#### 12th Standard English Medium Chemistry Reduced Syllabus Three mark Important Questions - 2021(Public Exam )

12th Standard

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Chemistry

Time : 01:00:00 Hrs
Total Marks : 75

Part A

25 x 3 = 75
1. Explain zone refining process with an example using the Ellingham diagram given below

2. Explain calcination with an example.

3. Copper and silver lie low in the electrochemical series and yet they are found in the combined state as sulphides in nature. Comment.

4. Describe the structure of diborane

5. Describe the structure of diamond.

6. How will you prepare chlorine in the laboratory?

7. Why do noble gases form compounds with fluorine and oxygen only?

8. Calculate the number of unpaired electrons in Ti3+ , Mn2+ and calculate the spin only magnetic moment.

9. Explain the variation in E0M3+/M2+  3d series.

10. Write chemical equations for the reactions involved in the manufacture of potassium permanganate from pyrolusite ore.

11. (i) Name the transition metal
(a) Which is used in the manufacture of sulphuric add.
(b) That is used in Haber's process.
(c) That have light sensitive properties and act as valuable source in photo graphic industry.
(ii) Write the equations which are involved in the oxidation of hydrogen sulphide to sulphur by KMnO4 solution.

12. What are the uses of potassium dichromate?

13. In an octahedral crystal field, draw the figure to show splitting of d orbitals

14. Write the postulates of Werner’s theory

15. Calculate the number of atoms in a fcc unit cell

16. For a reaction x+y+z$\longrightarrow$ productsthe rate law is given by ratek =k[x]3/2[y]1/2 what is the overall order of the reaction and what is the order of the reaction with respect to z.

17. A gas phase reaction has energy of activation 200 kJ mol-1. If the frequency factor of the reaction is is 1.6 x1013s-1 Calculate the rate constant at 600 K.(e-40.09 = 3.8 x 10-48)

18. Explain common ion effect with an example

19. Calculate the extent of hydrolysis and the pH of 0.1 M ammonium acetate Given that $K_{a}=K_{b}=1.8\times10^{-5}$

20. 0.1M NaCl solution is placed in two different cells having cell constant 0.5 and 0.25cm-1 respectively. Which of the two will have greater value of specific conductance.

21. Addition of Alum purifies water. Why?

22. Writes the chemical equation for Williamson synthesis of 2-ethoxy – 2- methyl pentane  starting from ethanol and 2 – methyl pentan -2-ol

23. Account for the following
i. Aniline does not undergo Friedel – Crafts reaction
ii. Diazonium salts of aromatic amines are more stable than those of aliphatic amines
iii. pKb of aniline is more than that of methylamine
iv. Gabriel phthalimide synthesis is preferred for synthesising primary amines.
v. Ethylamine is soluble in water whereas aniline is not
vi. Amines are more basic than amides
vii. Although amino group is o – and p – directing in aromatic electrophilic substitution reactions, aniline on nitration gives a substantial amount of m – nitroaniline.

24. What are reducing and non – reducing sugars?

25. Write the structural formula of aspirin.