SESSION ENDING EXAMINATION – (2014-15) Chemistry CBSE CLASS – XI

Time: 3 Hrs. M.M: 70

General Instructions:

1. Question 1 to 5 one mark.
2. Question 6 to 10 each two mark.
3. Question 11 to 22 each three mark.
4. Question 23 is value based question and carry four marks.
5. Questions 24 to 26 each five mark.

Q1 What do you understand by "Limiting reagent".

Q.2 State Hiesenberg Uncertainty Principle.

Q.3 The value of Vander was constants a and b are as given for two gases:

Gases <math>a(atm L^2 mol^{-1})</math> <math>b(mol^{-1})</math> C02 3.6 0.043 S02 6.7 0.056

Out of these = two gases which gas molecules will possess largest magnitude to intermolecular forces of attraction?

Q.4: In Lasssaigne's test for detection of nitrogen in an organic compound the blue colour appears due to the formation.

Q.5: For a reaction both enthalpy change and entropy change are positive. Under what conditions the reaction will be spontaneous?

Q.6 (i) How many subshells are associated with n=4?

1. How many electron will be present in the subshells having <math>m_z</math> value of -1/2 for n=4?

1/6

Q.7 (i) Define electron gain enthalpy.

1. Why is the electron gain enthalpy of chlorine more negative than fluorine?

Q.8 (i). In what group of the periodic table the element will found having electronic configuration:

<math>[Xe] 4f^{14} 5d^4 6s^2</math> [Xe] 4f 14 5d4 6s2

1. Why first ionization enthalpy of nitrogen is more than oxygen?

Q.9: Which out of <math>NH_z</math> and <math>NF_z</math> has higher dipole moment and why? OR Draw the molecular orbital diagram of dioxygen and calculate bond order.

Q.10 (i) Draw the structure of diborane.

1. <math>PbCl_{\perp}</math> is less stable than <math>SnCl_{\perp}</math> but <math>PbCl_{\perp}</math> is more stable than <math>SnCl_{\perp}</math>. Why?

Q.11 (i) CO, is a gas while SiO2 is solid at room temperature. Why?

1. <math>SiCl_4</math> can be easily hydrolysed but <math>CCl_4</math> does not hydrolysed.. Why?
2. Silicon shows a higher covalency than carbon. Why?

Q.12 An electron beam is accelerated by a potential difference of 10000 volts. What is the wavelength of the wave associated with the electron beam?

(mass of electron = <math>9.1 \times 10^{-31} kg</math>, Charge of electrons = <math>1.6 \times 10^{-19} C</math> OR Calculate the uncertainty in the velocity of a cricket ball of mass 150 g, if the uncertainty in its position is of the order of 1.40

<math>(h = 6.6 \times 10^{-34} \text{ Kg m}^2 \text{ s}^{-1})</math>

Q.13 (i) Draw the orbital structure of ethane.. 2/6