Plus Two Chemistry Previous Year Question Paper 2017

Kerala Plus Two Chemistry Previous Year Question Paper 2017

Time: 2 Hours
Cool off time: 15 Minutes
Maximum: 60 Scores

General Instructions to Candidates

  • There is a ‘cool off time’ of 15 minutes in addition to the writing time of 2 hrs.
  • You are not allowed to write your answers nor to discuss anything with others during the ‘cool off time’.
  • Use the ‘cool off time’ to get familiar with the questions and to plan your answers.
  • Read questions carefully before you answering.
  • All questions are compulsory and the only internal choice is allowed.
  • When you select a question, all the subquestions must be answered from the same question itself.
  • Calculations, figures, and graphs should be shown in the answer sheet itself.
  • Malayalam version of the questions is also provided.
  • Give equations wherever necessary.
  • Electronic devices except nonprogrammable calculators are not allowed in the Examination Hall.

Plus Two Chemistry Previous Year Question Papers and Answers 2017 1

Question 1.
a. Identify the nonstoichiometric defect
i. Schottky defect
ii. Frenkel defect
iii. interstitial defect
iv. Metal deficiency defect
b. What type of substance could make better permanent magnets ferromagnetic or ferrimagnetic? Justify your answer.
c. In terms of Band theory write the differences between conductors and insulators.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 2
Plus Two Chemistry Previous Year Question Papers and Answers 2017 3

Question 2.
a. Henry’slaw is related to the solubility of a gas in a liquid.
i. State Henry’s law
ii. Write any two applications of Henry’s law.
b. 1000 cm3 of an aqueous solution of a protein contains 1.26 gm of the protein. The osmotic pressure of such a solution at 300 K is found to be 2.57 × 10-3 bar. Calculate the molar mass of the protein. (R = 0.083 L bar mol1K1)
Plus Two Chemistry Previous Year Question Papers and Answers 2017 4

Question 3.
a. Represent the galvanic cell based on the cell reaction given below:
Plus Two Chemistry Previous Year Question Papers and Answers 2017 5
b. Write the half-cell reactions of the above cell.
c. \(\wedge _{ m }^{ 0 }\) for NaCl, HCl and NaAc are 126.4, 425.9 and 91.0 S cm2 mol-1 respectively. Calculate \(\wedge _{ m }^{ 0 }\) for HAc.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 6

Question 4.
a. Plot a graph showing variation in the concentration of reactants against time for a zero order reaction.
b. What do you mean by zero order reaction?
c. The initial concentration of the first order reaction, N2O5(g) → 2NO2(g) + 1/2O2(g) was 1.24 × 10-2 mol L-1 at 300 K. The concentration of N2O5 after ‘ 1 ’ hour was 0.20 × 10-10 mol L-1. Calculate the rate constant of the reaction of 300 k.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 7

Question 5.
There are mainly two types of adsorption. They are physisorption and chemisorption.
a. Differentiate between physisorption and chemisorption.
b. Write any two applications of adsorption.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 8

Question 6.
Leaching is a process of concentration of ores. Explain the leaching of alumina from bauxite.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 9

Question 7.
Nitrogen forms a number of oxides and oxoacids.
a. Which of the following is a neutral oxide of nitrogen?
i. N2O
ii. N2O5
iii. NO2
iv.N2O4
b. Prepare a short write-up on Nitric acid highlighting its laboratory preparation, chemical properties and uses.
OR
Phosphorous forms a number of compounds, a. The gas liberated when calcium phosphide is treated with dil.HC/ is
i. Cl2
ii.H2
iii. PH3
iv. All of the above
b. Prepare a short write up on PCl3 and PCl5 highlighting the preparation and chemical properties of PCl3 and structure of PClr
Plus Two Chemistry Previous Year Question Papers and Answers 2017 11

Question 8.
a. Transition elements are d block elements.
i. Write any four characteristic properties of transition elements.
ii Cr2+ and Mn3+ have d4 configuration. But Cr2+ is reducing and Mn3 is oxidizing. Why?
b. Which of the following is not a lanthanoid element?
i. Cerium
ii. Europium
iii Lutetium
iv. Thorium
Plus Two Chemistry Previous Year Question Papers and Answers 2017 12
Plus Two Chemistry Previous Year Question Papers and Answers 2017 13

Question 9.
[CO(NH3)5S04]Cl and [Co(NH3)Cl]SO4 are coordination compounds.
a. Identify the isomerism shown by the above compounds.
b. Write the IUPAC names of the above compounds.
c. Identify the ligands in each of the above compounds.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 14

