Board : Central Board Of Secondary Education
Exam : Class XII
Subject : Chemistrya
Document Type : Sample Paper
Website : cbse.nic.in
Download Model/Sample Question Paper : https://www.pdfquestion.in/uploads/cbse.nic.in/7037-chem-xii-3.pdf
Chemistry Sample Paper – III :
Class – XII :
Time : Three Hours
Max. Marks : 70
Related : Central Board Of Secondary Education Class XII Physics Paper Sample : www.pdfquestion.in/7035.html
General Instructions :
1. All questions are compulsory.
2. Question nos. 1 to 8 are very short answer questions and carry 1 mark each.
3. Question nos. 9 to 18 are short answer questions and carry 2 marks each.
4. Question nos. 19 to 27 are also short answer questions and carry 3 marks each.
5. Question nos. 28 to 30 are long answer questions and carry 5 marks each.
6. Use log tables if necessary, use of calculators is not allowed.
1. Name the type of point defect that occurs in a crystal of zinc sulphide. 1
3. Give the IUPAC name of the following compound 1
4. How many octahedral voids are there in l mole of a compound having cubic close packed structure? 1
5. What is the molecularity of the reaction? 1
6. In each of the following pairs of organic compounds, identify the compound which will undergo SN1 reaction faster? 1
7. In the ring test for identification of nitrate ion, what is the formula of the compound responsible for the brown ring formed at the interface of two liquids? 1
8. Except for vitamin B12, all other vitamins of group B, should be supplied regularly in diet. Why? 1
9. An element E crystallizes in body centred cubic structure. If the edge length of the cell is 1.469 x 10–10 m and the density is 19.3 g cm-3, calculate the atomic mass of this element. Also calculate the radius of an atom of this element. 2
10. The following curve is obtained when molar conductivity (y-axis) is plotted against the square root of concentration
(x – axis) for two electrolytes A and B.
(a) What can you say about the nature of the two electrolytes A and B?
(b) How do you account for the increase in molar conductivity ?mfor the electrolytes A and B on dilution? 2
11 (a) Adsorption of a gas on the surface of solid is generally accompanied by a decrease in entropy. Still it is a spontaneaons process. Explain.
(b) How does an increase in temperature affect both physical as well as chemical adsorption? 2
12. A colloidal solution of AgI is prepared by two different methods shown below
(i) What is the charge of AgI colloidal particles in the two test tubes (A) and (B)?
(ii) Give reasons for the origin of charge. 2
13. (a) What is the covalence of nitrogen in N2O5?
(b) Explain why both N and Bi do not form pentahalides while phosphorus does. 2
OR
When conc. H2SO4 was added into an unknown salt present in a test tube, a brown gas (A) was evolved. This gas intensified when copper turnings were also added into this test-tube. On cooling, the gas (A) changed into a colourless gas (B).
(a) Identify the gases A and B.
(b) Write the equations for the reactions involved.
14. Which is a stronger acid – Phenol or Cresol? Explain. 2
15. (a) How can you convert an amide into an amine having one carbon less – than the starting compound?
(b) Name the reaction.
(c) Give the IUPAC name and struclure of the amine obtained by the above method if the amide is chlorobut anamide.
16. (a) Why does chlorine water lose its yellow colour on standing?
(b) What happens when Cl2 reacts with cold dilute solution of sodium hydroxide? Write equation only. 2
18. Give mechanism of preparation of ethoxyethanle from ethanol. 2
19. (a) A current of 1.50 amp was passed through an electrolytic cell containing AgNO3 solution with inert electrodes.
The weight of Ag deposited was 1.50g. How long did the current flow?
(b) Write the reactions taking place at the anode and cathode in the above cell.
(c) Give reactions taking place at the two electrodoes if these are made up of Ag. 3
20. (i) Answer the following questions on the basis of the above curve for a first order reaction :-
(a) What is the relation between slope of this line and rate constant? (1)
(b) Calculate the rate constant of the above reaction if the slope is 2 x 10-4 S1
(ii) Derive the relationship between half life of a first order reaction and its rate constant. 3