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Chemistry Question Paper ~ 2078

 sanjiv %289%29

Attempt all questions (11×1=11)

Rewrite the best alternative to the following questions.

1. Nitrogen reacts with oxygen to give N2O3 and N2O5 respectively. Which law of stoichiometry do this data illustrate?
a) law of reciprocal proportion
b) law of conservation of mass
c) law of multiple proportion
d) law of constant proportion.

2. Electron affinity of element is in the order
 a) F > Br>I>Cl
b) I>Br>Cl>F
c) F>Cl>Br>I
d) Cl > F > Br > I

3. Ozone is
a) isomer of oxygen
b) isotope of oxygen
c) allotrope of oxygen
 d) isotone of oxygen

4. Efflorescent solid
a) turns to liquid by absorbing moisture
b) absorb certain number of water of crystallization
c) have high vapor pressure than that of atmospheric pressure
d) have low vapor pressure than that of atmospheric pressure

5. The shape of BF3 molecule is trigonal planar with bond angle equal to 120 0 . It is due to
a. Sp3 hybridized B atom
b. Sp2 hybridized B atom
c. Sp hybridized B atom
d. dsp2 hybridized B atom

6. The exact temperature, —273.15 0C is called absolute zero temperature at which
a. liquid molecules turns to gas
b. gaseous molecules do not exist
c. solid substance do not exist
d. expansion of volume of gas takes place

7. The gas that combines with hemoglobin to damage its oxygen carrying capacity is
a) CO2
b) CO
c) N2
d) O2

8. Ethanol is soluble in water. It is due to
a) Intramolecular hydrogen bonding
b) Vander Waals force of attraction. 
c) Intermolecular hydrogen bond
d) Co ordinate covalent bond

9. The first organic compound synthesized in laboratory from its constituents element is-
a) methane
b) acetic acid
c) urea
d) ethylene.

10. Propene reacts with HBr to give 2-bromopropane as major product. The addition reaction follows
a) Anti Markovnikove’s rule
b) Markovnikove’s rule
c) kekule’s rule
d) none of the above.

11. Which of the following is not related to continues process?
a) involves sequence of steps followed in specific order
b) requires high cost equipment
c) can’t be controlled easily
d) generally available in fully automated plant. 

Group 'B'

1. 10 gram of 80 % pure calcium is allowed to react with 0.6 mole of HCl to get CaCl2 and H2 gas.
i. Which is limiting reagent in the reaction and why? [2]
ii What is the importance of limiting reagent in stoichiometric calculation ? [1]
iii. Calculate the number of gram mole of salt formed. [1]
iv. What mass of water is formed when the hydrogen formed in the reaction reacts completely with oxygen? [1]

2. Establish the relation, P= P1 + P2 +P3 where P, P1, P2 and P3 have their usual meaning. 1 gram of CO2, 2 gram of N2 and 3 gram of O2 are placed in an evacuated cylinder of one litre capacity at normal temperature. Find the total pressure exerted by the mixture of gases. [2.5+2.5]

3. Discuss the application of Le Chatelier’s principle for the manufacture of ammonia by Haber’s process. [5]

OR

How did the Bohrs atomic model overcome the limitations of Rutherfords atomic model? Point out the limitations of Bohrs atomic model. [ 4+1]

4. Concentrated sulphuric acid can be used in laboratory to produce hydrogen chloride gas by the reaction with sodium chloride.
i. Hydrogen iodide is not produced by same method as for hydrogen chloride why? (1)
ii. How is it prepared? Give the balanced chemical equation also. [2]
iii. Compare the bleaching action of chlorine and sulphur dioxide [2]

5. Most of the metals are found in combined state in nature. So different metallurgical steps need to be followed to get pure metal from the ore.
i) Give the main steps to get pure metal from its sulphide ore. [2.5]
ii) How does ore differ from mineral? [1.5] iii) What is the importance of flux in metallurgy? [1]

6. One of the jars is filled with ethene gas and other is filled with ethyne gas.
i. Suggest any suitable test to distinguish between them. [2]
ii. What happens when ethene is treated with ozone followed by hydrolysis with Zn dust and water?[1]
iii. What happens when acetylene is heated in Cu tube? How does the product thus obtained obeys Huckle’s rule? [2]

7. A homologous series of alkyl halide is written as

CH3Cl
 CH3CH2Cl
CH3CH2CH2Cl
i. Define homologous series. [1]
ii. Give any two properties of homologous series. [1]
iii. What happens when the second member is heated with sodium metal in presence of dry ether? [1]
iv. How foreign element present in the third member is detected? Why it is necessary to prepare sodium extract? [2]


8. Urea is the most demanded chemical fertilizer in agricultural country like Nepal.
i) Give the principle reaction and labeled diagram for the manufacture of urea. [1.5+ 2]
ii) Discuss the main challenge of establishing chemical industry in Nepal. [1.5]

Group ‘C’

Attempt all questions. (3×8=24)

9. Michael Faraday studied the quantitative aspects of electrolysis and postulated two famous law named after him.
a. Define the term electrolytes and electrolysis. [2]
b. State first law of electrolysis. [1]
c. Electricity is passed through the two different electrolytic cells connected in series, containing CuSO4 and AgNO3 to deposit Ag and Cu. Which will deposit more? Give reason. (Atomic mass of Ag = 108, Cu= 63.5) [2]
d. Balance the following equations by oxidation number method OR ion electron method.

point out the oxidizing and reducing agent in this reaction. [2+1]

10. Sodium is extracted by electrometallurgy by Down’s process.
i. Why sodium metal cannot be obtained by chemical reduction method? [1]
ii. Write down the principle involved in Down’s process. [2]
iii. Sketch the Down’s cell [2]
iv. What are the difficulties in this process and how it is removed? [1]
v. Write the action of sodium with ammonia and give its one biological importance. [2]

OR
a) Write the principle of contact process for manufacture of sulphuric acid also draw the flow sheet diagram for the process. [3+3]
 b) Give a chemical equation in which sulphuric acid act as :
 i. dehydrating agent and ii) oxidizing agent. [1+1]

11. a) structural isomers have same molecular formula but different structure.
i) Give the structure and IUPAC name of functional isomer of ethanoic acid. [1]
ii) How does structural isomer differ from geometrical isomer? [2]
b) Define the followings:
i) octane number ii) carbonation iii) cracking [1+1+1]
c) Give the structure and name of A and B in the following reaction sequence: [1+1]

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