactants and products.
  2. Use of different reactants for the same product.
  3. Nature of intermediate reaction steps.
  4. Difference in initial and final temperatures of involved substances.

8. The set representing the correct order of ionic radius is

  1. Li+1>Be2+> Na+1> Mg2+
  2. Na+1> Li+1> Mg2+> Be2+
  3. Mg2+> Be2+> Li+1> Na+2
  4. Li+2> Na+1>  Mg2+> Be2+

9. The number of molecules in 32g of oxygen is,

  1. 3.2×1016
  2. 6.02×1023
  3. 3.2×1023
  4. 6.02×1010

10. Which one of the following groupings represents a collection of isoelectronic species?

  1. Na+,Ca2+,Mg2+
  2. Be,Al3+, Cl–
  3. Ca2+,Cs+, Br
  4. N3-,F–, Na+

11. Which among the following factors is the most important in making fluorine the strongest oxidizing halogen?

  1. Electron gain enthalpy
  2. Bond dissociation energy
  3. Hydration enthalpy
  4. Ionization enthalpy

In the following questions (Q. No. 12 – 16) a statement of assertion followed by a statement of

reason is given. Choose the correct answer out of the following choices.

(A) Both assertion and reason are correct statements, and reason is the correct explanation of the assertion. 

(B) Both assertion and reason are correct statements, but reason is not the correct explanation of the assertion. 

(C) Assertion is correct, but reason is wrong statement. 

(D) Assertion is wrong, but reason is correct statement.

12. Assertion (A):  Pure water obtained from different states of India always contains    hydrogen   and oxygen in the ratio of 1:8 by mass.

Reason(R): Total mass of reactants and products during chemical change is always the same.

13. Assertion (A):  The ionization energy of nitrogen is more than that of oxygen.

Reason(R): Electronic configuration of nitrogen is more stable due to half-filled 2p orbitals.

14. Assertion (A):  Van der Waal’s equation is applicable only to non-ideal gases.

           Reason(R): Ideal gases obey the equation PV = nRT.

15. Assertion (A):  All molecules of an ideal gas more with the same speed.

           Reason(R): There is no attraction between the molecules in an ideal gas.

16. Assertion (A):  Enthalpy of graphite is lower than that of diamond.

           Reason(R):  Entropy of graphite is higher than that of diamond.

SECTION – B

The following questions, Q.No 17 – 25 are short answer type and carry 2 marks each.

17. Calculate the mass of 1*1022 molecules of CuSO4.5H2O.

18. The element Z = 117, If have not yet discovered. In which group and period would you place and also give the electronic configuration?

19. What is the total numbers of orbitals and electrons for m=o, if there are 30 protons in an atom?

20. Bond dissociation energy of F2 is less than that of Cl2. explain.

OR

 (a) Why chlorine has higher electron gain enthalpy than fluorine? 

 (b) Why Nitrogen has higher first ionization potential than oxygen atom?    

21. Assign oxidation number to the bold  elements in each of the following species:

 (a) NaH2PO4 (b)  K2MnO4 (c) CaO2 (d) CrO4– 

OR

What is Disproportination reactions ? illustrate with one example.

22. 10 g of O2 were introduced into an evacuated vessel of 5 litre capacity maintained at 27°C. Calculate the pressure of the gas in atmospheres in the container.(R = 0.083 L atm K-1mol–)

23. What is the concentration of sugar (C12H22O11) in mol L-1if its 20 g are dissolved in enough water to make a final volume up to 2 L?

24. A substance on analysis gave the following percentage composition: Na = 43.4%, C = 11.3%,  and O = 45.3%. Calculate the empirical formula (Atomic weight of Na = 23, c = 12, O = 16)

25. (i) Define Ideal gas.

 (ii) Using the equation of state PV = nRT show that at a given temperature, the density of the gas is proportional to the gas pressure P.

SECTION – C

Q.No 26 -30 are Short Answer Type II carrying 3 mark each.

26. From the following sets of quantum numbers, State which are possible. Explain why the others are not permitted?

a. n = 0, l = 0, m = 0, s = +1/2

b. n = 1, l = 1, m = 0, s = +1/2

c. n = 1, l = 0, m = +1, s = +1/2

d. n = 0, l = 1, m = -1, s = -1/2

e. n = 2, l = 2, m = 0, s = -1/2

f. n = 2, l = 1, m = 0, s = -1/2

OR

State the following; 

           a. Hund’s Rule,

           b. Pauli’s Exclusion Principle and

           c. Aufbau’s Principle.

27. a) Define the term Entropy. 

b) Predict the sign of entropy change for 

i) C (graphite) + O2 ——→  CO2 (g) 

ii) H2O (l) —————→  H2O(g) 

28. The value of Kc = 4.24 at 800K for the reaction,

CO (g) + H2O (g) –🡪CO2 (g) + H2 (g)

Calculate equilibrium concentrations of CO2, H2, CO and H2O at 800 K, if only COand H2O are present initially at  concentrations of 0.10M each.

OR

Write short notes on  i) common ion effect  ii) Solubility product iii) ionic product of water

29. a. Why vegetables are cooked with difficulty at a hill station?

           b. Why are falling liquid drops spherical?

c. Why a pressure cooker reduces the cooking time?

30. Balance the following redox reaction by ion – electron method : 

        MnO4 – (aq) + SO2 (g) —🡪 Mn2+ (aq) + HSO4 – (aq) (in acidic solution)       

SECTION – D

Q.No 31 to 33 are long answer type carrying 5 marks each.

31. Write the molecular orbital configurations of species: (a) N2 (a) N2+ (a) N2– (d) N22-

(i) Calculate their bond orders 

(ii) Predict their magnetic nature.

(iii) Arrange in increasing order of stability.

OR

i)Predict the hybridization and shape of the following molecules:

           (a) NH3 (b) BeCl2     (c) CO32-   

ii) Predict the geometry and shape of following based VSEPR theory 

  1.  H2O       b) ClF3

32. i) state Le chatlier principle

ii)Dihydrogen gas is obtained from natural gas by partial oxidation with steam as

per following endothermic reaction:

CH4 (g) + H2O (g) ⇌ CO (g) + 3H2 (g)

(a) Write as expression for Kp for the above reaction.

(b) How will the values of Kp and composition of equilibrium mixture be affected by

(i) increasing the pressure

(ii) increasing the temperature

(iii) adding catalyst

OR

a) What is meant by the conjugate acid-base pair? Find the conjugate acid/base

for the following species:

                                       HNO2,    CN–,    HClO4,        F –.

b) Calculate pH of a 1.0 × 10–8M solution of HCl. 

33a)State Hess Law. 

b)Calculate the standard enthalpy of formation of CH3OH from given data: 

(i) CH3OH (l) + 3/2 O2(g)  —🡪 CO2(g) + 2H2O ΔH = – 726 kJmol ̶ 1 

(ii) C (s)+ O2(g)—–🡪CO2(g) , ΔH = – 393kJmol ̶ 1 

(iii) H2(g) + 1/2 O2 (g) —-🡪H2O , ΔH = – 286kJmol ̶ 1 

OR

  1. State second law of thermodynamics
  2. State third law of thermodynamics
  3.  For the reaction at 298 K,   2A + B → C

 ∆H = 400 kJ mol–1 and ∆S = 0.2 kJ K–1 mol–1 At what temperature will the reaction become spontaneous considering ∆H and ∆S to be constant over the temperature range..

THE END

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