Practice Paper-I

Practice Paper-I

Subject: Chemistry Marks:70

Grade: XII Time: 3 hrs.

General Instructions:

1. All questions are compulsory

2. Marks of each question are indicated against it.

3. Question numbers 1 to 8 are very short questions, each of 1 mark. Answer these in one word or about one sentence each.

4. Question numbers 9 to 18 are short answer questions of 2 marks each. Answer this in about 30 words each.

5. Question numbers 19 to 27 are short answer questions of 3 marks each. Answer these in about 40 words each.

6. Question numbers 28 to 30 are long answer questions of 5 marks each. Answer these in about 70 words.

7. Use log tables if necessary. Calculators are not permitted.

1. Write IUPAC name of the following compound

2. Propanol has higher boiling point than Butane. Why?

3. Lyophilic colloid is more stable than lyophobic colloid. Why?

4. Can we separate a mixture of 5% water and 95% ethanol by simple distillation? Justify your answer.

5. State Henry’s Law.

6. Write a reaction which confirms the presence of aldehyde group in Glucose.

7. What is peptide bond?

8. State any one condition under which a bimolecular reaction may be kinetically of the first order.

9. Give four structural differences between DNA and RNA.

10. Aluminium crystallizes in a cubic close packed structure. Its metallic radius is 125pm.

(a) What is the length of the side of the unit cell?

(b) How many unit cells are there in 1.00cm3 of Aluminium?

11. Explain the following with suitable example

(i) n- type semiconductor

(ii) F-centres

12. A first order reaction takes 40 min for 30% decomposition. Calculate t1/2.

13. The decomposition of hydrocarbon follows the equation
k = (4.5 × 1011s–1) e-28000K/T
Calculate energy of activation (Ea).

14. Aryl halides are less reactive than alkyl halides towards nucleophillic substitution reactions. Why?

15. Write the mechanism of the following reaction:

16. Write short notes on
(i) Hoffmann bromamide degradation reaction
(ii) Cannizzaro Reaction

17. Give a chemical test to distinguish between the following
(a) Ethyl amine and Diethyl amine

(b) Acetaldehyde and Benzaldehyde

18. (a) Calculate the magnetic moment of a divalent ion in aqueous solution if its atomic number is 25.
(b )Compare the chemistry of the actinoids with that of lanthanoids with reference to: (i) electronic configuration (ii) oxidation states and

What is Lanthanoid contraction? Write its cause and consequences?

19. (i) Give reason of the followings

(a) Phenyl methyl ether (or anisole) reacts with HI to give phenol and methyl iodide and not iodobenzene and methyl alcohol.

(b) Phenols are more acidic than alcohols.

(ii) Name the reagent used in the oxidation of primary alcohol to aldehyde.

20. A 5% solution (by mass) of cane sugar in water has freezing point of 271K. Calculate the freezing point of 5% glucose in water if freezing point of pure water is 273.15 K.

21. Explain the following terms:

(i) Electrophoresis

(ii) Peptization

(iii) Shape selective catalysis?

22. Give reason for the following observation
(i) Cu2+ ion is more stable than Cu+ in aqueous solution
(ii) Cr has maximum melting point in 3d series.
(iii) Transition metals and their many compounds act as good catalyst.

(i) Indicate the steps for the preparation of KMnO4 from pyrolusite ore.

(ii) Write the ionic equations when potassium permanganate reacts with oxalic acid.

23. (a) What is the role of cryolite in the metallurgy of aluminium?
(b) The value of ΔfG0 for formation of Cr2O3 is – 540 kJmol−1and that of Al2O3 is
– 827 kJmol−1. Is the reduction of Cr2O3 possible with Al?

24. Give reasons:

(i) Hypo phosphorous acid is good reducing agent.

(ii) H2S is less acidic than H2Te. Why?

(iii) Chlorine water acts as a bleaching agent.

25. a) Write the IUPAC name for [Co(en)3]2(SO4)3
(b) How many geometrical isomers are possible in the coordination entity [Co (NH3)3(NO3)3]?
(c) Give the number of unpaired electrons in [Ni(CN)4]-2. (Atomic no of Ni = 27)

26. (a) Why do soaps not work in hard water?
(b) What are the main constituents of dettol?

27. a) Name the monomers of biodegradable polymer PHBV.
(b) Why the numbers 66 and 6 put in the name of nylon -66 and nylon -6?
(c) How vulcanization changes the properties of natural rubber?

28. (a) How will you bring about the following conversions

(1) Propanone to Propene

(2) Benzoic acid to Benzaldehyde

(3) Ethanal to 3-Hydroxybutanal

(b) Complete the following reactions:-

(i)

(ii)

(a) An organic compound with the molecular formula C9H10O forms 2,4-DNP derivative, reduces Tollens’ reagent and undergoes Cannizzaro reaction. On vigorous oxidation, it gives 1,2-benzenedicarboxylic acid. Identify the compound and give the chemical reactions involved.

