ISC Chemistry 2021 Semester-1 Answer Key

Question 1

In a sodium chloride crystal, how many chloride ions are there around sodium ion?

(a) 3

(b) 4

(c) 6

(d) 8

Answer: (c) 6

Question 2

According to which law the solubility of a gas at equilibrium and constant temperature varies directly with the pressure of the gas, provided the gas does not undergo any chemical change during the dissolution?

(a) Raoult’s Las

(b) Nernst distribution Law

(c) Henry’s Law

(d) van’t Hoff Law

Answer: (c) Henry’s Law

Question 3

Which of the following statements is true for electrochemical cell?

(a) Cations move towards zinc electrode

(b) Cations move towards copper electrode

(c) Current flows from zinc electrode to copper electrode

(d) Electrons flow from copper to zinc electrode

Answer: (b) Cations move towards copper electrode

Question 4

In the extraction of copper from its sulphide ore, the metal is finally obtained by the reduction of cuprous oxide (Cu₂O) with:

(a) Cuprous sulphide (Cu₂S)

(b) Iron sulphide (FeS)

(c) Sulphur dioxide (SO₂)

Carbon monoxide (CO)

Answer:(a) Cuprous sulphide (Cu₂S)

Question 5

If chlorine gas is passed through hot and conc. aqueous sodium hydroxide solutions, the products formed have chlorine in different oxidation states. These oxidation ststes are indicated as:

(a) -1 and +5

(b) -1 and +3

(c) -1 and +1

(d) +1 and +5

Answer: (a) -1 and +5

Question 6

When ethyl chloride is heated with alcoholic AgCN, the main product formed is:

(a) Ethyl isocyanide

(b) Ethyl cyanide

(c) Ethyl nitrate

(d) Ethyl amine

Answer: (a) Ethyl isocyanide

Question 7

When phenol is treated with excess of bromine water, a white precipitate is formed. The compound formed is:

(a) m-bromophenol

(b) o and p-bromophenol

(c) 3,5-dibromophenol

(d) 2,4,6-tribromophenol

Answer: (d) 2,4,6-tribromophenol

Question 8

The ratio of number of atoms present in a face centred cubic, body centred cubic and simple cubic structures are respectively:

(a) 1:2:4

(b) 4:2:1

(c) 8:1:6

(d) 4:2:3

Answer: (b) 4:2:1

Question 9

Electrochemical equivalent(Z) is the amount of substance which gets deposited from its solutions on passing electrical charge equal to:

(a) 96500 coulombs

(b) 9650 coulombs

(c) 965 coulombs

(d) 1 coulomb

Answer: (d) 1 coulomb

Question 10

A solution containing components A and B follows Raoult’s Law. With reference to the statement which of the following options is correct?

(a) A-B attraction force is greater than A-A and B-B

(b) A-B attraction force is less than A-A and B-B

(c) A-B attraction force remains the same as A-A and B-B

(d) Total volume of solution is different from sum of volumes of both components A and B

Answer: (c) A-B attraction force remains the same as A-A and B-B

Question 11

What is used in the blast furnance to obtain iron from haematite ore?

(a) Electrolytic reduction

(b) Carbon dioxide

(c) Carbon monoxide

(d) Aluminium

Answer:(c) Carbon monoxide

Question 12

Copper metal on treatment with conc. nitric acid (HNO₃) gives

(a) Cu(NO₃)₂ + CuO + H₂O

(b) Cu(NO₃)₂ + NO + H₂O

(c) Cu(NO₃)₂ + NO₂ + H₂O

(d) Cu(NO₃)₂ + H₂SO₄ + H₂O

Answer: (c) Cu(NO₃)₂ + NO₂ + H₂O

Question 13

Haloform reaction DOES NOT take place with which of the following compounds

(a) Propanone

(b) 2-propanol

(c) Ethanol

(d) Methanol

Answer: (d) Methanol

Question 14

A solid has a structure in which ‘Y’ atoms are located at the corners of a cubic lattice, ‘O’ atoms at the centre of edges and ‘K’ atoms at the centre of the cube. What is the formula of this compound?

