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 N₂molecule.	(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: 4HCl(aq) + MnO₂(s) 2H₂O (l) + MnO₂(aq) + Cl₂(g) How many grams of HCl react with 5.0 g of MnO₂? (OR) 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 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. 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: N^3-, O^2-, 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⁺²is 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. 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. 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^-3M, O₂= 4.2 x 10^-3M and NO = 2.8 x 10^-3 M in a sealed vessel at 800 K. What will be Kc for the reaction N₂(g) + O₂(g) 2NO(g)	(3)
26	Explain the hybridization involved in ethene molecule .	(3)
27	i)Define disproportionation reaction with an example. 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⁺, O₂^2- (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. 2NH₃ (g) +CO₂(g) NH₂CONH₂ (aq) + H₂O (l) 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: 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)