This year, CBSE class 12 Chemistry paper is scheduled to be held on March 25. Thus with only about one and a half months 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 them 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 to help the students get a firm grip over the 2 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 6 to 10 are very short answer question and carry 2 marks each.
1. The chemistry of corrosion of iron is essentially an electrochemical phenomenon. Explain the reactions occurring during the corrosion of iron in the atmosphere.
2. Determine the values of equilibrium constant (Kc) and ΔG° for the following reaction:
Ni(s) + 2Ag+(aq) → Ni2+(aq) + 2Ag(s), Eo = 1.05 V
(1F = 96500 C/mol)
3. Distinguish between 'rate expression' and 'rate constant’ of a reaction.
4. State reasons for each of the following:
(i) The N−O bond in NO2- is shorter than the N -O bond in NO3-
(ii) SF6 is kinetically an inert substance.
State reasons for each of the following:
(i) All the P-Cl bonds in PCI5 molecule are not equivalent.
(ii) Sulphur has greater tendency for catenation than oxygen.
5. Assign reasons for the following:
(i) Copper (I) ion is not known in aqueous solution.
(ii) Actinoids exhibit greater range of oxidation states than lanthanoids.
6. Explain the following giving one example for each:
(i) Reimer-Tiemann reaction.
(ii) Friedel Craft's acetylation of anisole
7. How would you obtain
(i) Picric acid (2, 4, 6-trinitrophenol) from phenol,
(ii) 2-Methylpropene from 2-methylpropanol?
8. What is essentially the difference between α-form of glucose and β-form of glucose Explain?
9. Describe what you understand by primary structure & secondary structure of proteins.
10. Mention two important uses of each of the following:
(ii) Nylon 6
11. Express the relation among cell constant, resistance of the solution in the cell and conductivity of the solution. How is molar conductivity of a solution related to its conductivity?
The molar conductivity of a 1.5 M solution of an electrolyte is found to be 138.9 S cm2/ mol. Calculate the conductivity of this solution.
12. A reaction is of second order with respect to a reactant. How is its rate affected if the concentration of the reactant is (i) doubled (ii) reduced to half?
13. Which methods are usually employed for purifying the following metals:
Mention the principle behind each one of them?
14. Explain the following facts giving appropriate reason in each case:
(i) NF3 is an exothermic compound whereas NCl3 is not.
(ii) All the bonds in SF4 are not equivalent.
15. Complete the following chemical reaction equations:
16. Explain the mechanism of acid catalysed hydration of an alkene to form corresponding alcohol.
17. Explain the following behaviours:
(i) Alcohols are more soluble in water than the hydrocarbons of comparable molecular masses.
(ii) Ortho-nitrophenol is more acidic than ortho-methoxyphenol.
18. Describe the following giving the relevant chemical equation in each case:
(i) Carbylamines reaction
(ii) Hofmann's bromamide reaction
19. Complete the following reaction equations:
(i) C6H5N2Cl + H3PO2 + H2O →
(ii) C6H5NH2 + Br2 (aq) →
20. What are food preservatives? Name two such substances.
21. Account for the following:
(i) Schottky defects lower the density of related solids.
(ii) Conductivity of silicon increases on doping it with phosphorus.
22. Aluminium crystallizes in an FCC structure. Atomic radius of the metal is 125 pm. what is the length of the side of the unit cell of the metal?
23. The standard electrode potential (E°) for Daniel cell is + 1.1 V. Calculate ΔGo for the reaction:
Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s),
(1F = 96500 C/mol)
24. (a) For a reaction A+ B → P, the rate law is given by.
r = k [A]1/2 [B]2
What is the order of this reaction?
(b) A first order reaction is found to have a rate constant k = 5.5 x 10-14 s-1. Find the half life of the reaction.
25. (a) Name the method used for removing gangue from sulphide ores
(b) How is wrought iron different from steel?
26. Draw the structures of the following molecules:
27. How are interhalogen compounds formed? What general compositions can be assigned to them?
28. Explain the mechanism of the following reaction:
29. Write the equations involved in the following reactions:
(i) Reimer-Tiemann reaction
(ii) Williamson ether synthesis
30. Define thermoplastic and thermosetting polymers. Give one example of each.
What is a biodegradable polymer? Give an example of biodegradable aliphatic polyester.
31. An element with density 2.8g/cm3 forms of f.c.c. unit cell with edge length 4 × 10–8 cm. Calculate the molar mass of the element. [Given: NA = 6.022 × 1023 mol–1]
32. (i) What type of non-stoichiometric point defect is responsible for the pink colour of LiCl?
(ii) What type of stoichiometric defect is shown by NaCl?
How will you distinguish between the following pairs of terms?
(i) Tetrahedral and octahedral voids
(ii) Crystal lattice and unit cell
33. State Kohlrausch's law of independent migration of ions. Why does the conductivity of a solution decrease with dilution?
34. For a chemical reaction, R→P the variation in the concentration (R) vs. time (t) plot is given as
(i) Predict the order of the reaction.
(ii) What is the slope of the curve?
35. Explain the principle of the method of electrolytic refining of metals. Give one example.
36. Complete the following equations:
(i) P4 + H2O→
(ii) XeF4 + O2F2 →
37. Draw the structures of the following:
38. Write the equations involved in the following reactions:
(i) Reimer - Tiemann reaction
(ii) Williamson synthesis
39. Write the mechanism of the following reaction:
40. Write the names of monomers used for getting the following polymers:
41. Why do the transition elements have higher enthalpies of atomisation? In 3d series (Sc to Zn), which element has the lowest enthalpy of atomisation and why?
42. (i) Write down the IUPAC name of the following complex.
(ii) Write the formula for the following complex:
Potassium tetracyanonickelate (II)
43. (a) following reactions occurs at cathode during the electrolysis of aqueous sodium chloride solution:
Na+ (aq) + e- → Na(s) E = −2.71 V
H+ (aq) + e- → ½ H2 (g) E =0.0 V
On the basis of their standard reduction electrode potential (E) values, which reaction is feasible at the cathode and why?
(b) Why does the cell potential of mercury cell remain constant throughout its life?
44. Name the reagents used in following reactions:
(ii) CH3COOH ClCH2COOH
45. State Henry’s Law. Why do gases always tend to be less soluble in liquids as the temperature is raised?
State Raoult’s law for the solution containing volatile components. Write two differences between an ideal solution and non-ideal solution.
46. For a reaction:
Rate = k
(i) Write the order and molecularity of this reaction.
(ii) Write the unit of k.
47. Write chemical equations involved in following reaction:
(i) Hoffmann-bromamide degradation reaction
(ii) Carbylamine reaction
48. (a) Gas (A) is more soluble in water than gas (B) at the same temperature. Which one of these two gases have higher value of KH (Henry’s constant) and why?
(b) In a non ideal solution, what type of deviation shows the formation of maximum boiling azeotropes?
49. When a coordination compound CoCl3.6NH3 is mixed with AgNO3, 3 moles of AgCl are precipitated per mole of compound. Write
(i) Structural formula of the complex
(ii) IUPAC name of the complex
50. Write the structures of following:
What happens when?
(i) SO2 gas is passed through an aqueous solution Fe3+ salt?
(ii) XeF4 reacts with SbF5?