CLASS - XII
TIME: 3 Hrs. SUBJECT- Chemistry M.M.:-70
General Instructions:
1. All questions are compulsory.
2. Questions no. 1 to 8 are very short answer questions and carry 1 mark each.
3. Questions no. 9 to 18 are short answer questions and carry 2 marks each.
4. Questions no. 19 to 27 are also short answer questions and carry 3 marks each.
5. Questions no. 28 to 30 are long answer questions and carry 5 marks each.
6. Use log tables if necessary, use of calculators is not allowed.
Values of Logarithms: Log 4 = 0.6020
1. A compound is formed by two elements M and N. The element N forms ccp and atoms of M occupy
1/3rdtetrahedral voids. What is the formula of the compound?
2. At the same temperature Hydrogen is more soluble in water than Helium. Which of the two has
higher KH value?
3. What is Faraday’s second law of electrolysis.
4. For a reaction, A + B ----- Products, the rate law is given by r = k[A]1/2[B]2. What is the
order of the reaction?
5. What is chemisorption?
6. Between C and CO, which one is better reducing agent after 983K.
7. Why +5 state of Bi is less stable than +5 state of Sb?
8. What is co ordination entity?
9. (i) The reaction 2H2(g) + O2(g) → 2H2O is thermodynamically feasible. How is it that a
Mixture of H2 and O2kept at room temperature has no tendency to form water?
(ii) Identify the reaction order if the unit of the rate constant is sec-1.
10. State what are:
(i) Henry’s law?
(ii) Relative lowering of vapour pressure?
11. Calculate the freezing point of a one molar aqueous solution of KCl.
[Density of the solution = 1.04 g/cc., Kf = 1.86 K kg mol-1, At wt. of K = 39 and Cl = 35.5]
12. State:
(a) One limitation of Ellingham diagram.
(b) A chemical equation illustrating van-Arkel method.
13. Define the following terms (i) Ferromagnetism (ii) F center
14. What is semiconductor? Describe the two main types of semiconductors.
15. The specific conductance of 0.05 N solution of an electrolyte at 298 K is 0.02 Scm-1. Calculate the
equivalent conductance.
16. pin magnetic moment of B
17. (i) Write the IUPAC name of the following Compound
NH4[Cr(NH3)2(SCN)4]
(ii) Write the formula of the following compound
Dichloridobis(ethane-1,2-diamine)platinum(IV) nitrate
18. For the complex [Fe(en)2Cl2]Cl, identify (a) the number of geometrical isomers (b) whether there is an optical
isomer. If yes draw structure
19. calculate the density of silver which crystallizes in fcc form. The distance between nearest metal atom is 287
pm ( molar mass of Ag = 107.87 gmol-1; No = 6.022×1023)
20. Determine the osmotic pressure of a solution prepared by dissolving 25 mg of K2SO4 in 2 litre of water at 25oC,
assuming that it is completely dissociated.
21. How will you classify the colloids on the basis of molecular size? Distinguish between multimolecular and
macromolecular colloids with the help of example.
22. Explain the following terms (i) Tyndall effect (ii) Gold number (iii) Peptization
23. Write the chemical reactions which take place in different zones in blast furnace during the extraction of iron.
24. State why:
(a) Bleaching of flowers by Cl2 is permanent while that by SO2 is temporary.
(b) Enthalpy of dissociation of F2 is much less than that for Cl2.
(c) Nitric oxide becomes brown when released in air.
25. Draw the structures and write basicity of:
(i) Marshall’s acid (ii) Pyrophosphoric acid (iii) Sulphurous acid
26. Explain the followings
(i) Variation of acidic strength of halogen acids of a particular halogen in different oxidation states.
(ii) Reaction condition used to maximize the yield in Haber process.
27. (i) Write chemical reaction involving in preparation of KMnO4 from pyrolusite.
(ii) At 300 K H2O is liquid while H2S is gas. Why?