(b) Predict the products formed when cyclohexanecarbaldehyde reacts with following reagents.

(i) PhMgBr and then H3O+

(ii) Zinc amalgam and dilute hydrochloric acid

29. (i) Account for the following:

(a) Nitrogen exists as diatomic molecule and phosphorus as P4. Why

(b) Bond dissociation energy of F2 is smaller than Cl2. Why?

(d) Noble gases have low boiling point.

(ii) Draw the structure of XeO3.

(a) Write balanced equations for the following:

(i) White phosphorus is heated with concentrated NaOH solution in an inert atmosphere of CO2.

(ii) The reaction of Cl2 with hot and concentrated NaOH.

(iii) The reaction of platinum with aqua-regia

(b) Write the chemical equations involved in Brown ring test for nitrate ion.

30. (a) Resistance of a conductivity cell filled with 0.1 mol L–1 KCl solution is 100 Ω. If the resistance of the same cell when filled with 0.02 mol L–1 KCl solution is 520 Ω, calculate the conductivity and molar conductivity of 0.02 mol L–1 KCl solution. The conductivity of 0.1 mol L–1 KCl solution is 1.29 S/m.

(b) Write the cathodic and anodic reactions for the charging of lead storage battery.

(a) Write the equations involved at anode and cathode in rusting of Iron.

(b) Calculate the equilibrium constant for the reaction:
Zn(s) + Cu+2(aq) Zn+2(aq) + Cu(s),
Given: EoZn+2/Zn = - 0.76V and Eo Cu+2/Cu = + 0.34V.

Practice Paper-II

Subject: Chemistry Marks:70

Grade: XII Time: 3 hrs.

