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. Is the law of constant composition true for all types of compounds? Mention why or why not?
2. What was the necessity for the classification of the elements?

1. Water decomposes by absorbing 286.2 kJ of electrical energy per mole. When <math>H_2</math> and <math>O_2</math>

combine to form one mole of <math>H_2O</math> , 286.2 kJ of heat is produced. Which law is proved? What statement of the law follows from it?

1. Which d-orbital does not have four lobes and what is its shape called?
2. Which species is the smallest aromatic substance?

Section B

1. Give two reactions to show acidic character of alkynes?
2. Calculate the mass of
3. an atom of silver (atomic mass = 108).
4. 1 molecule of naphthalene <math>(C_{10}H_{5})</math>.
5. (i) What did Thomson's experiment on the deflection of cathode rays yield?
6. What experiment neglected Thomson's model of the atom as an intimate mixture of

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negative and positive part?

9. Rank the following in the order of increasing entropy.

1. 1 mole of <math>H_1O(l)</math> at <math>25^{\circ}C</math> and 1 atm pressure.
2. 2 moles of <math>H_2O(s)</math> at <math>0^{\circ}C</math> and 1 atm pressure.
3. 1 mole of <math>H_1O(v)</math> at <math>100^{\circ}C</math> and 1 atm pressure.
4. 1 mole of <math>H_2O(l)</math> at <math>0^{\circ}C</math> and 1 atm pressure.
5. Radius of the fourth orbit in hydrogen atom is 0.85 nm. Calculate the velocity of the electron in this orbit (mass of electron <math>9.1 \times 10^{-31} \, kg</math>).

Section C

1. Calculate the wavelength of the spectral line obtained in the spectrum of <math>Li^{2-}</math> ion when

transition takes place between two levels whose difference is 2 and the sum is 4?

Calculate the oxidation number of

1. N in NO;
2. P in <math>H_3P_3O_7</math>
3. C in CO3-
4. 0 in <math>OF_2</math>
5. Cl in ClO.
6. Cr in Cr.O-
7. (i) Name the classes of hydrides to which <math>H_2O</math>, <math>B_2H_5</math>, CrH and NaH belong.
8. What do you mean by hydride gap?
9. Calculate the work of expansion when 100 g of water is electrolysed at a constant pressure of 1 atm and temperature of 25°C
10. Standard enthalpy of vaporisation of benzene at its boiling point is 30.8 kJ <math>mol^{-1}</math>. For how long would a 100 W electric heater have to operate in order to vaporise a 100 g sample

of benzene at its boiling temperature (power = <math>\frac{energi}{100}</math> -1W = <math>\frac{1}{100}</math>)? time

1. Discuss the various reactions that occur in the Solvay process.
2. Write three physical and three chemical properties of carbon monoxide.
3. What are cycloalkanes? Give the name, structural and the condensed formula of the first

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