This year, CBSE class 12 Chemistry paper is scheduled to be held on March 25th. Thus, with only a few days left for the exam, students appearing for the exam must gear up for the final revisions. They should start solving more and more previous years’ question papers which will help the students track their performance and understand the exam pattern along with latest marking trends. Moreover, it will give a clear overview of the types of questions asked in the board exam.
Jagranjosh here brings a collection of Class 12 Chemistry Last 5+1 years’ Short Answer Type Questions-II to help the students get a firm grip over the 3 marks questions that are probably going to be asked in the upcoming board exam.
As per the latest exam pattern in CBSE Class 12 Chemistry paper questions number 11 to 22 are short answer question that carry 3 marks each.
1. Silver crystallizes in face-centered cubic unit cell. Each side of this unit cell has a length of 400 pm. Calculate the radius of the silver atom. (Assume the atoms just touch each other on the diagonal across the face of the unit cell. That is each face atom is touching the four corner atoms.)
2. Nitrogen pentoxide decomposes according to equation
2N2O5 (g) → 4NO2 (g) + O2 (g)
This first order reaction was allowed to proceed at 40 °C and the data below were collected:
(a) Calculate the rate constant. Include units with your answer.
(b) What wil1 he the concentration of N2O5 after 100 minutes?
(c) Calculate the initial rate of reaction.
3. Explain how the phenomenon of adsorption finds application in each of the following process:
(i) Production of vacuum
(ii) Heterogeneous catalysis
(iii) Froth Floatation process
Define each of the following terms:
4. Describe the principle behind each of the following processes:
(i) Vapour phase refining of a metal.
(ii) Electrolytic refining of a metal.
(iii) Recovery of silver after silver ore was leached with NaCN.
5. Complete the following chemical equations:
6. Write the name, stereochemistry and magnetic behaviour of the following:
(At.nos. Mn = 25, Co = 27, Ni = 28)
7. Answer the following:
(a) Haloalkanes easily dissolve in organic solvents, why?
(b) What is known as a racemic mixture? Give an example.
(c) Of the two bromoderivatives, C6H5CH (CH3) Br and C6H5CH (C6H5) Br, which one is more reactive in SN1 substitution reaction and why?
8. (a) Explain why an alkylamine is more basic than ammonia.
(b) How would you convert
(i) Aniline to nitrobenzene
(ii) Aniline to iodobenzene?
9. Describe the following giving one example for each
(ii) Food preservatives
10. Copper crystallises with face centred cubic unit cell. If the radius of copper atom is 127.8 pm, calculate the density of copper metal. (Atomic mass of Cu = 63.55 u and Avogadro’s number, NA = 6.02 × 1023 mol-1)
Iron has a body centred cubic unit cell with the cell dimension of 286.65 pm. Density of iron is 7.87 g/cm3. Use this information to calculate Avogadro's number. (Atomic mass of Fe = 56.0 u)
11. The electrical resistance of a column of 0.05 M NaOH solution of diameter 1 cm and length 50 cm is 5.55 × 103 ohm. Calculate its resistivity, conductivity and molar conductivity.
12. The reaction, N2 (g) + O2 (g) → 2NO (g) contributes to air pollution whenever a fuel is burnt in air at a high temperature. At 1500 K, equilibrium constant K for it is 1.0 × 10-6. Suppose in a case [N2] = 0.80 mol L-1, and [O2] = 0.20 mol L-1, before any reaction occurs. Calculate the equilibrium concentrations of the reactants and the product after the mixture has been heated to 1500 K.
13. Explain the following terms giving a suitable example for each:
14. How would you account for the following:
(i) Among lanthanoids, Ln (III) compounds are predominant. However, occasionally in solutions or in solid compounds, +2 and +4 ions are also obtained.
(ii) The E0M2+/M for copper is positive (0.34 V), Copper is the only metal in the first series of transition elements showing this behaviour.
(iii) The metallic radii of the third (5d) series of transition metals are nearly the same as those of the corresponding members of the second series.
15. Name the following coordination entities and draw the structures of their stereoisomer:
(i) [Co(en)2Cl2]+ (en = ethan-1, 2-diamine)
(Atomic numbers Cr = 24, Co = 27)
16. Answer the following questions:
(i) what is meant by Chirality of a compound? Give an example.
(ii) Which one of the following compounds is more easily hydrolyzed by KOH and why?
CH3CHClCH2CH3 or CH3CH2CH2Cl
(iii) Which one undergoes SN2 substitution reaction faster and why?
CH3CH2CH2CH2CH2I Or CH3CH2CH2CH2CH2Cl
17. What is essentially the difference between alpha-glucose and beta-glucose? What is meant by pyranose structure of glucose?
18. Differentiate between thermoplastic and thermosetting polymers. Give one example of each.
19. The rate of a reaction becomes four times when the temperature changes from 293 K to 313 K. Calculate the energy of activation (Ea) of the reaction assuming that it does not change with temperature.
