" /> -->

#### Important 3 Mark Book Back Questions (New Syllabus) 2020

12th Standard EM

Reg.No. :
•
•
•
•
•
•

Chemistry

Time : 01:00:00 Hrs
Total Marks : 72

Part A

24 x 3 = 72
1. Explain zone refining process with an example using the Ellingham diagram given below

2. Describe the structure of diborane

3. How will you prepare chlorine in the laboratory?

4. Give the uses of argon.

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

6. Explain why Cr2+ is strongly reducing while Mn3+ is strongly oxidizing.

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

8. Give the difference between double salts and coordination compounds.

9. Write short note on metal excess and metal deficiency defect with an example

10. What is the two dimensional coordination number of a molecule in square close packed layer?

11. Explain briefly the collision theory of bimolecular reactions

12. Explain pseudo first order reaction with an example

13. (ii) The half life of a first order reaction x ⇾products is 6.932 x 104 s at 500K. What percentage of x would be decomposed on heating at 500K for 100 min. (e0.06 = 1.06).

14. Calculate the pH of 1.5$\times$10-3Msolution of Ba(OH)2

15. Calculate the pH of 0.1M CH3COOH solution. Dissociation constant of acetic acid is $1.8\times10^{-5}$.

16. Why is AC current used instead of DC in measuring the electrolytic conductance?

17. Reduction potential of two metals M1 and M2 are $E^{0}_{M^{2+}_{1}|M_{1}} = -2.3V$ and $E^{0}_{M^{2+}_{1}|M_{1}} = 0.2V$ Predict which one is better for coating the surface of iron. Given: $E^{0}_{Fe^{2+}|Fe} = -0.44$V.

18. Why are lyophillic colloidal sols are more stable than lyophobilc colloidal sol.

19. Write the mechanism of acid catalysed dehydration of ethanol to give ethane.

20. Compound (A) C6H12O2 on reduction with LiAlH4 yields two compounds B and C. The compound (B) on oxidation gave (D) which on treatment with aqueous alkali and subsequent heating furnished E. The latter on catalytic hydrogenation gave (C). Compound (D) on oxidation gave monobasic acid (molecular formula weight = 60). Deduce the structure of (A), (B), (C), (D) and (E).

21. How will you convert benzaldehyde into the following compounds?
(i) benzophenone
(ii) benzoic acid
(iii) hydroxyphenylaceticacid.

22. Arrange the following
i. In increasing order of solubility in water, C6H5 NH2,(C2H5)2 NH,C2H5NH2
ii. In increasing order of basic strength
a) aniline, p- toludine and p – nitroaniline
b) C6H5 NH2,C6H5 NHCH3,C6H5NH2 ,p-Cl-C6- H4-NH2
iii. In decreasing order of basic strength in gas phase
(C2H5)NH2 ,(C2H5)NH, (C2H5)5N and NH3
iv. In increasing order of boiling point
C6H5OH, (CH3)2NH, C2H5NH2
v. In decreasing order of the pKb values
C2H5NH2, C6H5NHCH3.(C2H5) NH and CH3NH2
vi. Increasing order of basic strength
C2H5NH2,C6H5NH(CH3)2 ,(C2H5)2 NH and CH3NH2
vii. In decreasing order of basic strength

23. What are reducing and non – reducing sugars?

24. Explain the mechanism of cleansing action of soaps and detergents