Question Paper of Chemistry | Grade XI 2071

Candidates are required to give their answer in their own words as far as practicable. The figures in the margin indicates full marks.

Time: 3 hrs | Full Marks: 75 | Pass Marks: 27

Group ‘A’

Attempt any fifteen questions. [15 X 2 = 30]

1. 12gm of carbon react with 4gm of hydrogen to produce 16gm of methane. Which chemical law do these data illustrate. State the law. [1 + 1]
2. How many number of gold atoms are present in 0.6gm of 18 carat gold. The 24 carat gold is taken as 100% pure gold. (atomic mass of gold = 197). [2]
3. Distinguish between crystalline and amorphous solid giving an example of each. [1 + 1]
4. Boiling point of liquid P and Q are 70°C and 90°C respectively. Which of the two has higher vapour pressure at 70°C? Give reason. [2]
5. Write the electronic configuration for the atom having atomic number 19. What are the values of n and l of its outermost electron? [1 + 1]
6. Which principle goes against the concept of Bohr’s fixed orbits? State the principle. [1 + 1]
7. What is thermonuclear reaction? Write an example of it. [1 + 1]
8. What is meant by intra-molecular hydrogen bonding? Give an example of it. [1 + 1]
9. Write down the Lewis structure of the compound formed by two elements A and B whose outermost electrons are represented by 3S² and 3S²3p⁵ respectively. [2]
10. Which one N or O has more electron affinity and why? [2]
11. Calculate the oxidation number of underlined atom in the following compounds: [1 + 1]

a) NH₄No₃
b) Cr₂O₇^-2

12. Define equilibrium constant(Kc). What would be the expression for Kc in the following reaction [1 +1]
C(s) + CO₂(g) ⇋  2CO(g)
13. Why is water an excellent solvent for polar substances? [2]
14. Give reason: [1 + 1]

a) Co₂ as an acidic oxide
b) Al₂O₃ as an amphoteric oxide

15. Name any two gaseous compounds of each which are responsible for: [1 + 1]

a) Photochemical smog
b) Green house effect.

16. Give balanced chemical equation for the preparation of [1 + 1]

a) Phosphine
b) Carbon-monoxide

17. What is meant by hydro metallurgy? Give an example of it[1 + 1]
18. Define the terms: [1 + 1]

a) Dead burnt plaster
b) Available chlorine

19. Give the IUPAC name of the following compounds: [1 + 1]

20. Identify the major product A and B of the following and write their IUPAC name. [2]

21. How would you detect the presence of sulphur in the organic compound? [1 + 1]
22. Define gasoline addative and give an example of gasoline addative. [1 + 1]

Group ‘B’

Attempt any five questions. [5 X 5 = 25]

23. Write the essential postulates of Bohr’s model of an atom. How does this model correct the defect of Rutherford’s atomic model? [4 + 1]
24. 8gm of pure calcium is treated with 50gm of pure HCl to give CaCl₂ and H₂: [1 + 1 + 1 +2]

a) Which is limiting reactant?
b) Calculate the mass of unreacted left over.
c) What mass of CaCl₂ will be formed?
d) How many moles of water will be produced if the whole H2 formed in the reaction react with O₂?

25. Distinguish between oxidant and reactant. Balance the following equation by oxidation number method. [1 + 4]

KMnO₄ + HCl → KCl + MnCl₂ + H₂O + Cl₂

26. Give a suitable reaction for the preparation of each of each of: [1 + 1 + 1 + 1 + 1]

a) Ethane
b) Ethyne
How does ethyne react with
i) Water
ii) Curprous chloride.
How would convert ethyne into ethane?

27. Give balanced chemical equation for the preparation of ammonia from nitrogen and hydrogen. What are the proper physical conditions for better yield of ammonia? Write the action of ammonia on: [1 + 1 + 1 + 1 + 1]

aa) Mercurous nitrate paper
b) CuSO4 solution
c) CuO

28. Write the chemistry of plaster of paris. [5]
29. Explain, how bromine is manufactured from carnallite? Why are halides found in sea water?