[R = 8.314 J/K mol, log 4 = 0.6021
20. What are the characteristics of the following colloids? Give one example of each.
(i) Multimolecular colloids
(ii) Lyophobic sols
21 Give reasons for the following:
(i) When R is an alkyl group R3P = 0 exists but R3N doesn’t.
(ii) PbCl4 is more covalent than PbCl2.
(iii) At room temperature, N2 is much less reactive.
22 For the complex [NiCl4]2-, write
(i) the IUPAC name
(ii) the hybridization type
(iii) the shape of the complex
(Atomic no. of Ni = 28)
What is meant by crystal field splitting energy? On the basis of crystal field theory, write the electronic configuration or d4 in terms of t2g and eg in an octahedral field when
(i) Δo > P
(ii) Δo < P
23. Give reasons for the following:
(i) Ethyl iodide undergoes SN2 reaction faster than ethyl bromide.
(ii) (±) 2-Butanol is optically inactive.
(iii) C− X bond length in halobenzene is smaller than C−X bond length in
CH3 − X.
24. Complete the following reactions:
25. (i)What class of drug is Ranitidine?
(ii) If water contains dissolved Ca2+ ions, out of soaps and synthetic detergents, which will you use for cleaning clothes?
(iii) Which of the following is an antiseptic?
0.2y phenol, 1% phenol
26. Calculate the emf of the following cell at 25°C:
Ag (s) | Ag+ (10-3M) || Cu2+ (10-1M) | Cu (s)
Given E0 cell = +0.46 V & log10n = n.
27. Shanti, a domestic helper of Mrs. Anuradha, fainted while mopping the floor. Mrs. Anuradha immediately took her to the nearby hospital where she was diagnosed to be severely ‘anaemic’. The doctor prescribed an iron rich diet and multivitamins supplement to her. Mrs. Anuradha supported her financially to get the medicines. After a month, Shanti was diagnosed to be normal.
(i) What values are displayed by Mrs. Anuradha?
(ii) Name the vitamin whose deficiency causes ‘pernicious anaemia'.
(iii) Give an example of a water soluble vitamin.
28. Calculate ΔrG0 for the following reactions:
Mg(s) + Cu2+ (aq) → Mg2+ (aq) + Cu (s)
Given, +2.71 V, 1F=96500C/mol
(b) Name the type of cell which was used in Apollo space programme for providing electrical power.
29. The following data were obtained during the first order thermal decomposition of SO2Cl2 at a constant volume:
Calculate the rate constant.
(Given: log4 = 0.6021, log2 = 0.3010)
30. What are emulsions? What e their different types? Give one example of each type.
31. Give reasons for the following:
(i) (CH3)3P = O exists but (CH3)3N = O does not.
(ii) Oxygen has less electron gain enthalpy with negative sign than sulphur.
(iii) H3PO2 is a stronger reducing agent than H3PO3.
32. (i) Write the IUPAC name of the complex [Cr(NH3)4Cl2]Cl
(ii) What type of isomerism is exhibited by the complex [Co(en)3]3+? (en = ethane-1,2-diamine)
(iii) Why is [NiCI4]2- paramagnetic but [Ni (CO)4] is diamagnetic? (Atomic no. Cr = 24, Co = 27, Ni = 28)
33. (a) Draw the structures of major mono halo products in each of the following reactions:
(b) Which halogen compound in each of the following pairs will react faster in SN2 reaction?
(i) CH3Br Or CH3I
(ii) (CH3)3C-Cl Or CH3-Cl
34. Account for the following:
(i) Primary amines (R-NH2) have higher boiling point than tertiary amines (R3N).
(ii) Aniline does not undergo Friedel-Crafts reactions:
(iii) (CH3)2NH is more basic than (CH3)3N in an aqueous solution.
Give the structures of A, B and C in the following reactions:
35. Define the following terms as related to proteins:
(i) Peptide linkage
(ii) Primary structure
36. On the occasion of world Health Day, Dr. Satpal organized a 'health camp’ for the poor farmers living in a nearby village. After check-up, he was shocked to see that most of the farmers suffered from cancer due to regular exposure to pesticides and many were diabetic. They distributed free medicines to them. Dr. Satpal immediately reported the matter to the National Human Rights Commission (NHRC). On the suggestions of NHRC, the government decided to provide medical care, financial assistance, setting up of super-speciality hospitals for treatment and prevention of the deadly disease in the affected villages all over India.
(i) Write the values shown by
(a) Dr. Satpal
(ii) What types of analgesics are chiefly used for the relief of pains of terminal cancer?
(iii) Give an example of artificial sweetener that could have been recommended to diabetic patients.
37. (i) Name the method used for the refining of Zirconium.
(ii) What is the role of CO in extraction of Iron?