Question 10.
a. An ambident nucleophile is
i. Ammonia
ii Ammonium ion
iii Chloride ion
iv. Nitrite ion
b.Haloalkanes and Haloarenes are organohalogen compounds.
i. Suggest a method for the preparation of alkyl chloride.
ii. Aryl halides are less reactive towards Nucleophilic substitution reactions. Give reasons.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 15
Plus Two Chemistry Previous Year Question Papers and Answers 2017 16

Question 11.
a. Arrange the following compounds in the order of increasing boiling points: Ethanol, Propan1 o 1, Butan1 o 1, Butan2ol
b. In the lab, students were asked to carry out the reaction between phenol and cone. HN03. But one student, ‘A’ carried out the reaction between phenol and dil. HNOr Do you think that the student ‘A’ got the same result as others. Substantiate with suitable explanations. [Also write the chemical equations wherever necessary]
Plus Two Chemistry Previous Year Question Papers and Answers 2017 17

Question 12.
a. The product obtained when benzene is treated with carbon monoxide and hydrogen chloride in presence of anhydrous AlCl3 is
i. Chlorobenzene
ii. Phenol
iii. Benzaldehyde
iv. Benzoic acid
b. How will you carry out the following conversions?
Plus Two Chemistry Previous Year Question Papers and Answers 2017 18
OR

b. Explain the following:
i. Esterification
ii. Tollen’s test
iii. HVZ reaction
iv. Dicarboxylic acid
Plus Two Chemistry Previous Year Question Papers and Answers 2017 19
Plus Two Chemistry Previous Year Question Papers and Answers 2017 20

Question 13.
a. Classify the following amines as primary, secondary and tertiary
Plus Two Chemistry Previous Year Question Papers and Answers 2017 21
Identify the products B and C and write their formulae.
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Question 14.
a. Which of the following is a polysaccharide?
i. Maltose
ii. Sucrose
iii. Fructose
iv. Cellulose
b. Explain the amphoteric behavior of amino acid.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 23
Plus Two Chemistry Previous Year Question Papers and Answers 2017 24

Question 15.
a. Which of the following is not applicable to Nylon 6, 6?
i. Synthetic polymer
ii. Fiber
iii. Addition polymer
iv. Condensation polymer.
b. Differentiate between thermoplastics and thermosetting plastics. Write one example for each.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 25

Question 16.
‘Antibiotics, antiseptics, and disinfectants are antimicrobial drugs. Explain any one of the above-mentioned drugs with examples.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 26

Answers

Answer 1:
a. Metal deficiency defect
b. Ferromagnetic substances make better permanent magnets because, in the solid state, the metal ions of ferromagnetic substances are grouped together into small regions called domains. Thus, each domain acts as a tiny magnet. In an unmagnetized piece of a ferromagnetic substance, the domains are randomly oriented and their magnetic moments get canceled. When the substance is placed in the magnetic field, a strong magnetic effect is produced. This ordering of domains persists even when the magnetic field is removed and the ferromagnetic substance becomes a permanent magnet. However, this is not possible in ferrimagnetic substances,

c. In conductors, the valence band and conduction band overlap. Hence electrons can easily flow. In insulators the energy gap between the valence band and the conduction band is large, hence electrons cannot jump from one band to the other.

Answer 2.
a. i. It states that “the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas present above the surface of liquid or solution”. The most commonly used form of Henry’s law states that “the partial pressure(p) of gas in the vapor phase is proportional to the mole fraction of the gas(x) in the solution” and it is expressed as, P = KH.X, where KH is Henry’s law constant and ‘x’, is mole fraction of gas in solution.
ii.
1. To increase the solubility of CO2 in soda water and soft drinks, the bottle is sealed under high pressure.
2. To avoid the toxic effects of a high concentration of nitrogen in blood, the tanks used by scuba divers are filled with air diluted with helium.
b. p = 2.57 × 10-3 bar
V = 1000 cm3 = 1L
T = 300k
R = 0.083 L bar mol-1K-1
Plus Two Chemistry Previous Year Question Papers and Answers 2017 27

Answer 3.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 28

Answer 4.
a.
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b. In zero order reactions, the rate remains constant throughout the course of reaction i.e., the rate does not change with a change in concentration of reactants.
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Answer 5.
a. Physical adsorption (Physisorption):

  • Force of attraction between adsorbate and adsorbent are Van der Waals forces.
  • Lacks specificity.
  • Reversible.
  • Enthalpy of ads 40kJmol-1)
  • Occurs at low temperature.

