Chemistry NEB 2074 (old course) (grade increment) question paper

Group A

Very short answer questions(15 × 2 = 30)

1. 1.

   How many number of moles of $\mathrm{CO}$ will be left when $2\times 10^{21}$ molecules are removed from 0.28gm of $\mathrm{CO}$ ?

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2. 2.

   How does Dalton's atomic theory explain the law of conservation of mass.

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3. 3.

   Define surface tension and write its unit.

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4. 4.

   Differentiate between Crystalline solid and Amorphous solid with an example of each.

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5. 5.

   Name the quantum number that specifies the energy of an electron in an atom. What designation is given to an orbital having n=3 and $l=2$

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6. 6.

   Calculate the atomic number and number of p-electrons of an atom whose valence-shell electronic configuration is $4S^2$.

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7. 7.

   What is meant by nuclear fission reaction ? Write an example of it.

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8. 8.

   Write down the Lewis structure of i) $\mathrm{Na}{}_2\mathrm{S}{}_2\mathrm{O}{}_3$ ii) $\mathrm{O}{}_3$

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9. 9.

   $\mathrm{H}{}_2\mathrm{O}$ gets angular structure whereas $\mathrm{CO}{}_2$ gets linear. Why ?

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10. 10.

    Which ion would you expect to have smaller size and why ? $\mathrm{Mg}{}^{++}$ or $\mathrm{Na}{}^{+}$

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11. 11.

    Calculate the oxidation number of i) C in $\mathrm{HCOONa}$ ii) Cl in $\mathrm{KClO}{}_3$

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12. 12.

    What is the effect of increase of pressure and decrease of temperature in the following chemical equilibrium ? $2\mathrm{SO}{}_2(\mathrm{g})+\mathrm{O}{}_2(\mathrm{g})\rightleftharpoons 2\mathrm{SO}{}_3(\mathrm{g})+\mathrm{heat}$

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13. 13.

    Which one is more stable and why Ortho Hydrogen or Para Hydrogen.

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14. 14.

    How are chlorofluorocarbon responsible for the depletion of ozone layer ?

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15. 15.

    What is meant by allotropy ? Name the hardest allotrope of carbon and its use.

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16. 16.

    Give a balanced chemical reaction for the preparation of $\mathrm{PH}{}_3$ in the laboratory what happens when it is treated with $\mathrm{O}{}_2$

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17. 17.

    Define the terms: Gangue and Slag, giving proper example of each.

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18. 18.

    What happens when: i) Gypsum salt is heated at $120^{\circ }\mathrm{C}$ ii) Chlorine gas is passed through slaked lime.

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    2
19. 19.

    Write down IUPAC name of the following organic compounds. i) $(\mathrm{CH}{}_3){}_2\mathrm{C}=\mathrm{CH}-\mathrm{CHO}$ ii) $\mathrm{COOH}$ $\mathrm{COOH}$

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20. 20.

    Write an example of each of the followings: i) Baeyer's test ii) Wurtz reaction

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21. 21.

    Identify the major product $\mathrm{A}$ and $\mathrm{B}$ in the following reaction sequence. $\mathrm{CaC}{}_2\stackrel{\mathrm{H}{}_2\mathrm{O}}{\to }\mathrm{A}\stackrel{\mathrm{ammonical}\mathrm{AgNO}{}_3}{\to }\mathrm{B}$

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22. 22.

    What is the structural formula of ethanoic acid ? Write its functional isomer and IUPAC name.

    GROUP: B | Short answer questions | 5 × 5 = 25

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