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Chemistry 56/3/2 2018-2019 CBSE (Science) Class 12 Question Paper Solution

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Chemistry
56/3/2
2018-2019 March
Marks: 70

Section A (5 marks)
[1]1
[1]1.a

Write IUPAC name of the complex K3 [Cr (C2O4)3] 

Concept: Nomenclature of Coordination Compounds - Formulas of Mononuclear Coordination Entities
Chapter: [9] Coordination Compounds
OR
[1]1.b

Using IUPAC norms write the formula of Hexaamminecobalt (III) sulphate. 

Concept: Amines - Nomenclature
Chapter: [13] Organic Compounds Containing Nitrogen
[1]2

Why is CH2 = CH - CH2 - Cl more easily hydrolysed than CH3 - CH2 - CH2 - Cl ?

Concept: Introduction of Haloalkanes and Haloarenes
Chapter: [10] Haloalkanes and Haloarenes
[1]3

Write the IUPAC name of the follow

\[\begin{array}\ce{\phantom{--..}O}\\\ce{\phantom{--..}||}\\ \ce{CH2=CH-C-CH3}\end{array}\]

Concept: Aldehydes and Ketones - Preparation of Aldehydes and Ketones
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[1]4
[1]4.a

What is the difference between a glycosidic linkage and a peptide linkage? 

Concept: Introduction of Proteins
Chapter: [14] Biomolecules
[1]4.b

What is the difference between a glycosidic linkage and a peptide linkage? 

Concept: Introduction of Proteins
Chapter: [14] Biomolecules
[1]5

 Arrange the following increasing order of their boiling point:
CH3CH2OH, CH3CHO, CH3–O–CH

Concept: Colligative Properties and Determination of Molar Mass - Elevation of Boiling Point
Chapter: [2] Solutions
[2]6
SECTION B
[2]6.a

 What happens when AgCl is doped with 2? CdCl What is the name of this defect? 

Concept: Imperfections in Solids - Types of Point Defects - Impurity Defects
Chapter: [1] Solid State
OR
[2]6.b
[1]6.b.i

What type of defect is shown by NaCl in 
 stoichiometric defects, and

Concept: Imperfections in Solids - Types of Point Defects - Stoichiometric Defects
Chapter: [1] Solid State
[1]6.b.ii

 non-stoichiometric defects?

Concept: Imperfections in Solids - Types of Point Defects - Stoichiometric Defects
Chapter: [1] Solid State
[2]7
[1]7.a

Account for the following:
Gabriel phthalimide synthesis is not preferred for preparing aromatic primary amines.

Concept: Amines - Preparation of Amines
Chapter: [13] Organic Compounds Containing Nitrogen
[1]7.b

 Account for the following: 
On reaction with benzene sulphonyl chloride, primary amine yields product soluble in alkali whereas secondary amine yields product insoluble in alkali.

Concept: Amines - Chemical Reactions of Amines - Reaction with Arylsulphonyl Chloride
Chapter: [13] Organic Compounds Containing Nitrogen
[2]8
[1]8.a

 Complete and balance the following equations: 
S+H2SO4(conc.)  → 

Concept: P - Block Group 16 Elements - Sulphuric Acid
Chapter: [7] P - Block Elements
[1]8.b

 Complete and balance the following equations: 
PCL3 + H2O → 

Concept: P - Block Group 15 Elements - Phosphorus Halides
Chapter: [7] P - Block Elements
OR
[1]8.c

Write balanced chemical equations involved in the following reactions:
Chlorine gas reacts with cold and dilute NaOH 

Concept: Compounds of Halogens
Chapter: [7] P - Block Elements
[1]8.d

Write balanced chemical equations involved in the following reactions: 
Calcium phosphide is dissolved in water. 

Concept: P - Block Group 15 Elements - Oxoacids of Phosphorus
Chapter: [7] P - Block Elements
[2]9
[1]9.a

 Draw structures of the following: 
XeF

Concept: P - Block Group 18 Elements - Concept of Group 18 Elements
Chapter: [7] P - Block Elements
[1]9.b

 Draw structures of the following: 
`S_2O_8^{2-}`

Concept: P - Block Group 16 Elements - Oxoacids of Sulphur
Chapter: [7] P - Block Elements
[2]10
[1]10.a

 Write the reaction that occurs at anode on electrolysis of concentrated 2 4 H SO using platinum electrodes. 

