Chemistry – Important Questions Bank for Meghalaya Board (MBOSE) HSSLC 2016 Examination

Question – Short-answer Questions of 3 marks each. Answer these in about 40–50 words each.

Question – Long-answer Questions of 5 marks each. Answer these in about 70–80 words each.

1. An element X has f.c.c. lattice and edge of the unit cell is 400 pm. Find the distance between the nearest two X atoms and radius of the atom X.
2. Why does ZnO appear golden yellow at high temperature?
3. How is nickel purified by Mond’s process?
4. Give one example each of acidic flux and basic flux used in metallurgical processes.
5. Why are the graphite rods replaced periodically in the metallurgy of aluminium?
6. Write the chemical reactions taking place in the extraction of zinc from zinc blende.
7. How will you bring about the following conversions in not more than two steps?(i) Propanone to propane(ii) Benzoic acid to benzaldehyde
8. Although electron gain enthalpy of fluorine is less negative as compared to chlorine, fluorine is stronger oxidizing agent than chlorine. Why?
9. Dry chlorine does not act as a bleaching agent. Why?
10. Explain why the molecular mass of NaCl determined by the elevation of boiling point method is half its actual molecular mass
11. Give reason for ‘‘Addition of 1 mole of any volatile substance like methyl alcohol to 1 liter of water decreases the boiling point of the solution in comparison to pure water’’.
12.  How will you achieve the synthesis of only 4-bromoaniline from aniline without production of the trisubstituted aniline?
13.  Give two examples of amphoteric oxide.
14. Mention the conditions required to maximize the yield of ammonia in its synthesis by Haber’s process.
15. Which form of sulphur shows paramagnetism and why?
16. An element X has f.c.c. lattice and edge of the unit cell is 400 pm. Find the distance between the nearest two X atoms and radius of the atom X.
17. On addition of 0 . 643 g of a non-volatile compound to 50 ml of benzene (density = 0 879 g cm ^-3)  the freezing point is lowered from 5. 51 ᴼ C  to 5.03 ᴼ C. If K _f  for benzene is 5.12, find the molar mass of the non – volatile compound.
18. Define specific conductivity and molar conductivity for the solution of an electrolyte. How do they vary with dilution?
19. What is corrosion? Give the mechanism of rusting of iron.
20. Although electron gain enthalpy of fluorine is less negative as compared to chlorine, fluorine is stronger oxidizing agent than chlorine. Why?
21. Why is ICl more reactive than I2?
22. Nitrogen exists as diatomic molecule N2 and phosphorus as P4. Why?
23. Write the principle and conditions involved giving step wise reactions in the manufacture of H₂ SO₄ by contact process.
24. Prove that the time taken to complete 50% of a first-order reaction is independent of the initial concentration.
25. Write the balanced chemical equation for the reaction of Cl2 with hot concentrated NaOH. Is this reaction a disproportionate reaction? Justify.
26. OF2 should be called oxygen difluoride and not fluorine oxide. Why?
27. Why do Zr and Hf exhibit similar properties? What is the outermost electronic configuration of these   elements?
28. An iron oxide crystallizes in hcp array of oxygen with two out of three vacant octahedral voids occupied by iron. Give the formula of iron oxide.
29. What are calcination and roasting? In which type of ores are these processes used?
30. Write the chemical reactions involved in the blast furnace during the extraction of iron from haematite.
31. Write the chemical reaction of hydrogen sulphide with acidified potassium dichromate. Draw the structure of dichromate ion.
32. How is potassium permanganate obtained from pyrolusite ore? Write the structure of MnO ^–₄ ion.
33. Explain why aniline does not undergo Friedel-Crafts reaction?
34. Which linkage is present between the two units of monosaccharides in disaccharides? Name the disaccharide present in milk.
35. What is the effect of addition of non-volatile solute to the vapor pressure of a pure liquid? Give reasons for your answer.
36. Calculate the molar mass of a substance 1. 3 g of which when dissolved in 169 g of water gave the solution which will boil at 100.025 °C at 1 atm.  (K _b = 0.52 Km^-1)
37. State Henry’s law on solubility of gases in liquid. Why do we see effervescence when a cold drink bottle is opened?
38. Calculate the molarity and molality of a 15% solution (by weight) of H₂SO₄  of density 1.020 g cm^-3
39. Write down the preparation of ozone from oxygen. Mention the conditions required to maximize the yield of ozone.
40. Write the structural formula of PCl5 in solid state and also indicate the hybridisation of phosphorus atoms.

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