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Friday, 18 December 2015

CHEMISTRY (Theory) sample paper2 Class – XI

                                               CHEMISTRY (Theory)
                                                     Class – XI
Time allowed: 3 hours                                                                     Maximum Marks: 70
General Instructions:
a) All the questions are compulsory.
b) There are 26 questions in total.
c) Questions 1 to 5 are very short answer type questions and carry one mark each.
d) Questions 6 to 10 carry two marks each.
e) Questions 11 to 22 carry three marks each.
f) Questions 23 is value based question carrying four marks.
g) Questions 24 to 26 carry five marks each.
h) There is no overall choice. However, an internal choice has been provided in one question of two marks, one question of three marks and all three questions in five marks each. You have to attempt only one of the choices in such questions.

i) Use of calculators is not permitted. However, you may use log tables if necessary.

1. What is the maximum number of electrons in f subshell with same spin?
2. Two litres of an ideal gas at a pressure of 10 atm expands  isothermally into a vacuum until its total volume is 10 litres. How much heat is absorbed and how much work is done in the  expansion?
3. “BeH2 molecule has zero dipole moment although the Be-H bonds are polar” Explain.
4. Give water gas shift reaction.
5. Arrange the following metals in the order in which they displace each other from the solution of their salts. Al, Cu, Fe, Mg and Zn.
6. What is hydride gap? Why is heavy water used in nuclear reactors?
7. Though carbon dioxide is inert and harmless gas, it is thought to be a serious pollutant. Why?
8. Which of these electrons experience lowest effective nuclear charge?
a) The Br atom containing 35 electrons in which 6 electrons are in 2p orbital or
b) 6 electrons in 3p orbital and 5 electrons in 4p orbital.
9. Write structural formulas of the following compounds :
a) 3, 4, 4, 5–Tetramethylheptane
b) 2,5-Dimethyhexane
Or
Write the structural formula of:
a) O-Ethylanisole
b) 2,3 - Dibromo -1 - phenylpentane
10.
a) How change in velocity of a moving particle change the wavelength of the particle?
b) Give the difference in the angular momentum of an electron present in 3p and 4p orbitals?
11. A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The
volume of the container is suddenly increased.
a) How do rates of evaporation and condensation change initially?
b) What is the initial effect of the change on vapour pressure?
12.
a) How would you distinguish between BeSO4 and BaSO4?
b) Which is thermally most stable alkaline earth metal carbonate among MgCO3, CaCO3, SrCO3,
BaCO3? Give reasons.
13. Derive the structure of :
a) 2-Chlorohexane
b) Pent-4-en-2-ol
c) 3- Nitrocyclohexene
d) Cyclohex-2-en-1-ol
Or
Why NH3 has a higher dipole moment than NF3?
14. Why is the entropy of a substance taken as zero at 0 K? calculate the standard Gibbs free energy
change for the reaction
N2 (g) + 3H2 (g)Û2NH3 (g) at 298 K.
The Value of equilibrium constant for the above reaction is 6.6 x 105. [ R=8.314 J K-1 mol-1]
15. Define the following:
a) Critical temperature
b) Avogadro law
c) Charles Law
16. What happens when
a) Sodium metal is dropped in water?
b) Sodium metal is heated in free supply of air?
c) Sodium peroxide dissolves in water?
17. Justify giving reactions that among halogens, fluorine is the best oxidant and among hydrohalic
compounds, hydroiodic acid is the best reductant?

19. Explain the principle of paper chromatography?
20. Write a brief note on the following environmental terms:
i) Acid rain
ii) Eutrophication
iii) Green Chemistry
21.
i) List two differences between Orbit and Orbital
ii) If an electron is moving with a velocity 600 m/s which is accurate up to 0.005%nthen
calculate the uncertainty in its position. [ h=6.626 x 10-34 Js and mass of electron = 9.11 x 10-
31 kg]
22. Explain in brief for the following:
i) Anions are bigger in size than their parent atom.
ii) Oxygen has lesser first ionization enthalpy than nitrogen
iii) Fluorine has less negative electron gain enthalpy than chlorine
23. John was arrested by the custom officials as he was smuggling drugs and caught by x-ray
machines. According to Roentgen when electrons strike a material in the cathode ray tube, it
produces a ray which can cause fluorescence in the fluorescent material placed outside the
cathode ray tubes. These rays were called x-rays. These were not deflected by electric and
magnetic field. It was used as diagnostic tool in the treatment of diseases and bone fractures.
a) What is the approx. wavelength of x-rays?
b) Why x-rays are used to screen luggage’s in airports?
c) How would you prevent smuggling?
24.
a) The species H2O, HCO3, HSO4- and NH3 can act both as Bronsted acids and bases. For each case
give the corresponding conjugate acid and base.
b) Consider the following endothermic reaction: 4 2 2 CH (g) + H O (g)⇌CO (g) + 3H (g)
i) Write expression for Kp for the above reaction.
ii) How will the equilibrium be affected by?
1. Increasing the pressure 2. Using a catalyst
Or
a) Predict the acidic, basic or neutral nature of the following salt: NaCN, KBr, NaNO2, NH4NO3.
b) How many grams of KBr are added to 1 L of 0.05 M solution of silver nitrate just to start the precipitation of AgBr? Ksp of AgBr = 5.0 x 10-13
25. With the help of structures, give the IUPAC names of different chain isomers of alkanes
corresponding to the molecular formula C6H14.
Or
The preparation of acetaldehyde by passing mixture of ethene and oxygen under pressure into
aqueous solution of PdCl2 and CuCl2 as a catalyst is called Wacker’s process. Acetalydehyde is a
useful chemical which is used for silvering of mirror. It can be prepared by various methods. It is
used in the commercial preparation of acetic acid, ethyl acetate etc. Paraldehyde, a trimer of
aldehyde is used as hypnotic. a) Give the best method to prepare acetaldehyde. Give two reasons.
b) Give the chemical equation for Wacker’s process of preparation of acetaldehyde.
c) Give the disadvantage of preparing it from ethyne.
26. Give the net ionic equation for the reaction of potassium dichromate (VI) with sodium sulphite in
an acid solution to give chromium (III) ion and the sulphate ion.

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