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.

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.

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)

Question 3.
a. Represent the galvanic cell based on the cell reaction given below:

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.

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, N₂O_5(g) → 2NO_2(g) + 1/2O_2(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.

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.

Question 6.
Leaching is a process of concentration of ores. Explain the leaching of alumina from bauxite.

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 PCl_r

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

Question 9.
[CO(NH₃)₅S0₄]Cl and [Co(NH₃)₅ 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.

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.

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]

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?

OR

b. Explain the following:
i. Esterification
ii. Tollen’s test
iii. HVZ reaction
iv. Dicarboxylic acid

Question 13.
a. Classify the following amines as primary, secondary and tertiary

Identify the products B and C and write their formulae.

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.

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.

Question 16.
‘Antibiotics, antiseptics, and disinfectants are antimicrobial drugs. Explain any one of the above-mentioned drugs with examples.

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 = K_H.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

Answer 3.

Answer 4.
a.

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.

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.

The aluminate in solution is neutralized by passing C0₂ gas and hydrated Al₂O₃ is precipitated.

The sodium silicate remains in the solution and hydrated alumina is filtered, dried and heated to give back pure Al₂O₃

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.

On large scale, it is prepared mainly by Ostwald’s process. This method is based upon catalytic oxidation of NH₃ by atmospheric oxygen.

Nitric oxide thus formed combines with oxygen giving NO₂,

Nitrogen dioxide so formed dissolves in water to give HN03.

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

2. Oxidizing agent behaves as a strong oxidizing agent because of its tendency to give nascent oxygen.

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 → 4PCI₃ It 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.

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 t_2g 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]SO₄ – Pentamminechloridocobalt (III) sulfate
c. Counterion in a complex salt itself a potential ligand. ligands are Ct and SO₄^2-

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.

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.

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.

Answer 12.
a. (iii) Benzaldehyde


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,

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.

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

Sodium salts are heated with soda lime (NaOH and CaO in the ratio of 3:1). The reaction is known as decarboxylation.

Answer 13.

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