CBSE Chemistry Class 11 (Mid Term Exam Model Paper)

CLASS:XI CHEMISTRY

Duration: 3 hrs Maximum marks: 70

General Instructions:

All questions are compulsory.

i)Marks for each question are indicated against it.

ii)Question numbers 1 to 8 are very short answer questions and carry 1 mark each.

iii)Question numbers 9 to 18 are short answer questions and carry 2 marks each.

iv)Question numbers 1 9 to 27 are also short answer questions and carry 3 marks each.

v)Question numbers 28 to 30 are long answer questions and carry 5 marks each.

vi)Use logarithm tables if necessary. Use of calculator is not allowed.

Questions:-

1 Calculate the number of moles in 14g of N2 molecule. (1)
2 What would be the IUPAC and symbol for the elements with atomic numbers 121 and 113. (1)
3 Draw the Lewis dot structure of Nitrite ion (NO2-). (1)
4 What do you meant by bond length? (1)
5 Define coefficient of viscosity. What is its S.I. unit? (1)
6 Calculate the oxidation number of phosphorous in H3P2O7- and Au in HAuCl4. (1)
7 How the presence of H- ions be confirmed in ionic hydrides? (1)
8 What do you understand by the term hydrogen economy ? (1)
9 Chlorine is prepared in the laboratory by treating MnO2 with aqueous HCl according to the reaction:

clip_image001[4]4HCl(aq) + MnO2 (s) 2H2O (l) + MnO2(aq) + Cl2(g)

How many grams of HCl react with 5.0 g of MnO2?

(OR)

clip_image002[6]Calcium carbonate reacts with aqueous HCl to give CaCl2 and CO2 according to the reaction, CaCO3 (s) + 2HCl(aq) CaCl2 (aq) + CO2 (g) +H2O (l).

What mass of CaCO3 is required to react completely with 25ml of 0.75 M HCl?

Atomic mass of Mn=25,Ca=20

(2)
10 State and explain Dalton’s law of partial pressure. Prove that partial pressure of a gas is equal to the product of its mole fraction and total pressure in a gaseous mixture. (2)
11 At 250C and 760mm of Hg pressure, a gas occupies 600ml volume. What will be its pressure at a height where temperature is 100C and volume of the gas is 640ml. (2)
12 Write vander Waal’s equation for ‘n’ moles of a gas and mention the significances of vander Waal’s constants ‘a’ and ‘b’. (2)
13 i) What is black body radiation?

ii)Name two experiments each to prove the particle and wave nature of electromagnetic

radiation.

(2)
14 Calculate the enthalpy change of the following reaction

clip_image003[4]4NH3(g) + 5O2 (g) 6H2O(g) + 4NO(g)

Standard enthalpies of formation at 298 K for NH3(g), H2O(g) and NO(g) are -46.1, -2452

and -90.4KJ/mol .

(2)
15 How will you apply equilibrium constant ‘K’ to predict the direction of a reaction. (2)
16 Balance the following redox reaction by ion- electron method in acidic medium.

clip_image004[4]MnO4 (aq) + Br- (aq) MnO2(s) + BrO3(aq)

(2)
17 How will you remove the permanent hardness of water by Calgon process? (2)
18 Justify that H2O2 can function as an oxidizing as well as reducing agent in acidic medium. (any one reaction each.) (2)
19 A compound contains 4.07% hydrogen, 24.27% carbon and 71.65% chlorine. Its molar mass is 98.96g. What are its empirical and molecular formulas? (3)
20 i) What is photoelectric effect?

ii)The threshold frequency ‘ vo’ for a metal is 7.0 x 1014 s-1. Calculate the kinetic energy of

an electron emitted when radiation of frequency .v = 1.0 x 1015 s-1 hits the metal.

(3)
21 Account for the following:

a) Chlorine has more negative electron gain enthalpy than fluorine.

b) Consider the following species:

N3-, O2-, F-, Na+, Mg2+ and Al3+

i)What is common in them?

ii)Arrange them in the order of increasing atomic radii.

(3)
22 i)Configuration of ion M+2 is 1s2 2s2 2p5. What is the configuration of the atom M?

ii)The first member of a group of elements in the s- and p-blocks shows anomalous behavior

as compared to that of the subsequent members in the same group. Why?

iii)Explain why Beryllium has higher first ionization enthalpy than Boron?

(3)
23 If water vapour is assumed to be a perfect gas, molar enthalpy change for vapourisation of 1 mol of water at 1 bar and 1000C is 41KJ /mol. Calculate the internal energy change, when

i) 1 mol of water is vapourised at 1 bar pressure and 1000C.

ii) 1 mol of water is converted into ice.

(3)
24 i) State Le- Chatelier’s principle.

ii)Using Le- Chatelier’s principle , predict the effect of temperature and pressure for the

maximum yield of CO2.

clip_image005[4]clip_image006[4] 2CO (g) + O2(g) 2CO2(g) + heat

(3)
25 i)State law of chemical equilibrium.

ii)Derive a relationship between Kp and Kc for the following reaction.

clip_image007[4]clip_image008[4]N2(g) + 3H2(g) 2NH3(g)

(OR)

i)What is heterogeneous equilibrium? Give an example.

ii)At equilibrium, the concentrationof N2= 3.0 x 10-3 M, O2= 4.2 x 10-3 M and

NO = 2.8 x 10-3 M in a sealed vessel at 800 K. What will be Kc for the reaction

clip_image009[4]clip_image008[5]N2(g) + O2(g) 2NO(g)

(3)
26 Explain the hybridization involved in ethene molecule . (3)
27 i)Define disproportionation reaction with an example.

clip_image010[6]ii)Depict the galvanic cell in which the reaction Zn(s) + 2Ag(aq) Zn2+ + 2Ag(s) takes place.Further show:

a) which of the electrode is negatively charged.

b) the carriers of current in the cell

c) individual reaction at each electrode.

(3)
28 i)Mention the physical significance of Heisenberg’s uncertainty principle.

ii)What are the frequency and wavelength of a photon emitted during a transition from n= 5

state to the n=2 state in the hydrogen atom?

(OR)

i)State Hund’s rule of maximum multiplicity.

ii)The mass of an electron is 9.1 x 10-31kg. If its K.E. is 3.0 x 10-25J, calculate its wavelength?

(2+3)
29 i)Describe the hybridization involved in PCl5 molecule. Why are axial bonds longer than equatorial bonds?

ii)Compare the relative stabilities of the following species and indicate their magnetic

properties.

O2, O2+, O22-

(OR)

i)On the basis of VSEPR theory predict the shapes of :

a)NH4+ b) ClF3

ii)With the help of MO diagram show that triple bond is present between two nitrogen

atoms.

(2+3)
30 i)State Hesse’s law of constant heat summation.

ii)Derive the mathematical expression of first law of thermodynamics.

iii)Find out the value of equilibrium constant for the following reaction at 298 K.

clip_image011[6]clip_image004[5] 2NH3 (g) +CO2(g) NH2CONH2 (aq) + H2O (l)

clip_image012[4]Standard Gibbs energy change, r G0 at the given temperature is -13.6KJ/mol.

(OR)

i)Define standard enthalpy of formation with an example.

ii)Define standard enthalpy of combustion.

iii)Calclate the enthalpy change of the following reaction:

clip_image013 H2C = CH2 (g) + H2(g) CH3 – CH3(g)

The bond energies of C- H, C-C, C=C and H-H are 99. 83, 147 and 104 kcal respectively.

(2+3)
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