Concept: Introduction to Electrochemistry
Chapter: [3] Electrochemistry
[1]10.b

What is the effect of temperature on ionic conductance? 

Concept: Conductance of Electrolytic Solutions - Introduction
Chapter: [3] Electrochemistry
[2]11
[1]11.a

 Out of 0.1 molal aqueous solution of glucose and 0.1 molal aqueous solution of KCl, which one will have higher boiling point and why? 

Concept: Colligative Properties and Determination of Molar Mass - Introduction
Chapter: [2] Solutions
[1]11.b

 Predict whether van’t Hoff factor, (i) is less than one or greater than one in the following: 
CH3COOH dissolved in water 

Concept: Abnormal Molar Masses
Chapter: [2] Solutions
[2]12
[1]12.a

Write structures of compounds A and B in each of the following reactions: 

Concept: Structure of Amines
Chapter: [13] Organic Compounds Containing Nitrogen
[1]12.b

 Write structures of compounds A and B in each of the following reactions:

Concept: Amines - Preparation of Amines
Chapter: [13] Organic Compounds Containing Nitrogen
[3]13
[1]13.a

Define the following with a suitable example, of each: 
 Coagulation 

Concept: Preparation of Colloids
Chapter: [5] Surface Chemistry
[1]13.b

Define the following with a suitable example, of each: 
Multimolecular colloid

Concept: Colloids - Introduction
Chapter: [5] Surface Chemistry
[1]13.c

 Define the following with a suitable example, of each: 
 Gel

Concept: Colloids - Introduction
Chapter: [5] Surface Chemistry
OR
[1]13.d

Out of starch and ferric hydroxide sol, which one can easily be coagulated and why? 

Concept: Preparation of Colloids
Chapter: [5] Surface Chemistry
[1]13.e

What is observed when an emulsion is centrifuged?

Concept: Preparation of Colloids
Chapter: [5] Surface Chemistry
[1]13.f

 What is the role of promoters and poisons in catalysis?

Concept: Catalysis - Enzyme Catalysis
Chapter: [5] Surface Chemistry
[3]14
[1]14.a

 Following reaction takes place in the cell: 
`Zn(s) + Ag_2O(s)+H_2O(l) -> Zn^{2+}(aq) + 2Ag (s) + 2OH^- (aq)`
Calculate `Delta_r G^0` of the reaction

[Given ; `E^0_(Zn^{2+}//Zn)` = -0.76V

`E_((Zn^{2+}//Zn)) = 0.76V`

`E_(Ag^4//Ag)^0 = 0.80V, 1F = 96,500 C mol^-1 ]`
          

Concept: Nernst Equation - Electrochemical Cell and Gibbs Energy of the Reaction
Chapter: [3] Electrochemistry
[1]14.b

 How can you determine limiting molar conductivity,   0 m for strong electrolyte and weak electrolyte?

Concept: Conductance of Electrolytic Solutions - Variation of Conductivity and Molar Conductivity with Concentration
Chapter: [3] Electrochemistry
[3]15
[3]15.a

Write down the reaction taking place in blast furnace related to the metallurgy of iron in the temperature rnge 500 K – 800 K. What is the role of limestone in the metallurgy of iron? 

Concept: Refining
Chapter: [6] General Principles and Processes of Isolation of Elements
OR
[3]15.b
[1]15.b.i

What happens when Silver is leached with NaCN in the presence of air? 

Concept: Refining
Chapter: [6] General Principles and Processes of Isolation of Elements
[1]15.b.ii

What happens when Copper matte is charged into silica lined converter and hot air blast is blown? 

Concept: Refining
Chapter: [6] General Principles and Processes of Isolation of Elements
OR
[1]15.b.iii

What happens when Silver is leached with NaCN in the presence of air? 

Concept: Refining
Chapter: [6] General Principles and Processes of Isolation of Elements
[3]16

 A solution 0.1 M of Na2SO4 is dissolved to the extent of 95%. What would be its osmotic pressure at 027 ? C (R = 0.0821 L atm K-1 mol-1) .