(iii) Reduction of metal oxide to metal becomes easier if the metal is in liquid state. Why?
38. (a) How would you account for following
(i) The chemistry of actinoids is more complicated as compared to lanthanoids .
(ii) Transition metals form complex compounds
(b) Complete the following equation:
2MnO4- + 6H+ +5SO3 2-→
39. (i) Draw the geometrical isomers of complex [Co(en)2Cl2]+
(ii) On the basis of crystal field theory, write the electronic configuration for d4 ion Δ0 ˃ P
(iii) [NiCl4]2- is paramagnetic while Ni(CO)4 is diamagnetic though both are tetrahedral . Why? (Atomic no. Ni =28)
40. Predict the products of following reactions:
41. Write the name and structure of the monomer of following polymers.
42. (i) Which one of the following is polysaccharides:
Starch, maltose, Fructose, glucose
(ii)What is difference between native protein and denatured protein?
(iii)Write the name of the vitamin responsible for coagulation of blood.
43. Calculate the amount of CaCl2 (molar mass 111 g mol-1) which must be added to 500 g of water to lower its freezing point by 2K, assuming CaCl2 is completely dissociated.(Kf for water= 1.86 K kg mol-1)
44. An element with density 10 g cm-3 forms a cubic unit cell with edge length of 3 ×10-8 cm. What is the nature of cubic unit cell if the atomic mass of the element is 81 g mol-1?
45. How do you convert the following:
(i) Prop-1-ene to 1-fluoropropane
(ii) Chlorobenzene to 2-chlorotoluene
(iii) Ethanol to propanenitrile
Write the main products when
(i)n-butyl chloride is treated with alcoholic KOH
(ii) 2,4,6-trinitrochlorobenzene is subjected to hydrolysis.
(iii) Methyl chloride is treated with AgCN.
46. Give reasons for the followings:
(i) O-nitrophenol is more acidic than O-methoxy phenol
(ii) Butan-1-ol has a higher boiling point than diethyl ether.
(iii) (CH3)3C-O-CH3 on reaction with HI gives (CH3)3-I and CH3OH as main product and not (CH3)3-OH and CH3-I.
47. Calculate the emf of the following cell at 25°C;
Sn|Sn 2+(0.001M) || H+(0.01M) | H2(g)(1 bar) |Pt(s)
E0 Sn|Sn 2+ = -0.14 V E0 H+|H2 = 0.00 V
48. Give the reason for the following observations:
(i) Physisorption decreases with increase in temperature.
(ii) Addition of Alum purifies the water.
(iii) Brownian movement provides stability to the colloidal solution.
49. Write the final product (s) in each of following reactions:
50. How would you convert:
(i) Chlorobenzene to biphenyl
(ii) Propene to 1-iodopropane
(iii) 2-bromobutane to but-2-ene
Write the major product (s) in the following:
51. (i) Write the structural difference between starch and cellulose.
(ii) What type of linkage is present in nucleic acids?
(iii) Give an example of each fibrous protein and globular protein.
52. (i) Name the method of refining of nickel.
(ii) What is the role of cryolite in the extraction of aluminium?
(iii) What is the role of limestone in extraction of iron from its oxides?
53. (i) SO2 is reducing while TeO2 is an oxidizing agent.
(ii) Nitrogen does not form pentahalide.
(iii) ICl is more reactive than I2.
54. (a) For the complex [Fe (H2O)6]3+ , write the hybridization, magnetic character and spin of complex. (At. Number : Fe= 26)
(b) Draw one of the geometrical isomers of the complex [Pt (en)2Cl2]2+ , which is optically inactive.
55. An element crystallizes in a b.c.c. lattice with cell edge of 500pm. The density of the element is 7.5g cm-3. How many atoms are present in 300 g of the element?
56. (i) What is the role of Sulphur in the vulcanization of rubber?
(ii) Identify the monomer in the following polymer:
(iii) Arrange the following polymers in the increasing order of their intermolecular forces:
Terylene, Polythene, Neoprene
57. For the first order thermal decomposition reaction,C2H5Cl (g) → C2H4 (g) + HCl (g), the following data were obtained:
Time (in second)
Total pressure (in atm)
Calculate the log constant.
(Given log 2= 0.301, log 3=0.4771, log 4=0.6021)
58. Give reasons for the following:
(i) Aniline does not undergo Friedel-Crafts reaction.
(ii) (CH3)2NH is more basic than (CH3)3N in an aqueous solution.
(iii) Primary amines have higher boiling point than tertiary amines.
59. Define the following terms:
(i) Lycophilic colloid
(ii) Zeta potential
(iii) Associated colloids
60. Calculate the boiling point of solution when 4 g of MgSO4 (M=120 g mol-1) was dissolved in 100 g of water, assuming MgSO4undergoes complete ionization.
(Kb for water = 0.52 K kg mol-1)