Chemical adsorption (chemisorption):

  • Force of attraction I and adsorbent I bonds.
  • Highly specific.
  • Irreversible.
  • Enthalpy of advisor 240kJ/mol).
  • Occurs at high terr

b.

  • Production of high
  • Gas masks
  • Heterogenous cat?
  • Froth floatation pr
  • Control of humidity;
  • Chromatographic analysis

Answer 6.
Bauxite ore is treated with aqueous NaOH at 473-523K and 35-36 bar pressure. This way Al2O3 is leached out as sodium aluminate leaving the impurities behind.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 31
The aluminate in solution is neutralized by passing C02 gas and hydrated Al2O3 is precipitated.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 32
The sodium silicate remains in the solution and hydrated alumina is filtered, dried and heated to give back pure Al2O3
Plus Two Chemistry Previous Year Question Papers and Answers 2017 33

Another example: Gold or silver ore is leached with a dilute solution of NaCN or KCN in the presence of air from which the metal is obtained by replacement (using Zn as a reducing agent).

Answer 7.
a. N2O
b. In the laboratory, nitric acid is prepared by heating KNO3 or NaNO3 and concentrated H2SO4 in a glass retort.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 34
On large scale, it is prepared mainly by Ostwald’s process. This method is based upon catalytic oxidation of NH3 by atmospheric oxygen.
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Nitric oxide thus formed combines with oxygen giving NO2,
Plus Two Chemistry Previous Year Question Papers and Answers 2017 36
Nitrogen dioxide so formed dissolves in water to give HN03.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 37
NO thus formed is recycled and the aqueous HNO3 can be concentrated by distillation up to 68% by mass. Further concentration to 98% can be achieved by dehydration with concentrated H2SO4. Chemical properties
1. Acidic nature
Plus Two Chemistry Previous Year Question Papers and Answers 2017 38
2. Oxidizing agent behaves as a strong oxidizing agent because of its tendency to give nascent oxygen.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 39
Uses :
Used in the manufacture of various fertilizers, explosives, plastics, fibers, dyestuffs etc. It is used as a laboratory reagent and as an oxidizing agent. It is also used in the purification of silver an gold.
OR
a. (iii) pH3
b. Phosphorus forms two types of halides, PX3 (X = F, Cl, Br, I) and PX5 (X = F, Cl, Br). Preparation
It is obtained by passing dry chlorine overheated white phosphorus. P4 + 6CI2 → 4PCIIt is also obtained by the action of thionyl chloride with white phosphorus. P4 + 8SOCI2 → 4PCI3 + 4SO2 + 2S2CI2 Properties It is a colorless oily liquid and hydrolyzes in the presence of moisture.
PCI3 + 3H2O → H3PO3 + 3HCI It reacts with organic compounds containing OH group such as CH3COOH, C2H5OH.
3CH3COOH + PCI3 → 3CH3COCI + H3PO3 3C2H5OH + PCI3 → 3C2H5CI + H3PO3 It has a pyramidal shape as shown, in which phosphorus is sp3 hybridized. Preparation
Phosphorus pentachloride is prepared by the reaction of white phosphorus with an excess of dry chlorine. P4 + 10Cl2 → 4PCL5
It can also be prepared by the action of SO2CI2 on phosphorus.
P4 + 10SO2CI2 → 4PCI3 + 10SO5Properties PCI5 is a yellowish white powder and in moist air, it hydrolyzes to POCI3 and finally gets converted to phosphoric acid. PCI5 + H2O → POCI3 + 2HCI POCI3 + 3HO → HPO4 + 3HCI In gaseous and liquid phases, it has a trigonal bipyramidal structure as shown. The three equatorial P_CI bonds are equivalent, while the two axial bonds are longer than equatorial bonds.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 41
This is due to the fact that the axial bond pairs suffer more repulsion as compared to equatorial bond pairs. In the solid state, it exists as an ionic solid, [PCI4]+ [PCI6] in which the cation, [PCI4]+ is tetrahedral and the anion, [PCI8] cathedral.

