Session Ending Examination (2015-16) 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.

Section A

1. Arrange the following in the increasing order of their size <math>F^-</math>, <math>Li^-</math>, <math>Ne^-</math>, <math>Cl^-</math>.
2. Why are liquids like ether and acetone kept in cool places?
3. Why do trihalides of group 13 elements fume in the moist air?
4. What experimental support is available for de-Broglie's equation?
5. Why is second electron gain enthalpy (electron affinity) negative (i.e., energy is absorbed)?

Section B

1. Calculate the uncertainty in the velocity of a wagon of mass 3000 kg whose position is known to an accuracy of <math>\pm 10</math> pm. (Planck's constant = <math>6.63 \times 10^{-34}</math> Js.).
2. Draw the possible resonance structures for <math>CH_3 - \ddot{O} - \ddot{C}H_2</math> and predict which of the structures is more stable. Give reason for your answer.
3. On Illustrate the formation of bonding and antibonding molecular orbitals from atomic orbitals?

With the help of Le-Chatelier 's principle explain

1. we sweat more on a humid day.
2. clothes dry quickly on a windy day.
3. What is the role of red phosphorus in the reduction of alkyl halide using hydroidic acid?

Section C

1. Calculate the number of moles of nitrogen dioxide, <math>NO_2</math> that could be prepared from

0.35 mole of nitrogen oxide and 0.25 mole of oxygen.

<math>2NO(g) + O_2(g) \longrightarrow 2NO_2(g)</math>

Identify the limiting reagent and the excess reagent in the reaction. What would happen to the potential yield of <math>NO_2</math> if the amount of NO were increased? What, if the amount of <math>O_2</math> were increased?

12. (i) Which of the following ions is more stable?

Use resonance to explain your answer.

ČH₂ CH₂

1. (B)
2. What is the correct order of stability of the carbonium ion?

<math>(CH_3)</math>, <math>C^-</math>, <math>CH_3CH_3^-</math>, <math>CH_3^-</math>, <math>(CH_3)</math>, <math>CH_3^-</math> Or Resonance structures of propenal are given below. Which of these resonating structures is more stable? Give reason for your answer.

<math>CH_{\underline{s}} = CH - CH = O \longleftrightarrow CH_{\underline{s}} - CH = CH - O^{\odot}</math>

1. Draw the Lewis structures for the following ionic compounds.
2. Li₂O
3. CaC7.
4. LiF

1. The enthalpy change involved in the oxidation of glucose is - 2880 kJ <math>mol^{-1}</math>. 25% of this

energy is available for muscular work. If 100 kJ of muscular work is needed to walk one kilometer, what is the maximum distance that a person will be able to walk after Eating 120 g of glucose?

1. 0.1 mole of <math>N_2O_2</math> (g) was sealed in a tube under atmospheric conditions at <math>25^{\circ}C</math>

Calculate the number of moles of <math>NO_2(g)</math> present if the equilibrium <math>N_2O_4(g)2NO_2(g)</math> is 2/5