Session Ending Examination (2015-16) Chemistry CLASS - XI

Time: 3 Hrs. M.M: 70

General Instructions:

Question 1 to 5 one mark.

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

Section A

1. In terms of ionisation enthalpy and electron gain enthalpy, what type of atoms combine to form an ionic compound?
2. For testing halogens in an organic compound with <math>AgNO_2</math> solution, sodium extract (Lassaigne’s test) is acidified with dilute <math>H NO_3</math>. What will happen if a student acidifies the extract with dilute <math>H_2SO_4</math> in place of dilute <math>HNO_3</math>?
3. What are the short comings of the Wurtz reaction?
4. What is the nature of oxides formed by most of p-block elements?
5. If atomic weight of C and S are 12 and 32 respectively, then an atom of S is ...... times heavier than an atom of C.

Section B

1. Out of N, and NH, which one will have greater value for van der Waals' constant 'a' and 'b'?
2. If the energy difference between the electronic states of hydrogen atom is 214.68 kJ <math>mol^{-1}</math> ,what will be the frequency of light emitted when the electron drops from the higher to the lower energy state?

(Planck's constant = <math>39.79 \times 10^{-14} \, kJ \, s \, mol^{-1}</math>)

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1. (i) Why is the first ionisation enthalpy of the transition elements reasonably constant?
2. Explain the trend in ionisation enthalpies for the noble gases.

1. Write the structure of the product of hydrolysis of <math>(CH_3)</math>, <math>SiCl_2</math> and its two uses.
2. A liquid with high boiling point decomposes on simple distillation but it can be steam distilled for its purification. Explain how is it possible?

Section C

1. What is an electrovalent bond (or ionic bond)? Explain its formation with two suitable examples.

1. Calculate the uncertainty in the position of an electron if uncertainty in its velocity is
2. 0.001%

1. zero.

(The mass of electron = <math>9.1 \times 10^{-31} kg</math>, velocity of electron = 300 <math>ms^{-1}</math>).

1. One mole of <math>CO_2</math> occupies 1.5 L at <math>25^{\circ}C</math> . Calculate the pressure exerted by the gas using
2. ideal gas equation.
3. van der Waals' gas equation with <math>a = 3.6L^2</math> bar <math>mol^{-2}</math> and <math>b = 0.04 L mol^{-1}</math>.
4. Arrange the following molecules in the decreasing order of oxidation state (+ ve to - ve) of nitrogen <math>NO_2</math>, <math>NH_3</math>, <math>HN_3</math>, <math>NO_2</math>, <math>N_2H_3</math>
5. Write three general characteristics of the elements of s-block of the periodic table which distinguish them from the elements of the other blocks.

16. To what type of system the following belong?

1. Tree
2. Pond
3. Animals
4. Tea placed in kettle
5. Tea placed in thermos flask
6. Ten placed in a cup.

1. The element 119 has not been discovered. What would be the IUPAC name and symbol

for this element? On the basis of the periodic table, predict the electronic configuration of this element and the formula of its most stable chloride and oxide.

1. What is the cause of acid rain? How is it harmful to the environment?

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