Time: 1 Hour

 CHEMISTRY

 

Max.Marks : 50

Instructions:

(1) Answer must be written either in English or the medium of instruction of the candidate in high school.

(2) There will be no negative marking

(3) Use of calculators or graph papers is not permitted

(4) Answer all the questions. Each question carries 2 Marks.


1. What is the action of heat on following salts? Explain with balanced equations.

a) FeSO4 b) AgNO3

2. Sugar forms clear solution but soap forms cloudy solutions. Why?

3. What is the composition of baking powder? Explain how it bakes the bread to make it spongy? (with chemical equations)

4. When iron is exposed to atmosphere surface of the metal becomes brown but silver under similar conditions becomes black. Explain with equations?

5. BH3 acts as a Lewis acid whereas NH3 acts as Lewis base. Explain with proper structures?

6. Write the cathodic and anodic reactions when aqueous solution of KNO3 is electrolysed by using Pt electrodes.

7. What is electrolyte? What is the basic requirement for a substance to act as electrolyte?

8. In the given salt cation is called as basic radical and anion is called as acid radical. Why?

9. Why hydrogen peroxide acts as oxidising as well as reducing agent?

10. Hardness of IA-group elements gradually decreases down the group. Why?

11. What way thermochemical equations are more informative than skeletal and balanced chemical equations?

12. What are the simplest tests that are used for identification of purity of the chemical sample?

13. Total hardness of water cannot be removed by simple heating. Why?

14. CO2 and SiO2 are the oxides of elements of same group but CO2 is a gas but SiO2 is solid. Why?

                    15. All exothermic reactions are not spontaneous reactions. Why?

                    16. What are the internal factors that decide the physical state of the substance?

17. Aqueous solution of CuSO4 cannot be stored in Zn container but aqueous solution of ZnSO4 can be stored in Cu vessel. Why?

18. Match each of the chemical species in Column I with its property / properties given in corresponding Column II & Column III. No partial marking.

Column-I

Column-II

Column-III

a) BeH2

1. sp3d2

(i) trigonal planar

b) CH2BrCl

2. sp3

(ii) octahedral

c) PF6-

3. sp2

(iii) distorted tetrahedron

d) BF3

4. sp

(iv) linear

20. Indicate whether the following reaction is exothermic or endothermic by properly computing the given data:

Mg + 2Xg → M + 2X ;

IE1 of Mg = 737.7 Kj mol-1 ; IE2 of Mg = 1451 Kj mol-1 ; EA1 of Xg = -328 Kj mol-1