Concept: Colligative Properties and Determination of Molar Mass - Introduction
Chapter: [2] Solutions
[3]17
[1]17.a

 An element crystallises in bcc lattic with a cell edge of 3 × 10-8cm. The density of the element is 6.89 g cm-3 . calculate the molar mass of element. (NA = 6.022 × 1023 mol-1)

Concept: Packing Efficiency - Efficiency of Packing in Body-centred Cubic Structures
Chapter: [1] Solid State
[2]17.b
[1]17.b.i

What type of semiconductor is obtained when 
Ge is doped with In?

Concept: Electrical Properties - Conduction of Electricity in Semiconductors
Chapter: [1] Solid State
[1]17.b.ii

 What type of semiconductor is obtained when 
 Si is doped with P? 

Concept: Electrical Properties - Conduction of Electricity in Semiconductors
Chapter: [1] Solid State
[3]18
[1]18.a

 Give reactions for the following: 
O – O single bond is weaker than S – S single bond. 

Concept: Concept of Group 16 Elements
Chapter: [7] P - Block Elements
[1]18.b

 Tendency to show –3 oxidation state decrease from Nitrogn (N) to Bismuth (Bi).

Concept: P - Block Group 15 Elements - Oxides of Nitrogen
Chapter: [7] P - Block Elements
[1]18.c

 Cl2 acts as a bleaching agent. 

Concept: P - Block Group 17 Elements - Concept of Group 17 Elements
Chapter: [7] P - Block Elements
[3]19
[1]19.a

Write the structures of monomers used to obtain the following polymers:
Buna S

Concept: P - Block Group 17 Elements - Concept of Group 17 Elements
Chapter: [7] P - Block Elements
[1]19.b

Write the structures of monomers used to obtain the following polymers:
Glyptal

Concept: Polymers - Classification of Polymers Based on Growth Polymerisation
Chapter: [15] Polymers
[1]19.c

Write the structures of monomers used to obtain the following polymers: 
 Nylon-6

Concept: Introduction of Polymers
Chapter: [15] Polymers
OR
[1]19.d

Arrange the following polymers in increasing order of their intermolecular forces: 
Polyvinylchloride, Neoprene, Terylene

Concept: Polymers - Classification of Polymers Based on Molecular Forces
Chapter: [15] Polymers
[1]19.e
[0.5]19.e.i

 Write one example each of :
 Natural polymer 

Concept: Proteins - Denaturation of Proteins
Chapter: [14] Biomolecules
[0.5]19.e.ii

 Write one example each of :
Thermosetting polymer 

Concept: Proteins - Denaturation of Proteins
Chapter: [14] Biomolecules
[1]19.f

What is the significance of number of 6,6 in the polymer nylon-6,6?

Concept: Types of Polymerisation Reactions - Condensation Polymerisation Or Step Growth Polymerisation
Chapter: [15] Polymers
[3]20
[1]20.a

Which one of the following is a disinfectant?
0.2% solution of phenol or 1% solution of phenol 

Concept: Therapeutic Action of Different Classes of Drugs - Antacids
Chapter: [16] Chemistry in Everyday Life
1
[0.5]20.b

 What is the difference between agonists and antagonists? 

Concept: Drug-target Interaction - Receptors as Drug Targets
Chapter: [16] Chemistry in Everyday Life
[1]20.c
[0.5]20.c.i

Write one example each of Artificial sweetener.

Concept: Chemicals in Food - Artificial Sweetening Agents and Food Preservatives
Chapter: [16] Chemistry in Everyday Life
[0.5]20.c.ii

Write one example each of Antacids.

Concept: Chemicals in Food - Artificial Sweetening Agents and Food Preservatives
Chapter: [16] Chemistry in Everyday Life
OR
[1]20.d

Define the following terms with a suitable example of each: 
 Antiseptics 

Concept: Therapeutic Action of Different Classes of Drugs - Antacids
Chapter: [16] Chemistry in Everyday Life
[1]20.e

Define the following terms with a suitable example of each: 
 Bactericidal antibiotics 

Concept: Therapeutic Action of Different Classes of Drugs - Antimicrobials
Chapter: [16] Chemistry in Everyday Life
[1]20.f

Define the following terms with a suitable example of each: 
 Cationic detergents

Concept: Cleansing Agents - Synthetic Detergents
Chapter: [16] Chemistry in Everyday Life
[3]21
[1]21.a

What happens when Salicylic acid is treated with (CH3CO)2 O/H+?