Answer 8.
a. i. The transition elements are those elements which have partially filled subshells in their elementary form or in any one of its oxidation states. They have low ionization energy. They are malleable and ductile. They are good conductors of heat and electricity. High melting and boiling point.
ii. Cr2+ is reducing as its configuration changes from d4 to d3, the latter having a half-filled t2g level. On the other hand, the change from Mn2+ results in the half-filled (d5) configuration which has extra stability,
b. Thorium

Answer 9.
a. Ionization isomerism
b. [C0(NH3)5S04]CI- Pentaamminesulphatocobalt (III) chloride [CO(NH3)5Cl]SO– Pentamminechloridocobalt (III) sulfate
c. Counterion in a complex salt itself a potential ligand. ligands are Ct and SO42-

Answer 10.
a.iv. Nitrite ion
b.i. The preparation of alkyl chloride is carried out either by passing dry hydrogen chloride gas through a solution of alcohol or by heating a solution of alcohol in concentrated aqueous acid.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 42
ii.
1. Aryl halides are electron rich.
2. In aryl halides, the halogen is attached to an sp2 hybridized C, which is highly stable.
3. Because of the possible repulsion, it is less likely for the electron-rich arenes.
4. In the case of haloarenes, the phenyl cation formed as a result of self-ionization will not be stabilized by resonance and therefore, SN, a mechanism is ruled out.

Answer 11.
a. Ethanol < Propane -l-ol < Butan 2-ol < Butan -1-ol.
b. They don’t get the same result. Phenol with dilute nitric acid at low temperature (298 K) phenol yields a mixture of ortho and para nitrophenols.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 43
Phenol with concentrated nitric acid, phenol is converted to 2, 4, 6 trinitrophenol. The product is commonly known as picric acid. The yield of the reaction product is poor.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 44

Answer 12.
a. (iii) Benzaldehyde
Plus Two Chemistry Previous Year Question Papers and Answers 2017 45
Plus Two Chemistry Previous Year Question Papers and Answers 2017 46
OR
b.
i. Carboxylic acids react with alcohols in the presence of a strong acid catalyst like H2SO4 to form esters. The reaction is reversible and the forward reaction is called esterification,
Plus Two Chemistry Previous Year Question Papers and Answers 2017 47
ii. On warming an aldehyde with freshly prepared ammoniacal silver nitrate solution (Tollen’s reagent) a bright silver mirror is produced due to the formation of silver metal. The aldehydes are oxidized to corresponding carboxylate anion. The reaction occurs in alkaline medium.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 48
iii. HVZ reaction
Carboxylic acids having an α – hydrogen is halogenated at the α – position on treatment with chlorine or bromine in the presence of small amount of red phosphorous to give α – halocarboxylic acids. The reaction is known as Hell Volhard Zelinsky reaction.
iv. Carboxylic acids lose carbon dioxide to form hydrocarbons when their
Plus Two Chemistry Previous Year Question Papers and Answers 2017 49
Sodium salts are heated with soda lime (NaOH and CaO in the ratio of 3:1). The reaction is known as decarboxylation.

Answer 13.
Plus Two Chemistry Previous Year Question Papers and Answers 2017 50

Answer 14.
a.iv. Cellulose
b. In aqueous solution, the carboxyl group can lose a proton and amino group can accept a proton, giving rise to a dipolar ion known as twitter ion. This is neutral but contains both positive and negative charges. In winter ionic form amino acids show amphoteric behavior as they react both with acids and bases.

Answer 15.
a.iii. Addition polymer
b. Thermoplastic polymers These are the linear or slightly branched long chain molecules capable of repeatedly softening on heating and hardening on cooling. These polymers possess intermolecular forces of attraction intermediate between elastomers and fibers. Some common thermoplastics are polyethylene, polystyrene, polyvinyls, etc.

Thermosetting polymers These polymers are cross-linked or heavily branched molecules, which on heating undergo extensive cross-linking in molds and again become infusible. These cannot be reused. Some common examples are bakelite, urea formaldehyde resins, etc

Answer 16.
Antibiotics: These are chemical substances which are produced wholly or partly by chemical synthesis, which in low concentration inhibits the growth or destroys microorganisms by intervening in their metabolic processes, eg., penicillin, streptomycin, ampicillin, tetracycline. Antibiotics are of two types:
Bactericidal antibiotics: They have killing (cidal) effect on microbes, eg., pencil in, ofloxacin, etc.
Bacteriostatic antibiotics: They have an inhibitory (static) effect on microbes, eg., Tetracycline, chloramphenicol, etc.
Antibiotic spectrum: The range of microorganisms attacked by an antibiotic is called its spectrum.

  • Antibiotics which kill or inhibit a wide range of Gram-positive and Gram-negative bacteria are called broad-spectrum antibiotics.
    eg., Ampicillin, tetracycline, ofloxacin.
  • Those which are effective mainly against Gram-positive or Gram-negative bacteria are narrow spectrum antibiotics.
    eg., penicillin G.

Plus Two Chemistry Previous Year Question Papers and Answers

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