28. (a) State two consequences of lanthanide contraction. 2
(b) Account for the following: 1×3
(i) Vanadium pentoxide acts as a catalyst?
(ii) In any transition series with increase in atomic number, the atomic radius does not change very much.
(iii) f-Block elements are called inner-transition elements.
OR
(a) Complete the following:
(i) Cr2O72- + 14H+ + 6e- → ………….. + 7H2O 2
(ii) CrO42- + …………. ……………. ………….. + 4OH-
(b) Account for the following: 1×3
(i) Size of trivalent cations in the lanthanoid series decreases with increasing atomic number.
(ii) Transition metal fluorides are ionic whereas chlorides and bromides are usually covalent.
(iii) Chemistry of lanthanoids is quite similar.
29. (a) Write down the reactions involved in the working of a H2–O2 fuel cell. 2
(b) A solution of Ni (NO3)2 is electrolysed between platinum electrodes using a current of 5.0 amperes for
20.0 minutes. What mass of Ni is deposited at the cathode? [At. Wt. Ni = 58.7] 3
OR
(a) (i) State Kohlrausch’s law. 1×2
(ii) Why does an alkaline medium inhibit the rusting of iron?
(b) Calculate the equilibrium constant for the following reaction: 3
Zn(s) + Cu2+(aq) Zn2+(aq) + Cu(s)
[ E0Zn2+/Zn = – 0.763 V and E0ZCu2+/Cu = + 0.34 V ]
30. For a chemical reaction variation in concentration, ln[R] vs time(min) plot is shown below:
i) What is the order of the reaction? 1×5
ii) What are units of rate constant k for the reaction?
iii) If initial concentration of the reactant is half of the original concentration how will t1/2 change?
iv) Draw the plot of log[Ro]/[R] vs time(s).
v) What will be the plot of half life vs [Ro] of the reaction?
Or
i) What is the difference between order of reaction and molecularity? 2
ii) The rate of reaction quadruples when the temperature changes from 293 K to 313 K. calculate the energy of
activation of the reaction assuming that it does not change with temperature. 3
TIME: 3 Hrs. SUBJECT- Chemistry M.M.:-70
General Instructions:
1. All questions are compulsory.
2. Questions no. 1 to 8 are very short answer questions and carry 1 mark each.
3. Questions no. 9 to 18 are short answer questions and carry 2 marks each.
4. Questions no. 19 to 27 are also short answer questions and carry 3 marks each.
5. Questions no. 28 to 30 are long answer questions and carry 5 marks each.
6. Use log tables if necessary, use of calculators is not allowed.
Values of Logarithms: Log 4 = 0.6020
1. A compound is formed by two elements M and N. The element N forms ccp and atoms of M occupy
1/3rdtetrahedral voids. What is the formula of the compound?
2. At the same temperature Hydrogen is more soluble in water than Helium. Which of the two has
higher KH value?
3. What is Faraday’s second law of electrolysis.
4. For a reaction, A + B ----- Products, the rate law is given by r = k[A]1/2[B]2. What is the
order of the reaction?
5. What is chemisorption?
6. Between C and CO, which one is better reducing agent after 983K.
7. Why +5 state of Bi is less stable than +5 state of Sb?
8. What is co ordination entity?
9. (i) The reaction 2H2(g) + O2(g) → 2H2O is thermodynamically feasible. How is it that a
Mixture of H2 and O2kept at room temperature has no tendency to form water?
(ii) Identify the reaction order if the unit of the rate constant is sec-1.
10. State what are:
(i) Henry’s law?
(ii) Relative lowering of vapour pressure?
11. Calculate the freezing point of a one molar aqueous solution of KCl.
[Density of the solution = 1.04 g/cc., Kf = 1.86 K kg mol-1, At wt. of K = 39 and Cl = 35.5]
12. State:
(a) One limitation of Ellingham diagram.
(b) A chemical equation illustrating van-Arkel method.