Concept: Carboxylic Acids - Chemical Reactions of Carboxylic Acids - Reactions Involving Cleavege of O-H Bond
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[1]21.b

What happens when Phenol is oxidised with Na2Cr2O7 / H+ ?

Concept: Preparation of Phenols from Haloarenes, Benzenesulphonic Acid, Diazonium Salts and Cumene
Chapter: [11] Alcohols, Phenols and Ethers
[1]21.c

What happens when Anisole is treated with 3 / CH Cl anhydrous  AlCl

Concept: Chemical Reaction of Ethers - Electrophilic Substitution
Chapter: [11] Alcohols, Phenols and Ethers
[3]22
[1]22.a

Write chemical equation in support of your answer. 
 Out of   Cl and  CH2- Cl,  which one is more reactive towards nucleophilic substitution reaction and why? 

Concept: Chemical Reactions of Haloalkanes and Haloarenes - Reactions of Haloarenes - Nucleophilic Substitution
Chapter: [10] Haloalkanes and Haloarenes
[1]22.b

Write chemical equation in support of your answer. 
 Out of  Cl and O2N Cl. which one is more reactive  towards nucleophilic substitution reaction and why?

Concept: Amines - Chemical Reactions of Amines - Reaction with Arylsulphonyl Chloride
Chapter: [13] Organic Compounds Containing Nitrogen
[1]22.c

 Out of    and  , which one is optically active and why ?

Concept: Isomerism in Coordination Compounds - Introduction
Chapter: [9] Coordination Compounds
[3]23
[1]23.a

Give one chemical test as an evidence to show that [Co (NH3)5Cl]  are ionisation isomers. 

Concept: Isomerism in Coordination Compounds - Introduction
Chapter: [9] Coordination Compounds
[1]23.b

[NiCl4]2- is paramagnetic while [Ni(CO)4] is  diamagnetic though both are tetrahedral. Why? (Atomic no. Ni = 28) 

Concept: Bonding in Coordination Compounds - Valence Bond Theory (VBT)
Chapter: [9] Coordination Compounds
[1]23.c

 Write the electronic configuration of Fe(III) on the basis of crystal field theory when it forms an octahedral complex in the presence of (i) strong field, and (ii) weak field ligand. (Atomic no.of Fe=26) 

Concept: Bonding in Coordination Compounds - Crystal Field Theory (CFT)
Chapter: [9] Coordination Compounds
[3]24
[1]24.a

What is the difference between fibrous protein and globular protein ?

Concept: Introduction of Proteins
Chapter: [14] Biomolecules
[1]24.b

Differentiable between the following: 
Essential amino acids Non-essential amino acids 

Concept: Proteins - Amino Acids
Chapter: [14] Biomolecules
[1]24.c

Differentiable between the following: 
Amylose and Amylopectin 

Concept: Carbohydrates - Structures of Glucose
Chapter: [14] Biomolecules
SECTION D
[5]25
[5]25.a
[5]25.a.i

Account for the following : 
Manganese shows maximum number of oxidation states in 3d series. 

Concept: Some Important Compounds of Transition Elements - Oxides and Oxoanions of Metals
Chapter: [8] "D" and "F" Block Elements
[1]25.a.ii

E0 value for  Mn3+ Mn2+ couple is much more positive than that for Cr3-/ Cr2-.

Concept: Some Important Compounds of Transition Elements - Oxides and Oxoanions of Metals
Chapter: [8] "D" and "F" Block Elements
[1]25.a.iii

Account for the following : 
 Ti4+ is colourless whereas V4+  is coloured in an aqueous solutions. 

Concept: General Properties of the Transition Elements (D-block)
Chapter: [8] "D" and "F" Block Elements
[2]25.b

 Write the chemical equation for the preparation of 4 KMnO from 2. MnO Why does purple colour of acidified permanganate solution decolourise when it oxidises Fe2- to Fe3+

Concept: Some Important Compounds of Transition Elements - Oxides and Oxoanions of Metals
Chapter: [8] "D" and "F" Block Elements
OR
[5]25.c
[1]25.c.i

Write one difference between transition elements and p-block elements with reference to variability of oxidation states.

