CBSE Half Yearly Sample Paper 2020-21 Chemistry For Class 11

Half Yearly Examination (2019-20)


Time-3:00 hours

Maximum Marks-70

General Instructions:

  • Questions 1 to20 are very short answer questions and carry 1 mark each
  • Questions 21 to 27 are short answer questions and carry 2 marks each.
  • Questions 28 to 34 are also short answer questions and carry 3 marks each.
  • Questions 35 to 37 are long answer questions and carry 5 marks each.

1. How much copper can be obtained from100gm of copper sulphate (CuSO4)?

2. Calculate the total number of electrons present in one mole of methane.

3. Draw the lewis dot structure of H2S, SiCl4.

4. Write the IUPAC name of atomic number 110 and 114.

5. Why do elements in the same group have similar physical and chemical properties?

6. Explain the physical significance of Vander Waals parameters.

7. Write the resonance structure for NO2, NO3-.

8. Explain why cations are smaller and anions are larger in radii than their parents atoms?

9. Compare the structures of H2O and H2O2.

10. What causes the temporary and permanent hardness of water?

11. For the process to occur under adiabatic conditions the correct condition is :

i) ΔT=0 ii)Δp=0     iii)q=0       iv)w=0

12. The enthalpies of all elements in their standard states are:

i) unity ii)zero       iii)<0         iv)different for each element

13. Which is the most abundant in the universe?

i) H ii)O            iii)N           iv) C

14. How many isotopes of hydrogen have?

i) 1 ii)2              iii)3            iv)4

15. What is the oxidation number of O in OF2?

i) -1 ii)-2            iii)+1                   iv)+2

16. Which element represents the standard electrode potential Zero?

i) Ag ii)Pb          iii)H                    iv) Sn

17. Which group elements are called chalcogens?

i) 14 ii)15           iii)16                             iv)17

18. How many electrons are present in Element Mg2+?

i) 12 ii)11           iii)10                             iv)13

19. What is bond angle between Water (H-O-H) formula?

i) 5 ii)104.5      iii)105.5              iv)108.5

20. Which type of hybridsation present in NH3?

i) sp ii)sp2         iii)sp3                 iv)sp3d

21. 1.Calculate the molarity of NaOH in the solution prepared by dissolving its 4g in enough water to form 250ml of the solution.

21.2. Calculate the mass per cent of different elements present in sodium sulphate (Na2SO4).

22. Determine the empirical formula of an oxide of iron which has 69.9% iron and 1% dioxygen by mass.

23. 1.What is the main differences between law of definite and multiple proportions?

23.2. Identify the substance oxidisied, reduced, oxidising agent and reducing agent in following reactions:

  1. N2H4+2H2O2 à N2 + 2H2O
  2. Pb+PbO2+2H2SO4à 2 PbSO4+2H2O

24. Define the term-

  1. Pauli Exclusion principle
  2. Hund’s rule of max. multiplicity

25.1.Calculate the wavelength of an electron moving with a velocity of 2.05 x 107ms-1.

25.2 The mass of an electron is 9.1 x 10-31If its K.E. is 3.0 x 10-25 J. Calculate its wavelength.

26. What are the various factors due to which the ionization enthalpy of the main group elements tends to decrease down a group?

27. Define the terms :-

i) Daniell cell ii) Standard Electrode potential

28.1. Write the general electronic configuration of s, p, d and f block.

28.2.What is the basic difference in approach between the Mendleev’s periodic law and the modern periodic law?

29. Explain the Rutherford’s famous alpha-particle scattering experiment with figure, conclusions and postulates.

30.1.Calculate the number of KJ of heat necessary to raise the temperature of 60.0g of Al from 35C to 55C. Molar heat capacity of all is 24Jmol-1K-1.

30.2.For the reaction, 2Cl(g)——-Cl2(g),What are the signs of ΔH and ΔS ?

31.1.What is the oxidation number? Write the rules to find the oxidation number.

31.2.Balance the following reaction by Half reaction:-

Fe+2  + Cr2O72-  ——— Fe+3  +   Cr+3

32.1.What are the main postulates of VSEPR theory? Explain briefly.

32.2.Define electro negativity. How does it differ from electron gain enthalpy?

33.1. Distinguish between A sigma and pi-bond. Also define hydrogen bond.

33.2.Define the Dalton’s law of partial pressure with mathematically expression.

34.1. Find The total number and The total mass of protons in 34mg of NH3 at STP.

34.2.Calculate the wavelength, frequency and wave number of a light wave whose period is 2.0 x 10-10

35.1. Define the terms

a) Extensive and intensive properties

b) Hess’s law of constant Heat Summation

c) Bomb calorimeter

35.2. Prove the relationship between Cp and Cv for an Ideal gas.

36. Define the terms:-

a) Electron-deficient hydrides

b) Electron-precise compounds

c) Electron-rich hydrides

d) Hydrogen Economy

e) Auto-protolysis of water


a) Calculate the temperature of 4.0 mol of a gas occupying 5dm3 at 3.32bar. (R=0.083bardm3k-1mol-1).

b) Calculate the total number of electrons present in 1.4g of di- nitrogen gas. (R=0.083 barLK-1mol-1).

37.2.A mixture of di-hydrogen and di-oxygen at one bar pressure contains 20% by weight of di-hydrogen. Calculate the partial pressure of di-hydrogen.

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