13. Define the following terms (i) Ferromagnetism (ii) F center
14. What is semiconductor? Describe the two main types of semiconductors.
15. The specific conductance of 0.05 N solution of an electrolyte at 298 K is 0.02 Scm-1. Calculate the
equivalent conductance.
16. pin magnetic moment of B
17. (i) Write the IUPAC name of the following Compound
NH4[Cr(NH3)2(SCN)4]
(ii) Write the formula of the following compound
Dichloridobis(ethane-1,2-diamine)platinum(IV) nitrate
18. For the complex [Fe(en)2Cl2]Cl, identify (a) the number of geometrical isomers (b) whether there is an optical
isomer. If yes draw structure
19. calculate the density of silver which crystallizes in fcc form. The distance between nearest metal atom is 287
pm ( molar mass of Ag = 107.87 gmol-1; No = 6.022×1023)
20. Determine the osmotic pressure of a solution prepared by dissolving 25 mg of K2SO4 in 2 litre of water at 25oC,
assuming that it is completely dissociated.
21. How will you classify the colloids on the basis of molecular size? Distinguish between multimolecular and
macromolecular colloids with the help of example.
22. Explain the following terms (i) Tyndall effect (ii) Gold number (iii) Peptization
23. Write the chemical reactions which take place in different zones in blast furnace during the extraction of iron.
24. State why:
(a) Bleaching of flowers by Cl2 is permanent while that by SO2 is temporary.
(b) Enthalpy of dissociation of F2 is much less than that for Cl2.
(c) Nitric oxide becomes brown when released in air.
25. Draw the structures and write basicity of:
(i) Marshall’s acid (ii) Pyrophosphoric acid (iii) Sulphurous acid
26. Explain the followings
(i) Variation of acidic strength of halogen acids of a particular halogen in different oxidation states.
(ii) Reaction condition used to maximize the yield in Haber process.
27. (i) Write chemical reaction involving in preparation of KMnO4 from pyrolusite.
(ii) At 300 K H2O is liquid while H2S is gas. Why?
28. (a) State two consequences of lanthanide contraction. 2
(b) Account for the following: 1×3
(i) Vanadium pentoxide acts as a catalyst?
(ii) In any transition series with increase in atomic number, the atomic radius does not change very much.
(iii) f-Block elements are called inner-transition elements.
OR
(a) Complete the following:
(i) Cr2O72- + 14H+ + 6e- → ………….. + 7H2O 2
(ii) CrO42- + …………. ……………. ………….. + 4OH-
(b) Account for the following: 1×3
(i) Size of trivalent cations in the lanthanoid series decreases with increasing atomic number.
(ii) Transition metal fluorides are ionic whereas chlorides and bromides are usually covalent.
(iii) Chemistry of lanthanoids is quite similar.
29. (a) Write down the reactions involved in the working of a H2–O2 fuel cell. 2
(b) A solution of Ni (NO3)2 is electrolysed between platinum electrodes using a current of 5.0 amperes for
20.0 minutes. What mass of Ni is deposited at the cathode? [At. Wt. Ni = 58.7] 3
OR
(a) (i) State Kohlrausch’s law. 1×2
(ii) Why does an alkaline medium inhibit the rusting of iron?
(b) Calculate the equilibrium constant for the following reaction: 3
Zn(s) + Cu2+(aq) Zn2+(aq) + Cu(s)
[ E0Zn2+/Zn = – 0.763 V and E0ZCu2+/Cu = + 0.34 V ]
30. For a chemical reaction variation in concentration, ln[R] vs time(min) plot is shown below:
i) What is the order of the reaction? 1×5
ii) What are units of rate constant k for the reaction?
iii) If initial concentration of the reactant is half of the original concentration how will t1/2 change?
iv) Draw the plot of log[Ro]/[R] vs time(s).
v) What will be the plot of half life vs [Ro] of the reaction?
Or
i) What is the difference between order of reaction and molecularity? 2
ii) The rate of reaction quadruples when the temperature changes from 293 K to 313 K. calculate the energy of
activation of the reaction assuming that it does not change with temperature. 3