Gereral instructions;-

1. All Questions are compulsory.

2. Q. No. 1-8 carry 1 marks each.

3. Q. No. 9-18 carry 2 marks each

4. Q. No. 19-27 carry 3 marks each.

5. Q. No. 28-30 carry 5marks each.

6. Use of Log-Table is allowed.

7. Use of calculator is not allowed.

1 / What is no. of atoms per unit cell in a body centred cubic structure? / 1
2 / A cubic solid is made up of two elements X and Y. Atoms Y are at the corners of the cube and X at body centre. What is formula of compound? / 1
3 / A reaction is 50% complete in 2 hours and 75 % complete in 4 hours. What is order of reaction? / 1
4 / The rate of reaction X--à Y become 8 times when the concentration of reactant is doubled. Write the rate law for reaction. / 1
5 / Name one poisonous gas which can be prepared from chlorine gas. / 1
6 / Write common name for 2-Chloro-2-methylpropane. / 1
7 / What type of aldehyde undergoes cannizaro’s reaction? / 1
8 / What is name given to linkage that holds two monosaccharide units together? / 1
9 / An element crystallizes in FCC structure; 200 g of this element has 2.408 x 10 24atoms. If the density of A is 7.2 g per cc, calculate the edge length of unit cell. / 2
10 / Give reason
a) Rusting of iron is faster in saline water than in ordinary water.
b) Aluminium metal cannot be produced by electrolysis of aq. solution of aluminium salt. / 2
11 / What is de-emulsification? How it is brought about? / 2
12 / What happens when:
a) A beam of light is passed through arsenic sulphide sol.
b) KCl is added to Fe (OH)3 sol. / 2
13 / Are all bonds of PCl 5 are equal? Justify your answer. / 2
14 / Compare the basic strength of NH 3 and PH 3 giving reason. / 2
15 / Which is more acidic ethanol or phenol? Give reason. / 2
16 / Write short notes on:
a) Williamson’s synthesis
b) Reimer Tiemann reaction. / 2
17 / Give reasons
i) pKb value of aniline is higher than that of methylamine. Explain.
ii) Aniline does not undergo Friedel craft reactions. / 2
18 / Convert
i) Nitrobenzene into toluene.
ii) Aniline into benzylamine / 2
19 / A current of 3.7 Ampere is passed for 6 hours between Pt electrodes in 500 ml of a 2 M solution of Ni (NO3)2 . What will be the molarity of solution at the end of electrolysis? / 3
20 / a) Write units for rate constant for a reaction of 2nd order.
b) Show that in case of 1st order reaction, the time required for 99 % completion is double than that required for 90 % completion. / 1
2
21 / a) Describe role of depressant on froth floatation.
b) Explain a Mond’s process. / 3
22 / i) Why N cannot show valency of 5 like Phosphorus present in same group.
ii) Why Xe form compound only with oxygen or Flourine only.
iii) Why H2O exist as liquid while H2S exist as gas? / 1
1
1
23 / Show that [Ni(CN)4]2- is square planner and [Ni Cl4]2- is tetrahedral with help of valence bond theory. / 3
24 / i) Write the order of reactivity of 4 different isomers of butyl chloride by SN1 mechanism. Give reason.
ii) What is ambident nucleophile? Give example. / 2
1
25 / Name 2 components of starch and compare them. / 3
26 / i) What are main purposes for vulcanization of rubber?
ii) What are differences between thermosetting polymers and thermoplastic polymers? / 1
2
27 / Explain the terms with suitable examples
i) Cationic detergent
ii) Biodegradable detergent
iii) Analgesic. / 1
1
1
28 / i) Calculate the vapour pressure of a solution at 373 K containing 3 g of cane sugar in 33 g of water.
ii) Explain the reason for positive deviation of solutions with example.
iii) What happens when blood cell is placed in 0.8% NaCl(aq) solution?
OR
i) 0.85 % aq solution of NaNO3 is apparently 90% dissociated at 27 0 C. Calculate its osmotic pressure. (density of solution = 1 g/ml)
ii) Prove that osmotic pressure is colligative property.
iii) Define Molality. / 2
2
1
2
2
1
29 / i) Describe the preparation of Potassium dichromate from chromite ore.
ii)Write its balanced reaction with
a) Iron (II) solution
b) Iodide ions
OR
i) What is the effect of pH on the solution of Potassium dichromate?
ii) Why transition metals form no. of alloys?
iii) Zn, Hg and Cd are not considered transition metals Why?
iv) Why Sc cannot show oxidation state of +2?
v) Why Transition metals have high enthalpy of atomization? / 3
1
1
1
1
1
1
1
30 / i) Give chemical test to distinguish between
a) formaldehyde and acetaldehyde
b) methanoic acid and ethanoic acid
ii) An organic compound A with molecular formula C8H8O form an orange red ppt. with 2,4-DNP reagent and gives Yellow ppt on heating with iodine in presence of NaOH. It neither reduces Tollen’s reagent nor Fehling solution. It does not decolorize bromine water. On drastic oxidation with chromic acid, it gives a carboxylic acid B having formula C7H6O2 Identify the compounds A, B and explain the reactions involved.
OR
i) Give mechanism for addition of HCN on carbonyl group.
ii) Draw the structure of semicarbazone of heaxan-3-one.
iii) What happens when sodium benzoate is heated with soda lime
iv) Give chemical test to distinguish between
a) Phenol and benzoic acid
b) Acetophenone and Benzophenone. / 1
1
3
1
1
1
1
1

Practice Paper-III

Subject: Chemistry Marks:70

Grade: XII Time: 3 hrs.

GENERAL INSTRUCTIONS:

(i) All questions are compulsory.

(ii) Marks for each question are indicated against it.

(iii) Questions no.1to 8 is very short answer questions and carries 1 marks each.

(iv) Questions no.9to 18 is short answer questions and carries 2 marks each.

(v) Questions no. 19to 27 are also short answer question and carry 3 marks each.

(vi) Questions no.28to30 is long- answer question and carries 5 marks each.

(vii) Use long Tables, if necessary. Use of calculators is not allowed.

Q.1-Why common salt is sometimes yellow instead of being pure white? 1

Q.2-Why is it advised to add ethylene glycol to water in a car radiator while driving in a hill station? 1

Q.3-What is the role of desorption in the process of catalysis? 1

Q.4-What is the significance of leaching in the extraction of aluminum? 1

Q.5- Bond angle in PH+4 is higher than in PH3? 1

Q.6-What is the basicity of H3 PO4? 1

Q.7- Write structures of the compound: 1-Bromo-4-sec.butyl-2-methylbenzenene. 1

Q.8- Name the aldehyde which does not give Fehling’s solution test. 1

Q.9-What role does the molecular interaction play in the solution of alcohol and water? 2

Q.10- The combustion of a hydrocarbon follows the equation;

k= (4.5x 1011 s_1) e_ (28000k)/T. Calculate Ea. 2

Q.11- Calculate the mass% of aspirin (C9H8O4) in acetonitrile (CH3CN) when 6.5 of C9H8O4 Is dissolved in 450g of CH3CN. 2

Q.12- Describe the method of refining of nickel. 2

Q.13- Write the mechanism of acidic dehydration of ethanol to ethene. 2

Q.14- Arrange the fallowing set of compounds in order of increasing boiling points:2

(a) pentan-1-ol, butane-1-ol, butane-2-ol, ethanol, propan-1-ol.

(b) pentan1-ol, butane, pentanal, ethoxyethane