Concept: P - Block Group 16 Elements - Oxoacids of Sulphur
Chapter: [7] P - Block Elements
[1]25.c.ii

Why do transition metals exhibit higher enthalpy of atomization? 

Concept: General Properties of the Transition Elements (D-block)
Chapter: [8] "D" and "F" Block Elements
[1]25.c.iii

Name an element of lanthanoid series which is well knwon to shown +4 oxidation state. Is it a strong oxidising agent or reducing agent? 

Concept: F-block Elements - The Lanthanoids
Chapter: [8] "D" and "F" Block Elements
[1]25.c.iv

What is lanthanoid contraction? Write the.............

Concept: F-block Elements - The Lanthanoids
Chapter: [8] "D" and "F" Block Elements
[1]25.c.v

 Write the ionic equation showing the oxidation of Fe(II) salt by acidified dichromate solutions. 

Concept: Some Important Compounds of Transition Elements - Oxides and Oxoanions of Metals
Chapter: [8] "D" and "F" Block Elements
[5]26
[2.5]26.a

Define order of reaction. How does order of a reaction differ from molecularity for a complex reaction? 

Concept: Integrated Rate Equations - First Order Reactions
Chapter: [4] Chemical Kinetics
[2.5]26.b

 A first order reaction is 50% complete in 25 minutes. Calculate the time for 80% completion of the reaction.

Concept: Integrated Rate Equations - First Order Reactions
Chapter: [4] Chemical Kinetics
OR
[2.5]26.c

The decomposition of a hydrocarbon has value of rate constant as 2.5×104s-1 At 27° what temperature would rate constant be 7.5×104 × 3 s-1if energy of activation is  19.147 × 103 J mol-1 ?

Concept: Temperature Dependence of the Rate of a Reaction
Chapter: [4] Chemical Kinetics
[2.5]26.d

 Write a condition under which a bimolecular reaction is kinetically first order. Give an example of  such a reaction. (Given : log2 = 0.3010,log 3 = 0.4771, log5 = 0.6990).

Concept: Temperature Dependence of the Rate of a Reaction
Chapter: [4] Chemical Kinetics
[5]27
[3]27.a
[1]27.a.i

 Predict the main product of the following reactions:

Concept: Temperature Dependence of the Rate of a Reaction
Chapter: [4] Chemical Kinetics
[1]27.a.ii

 Predict the main product of the following reaction:\[\begin{array}{c}
\ce{O\phantom{----}O\phantom{-}}\\
\ce{||\phantom{----}||\phantom{-}}\\
\ce{CH3-C-CH2-C-OCH3}
\end{array}\ce{->[(i)NaBH4][(ii)H+]}\]

Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Reduction
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[1]27.a.iii

Predict the main product of the following reactions:
\[\ce{CHO + CH_3CHO->[dil NaOH]}\]

Concept: Introduction of Aldehydes, Ketones and Carboxylic Acids
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[1]27.b

Give a simple chemical test to distinguish between 
 

Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Nucleophilic Addition Reactions
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[1]27.c

 Why is alpha (α) hydrogen of carbonyl compounds acidic in nature?

Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Reactions Due to A-hydrogen
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[3]27.d
[1]27.d.i

Write the main product formed when propanal reacts with the following reagents: 
2 moles of 3 CH OH in presence of dry HCl 

Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Nucleophilic Addition Reactions
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[1]27.d.ii

 Write the main product formed when propanal reacts with the following reagents: 
(ii) Dilute NaOH 
`CH_3CH_2CHO + NaOH(dil)-> `

Concept: Introduction of Aldehydes, Ketones and Carboxylic Acids
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[1]27.d.iii

Write the main product formed when propanal reacts with the following reagents: 
H2N- NH2  followed by heating with KOH in ethylene glycol. 

Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Nucleophilic Addition Reactions
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[2]27.e
[1]27.e.i

 Arrange the following compounds in increasing order of their property as indicated:
 F - CH2COOH, O2N - CH2 COOH CH3 COOH,HCOOH - acid character. 

Concept: Carboxylic Acids - Chemical Reactions of Carboxylic Acids - Reactions Involving Cleavege of O-H Bond
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[1]27.e.ii

 Acetone, Acetaldehyde, Benzaldehyde, Acetophenone – reactivity towards addition of HCN. 

Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Nucleophilic Addition Reactions
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids

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