(a) KYO₂

(b) KYO₃

(c) K₂YO₃

(d) K₄YO₃

Answer: (b) KYO₃

Question 15

Formaldehyde when reacts with CH₃MgI forms an additional products, which on hydrolysis gives:

(a) Ethyl iodide

(b) Methyl alcohol

(c) Methyl iodide

(d) Ethyl alcohol

Answer: (d) Ethyl alcohol

Question 16

A solution of urea (molecular mass =60) contains 8.6 g per litre. It is isotonic with a 5% solution of a non-volatile and non-electrolyte solute. What will be the molecular mass of the solute?

(a) 34.9 g/ mol

(b) 349 g/mol

(c) 861 g/mol

(d) 3490 g/mol

Answer: (b) 349 g/mol

Question 17

The standard reduction electrode potential of Cu²⁺/Cu is =0.34V and that of Cr³⁺/Cr is -0.74V. These two electrodes are connected in their standard state to make an electrochemical cell. What will be the standard electrode potential (E^O) of this cell?

(a) 1.19V

(b) 1.08V

(c) 0.69V

(d) 1.83V

Answer: (b) 1.08V

Question 18

Acetyl chloride on heating with diethyl ether in the presence of anhydrous ZnCl₂ gives:

(a) Ethyl alcohol and acetic acid

(b) Methyl chloride and methyl alcohol

(c) Methyl acetate and methyl malcohol

(d) Ethyl acetate and ethyl chloride

Answer:(d) Ethyl acetate and ethyl chloride

Question 19

In compound XeF₂, XeF₄ and XeF₆ , the number of lone pair(s) on xe atom respectively is:

(a) 2,3,1

(b) 1,2,3

(c) 4,1,2

(d) 3,2,1

Answer: (d) 3,2,1

Question 20

The value of molal depresiion constant or cryoscopic constant (K_f) depends on which of the following?

(a) Nature of solvent

(b) Heat of the solution of the solute in the solvent

(c) Nature of solute

(d) Vapour pressure of the solution

Answer:(a) Nature of solvent

Question 21

Anti-Markownikoff addition of HBr is NOT observed in which of the following alkenes?

(a) Propene

(b) But-1-ene

(c) But-2-ene

(d) Pent-1-ene

Answer:(c) But-2-ene

Question 22

When phenol is treated with zinc dust, it gives:

(a) Benzoic acid

(b) Benzaldehyde

(c) Benzene

(d) Toluene

Answer:(c) Benzene

Question 23

The appearance of colour in solid alkali metal halides is generally due to:

(a) Schottky defect

(b) Frenkel defect

(c) Interstitial positions

(d) F-centres

Answer:(d) F-centres

Question 24

The ionic conductance at infinite dilution for Ba²⁺ and Cl^– iojns are 127 ohm^-1 cm² mol^-1 and 76 ohm^-1 cm² mol^-1 respectively. What will be the molar conductance of BaCl₂ at infinite dilution?

(a) 139.5 ohm^-1 cm² mol^-1

(b) 279.0 ohm^-1 cm² mol^-1

(c) 203.0 ohm^-1 cm² mol^-1

(d) 101.5 ohm^-1 cm² mol^-1

Answer:(b) 279.0 ohm^-1 cm² mol^-1

Question 25

When excess of ethanol is heated with conc. H₂SO₄ at 413K, which compound is obtained?

(a) Diethyl sulphate

(b) Ethyl hydrogen sulpjhate

(c) Ethoxy ethane

(d) Ethene

Answer: (c) Ethoxy ethane

Question 26

With reference to the extraction of metal, answer the following:

(i) What is the process of removing impurity from crude metal called?

(a) Roasting

(b) Calcination

(c) Refining

(d) Concentration

Answer: (c) Refining

(ii) Which of the following is not a method for the concentration of ores?

(a) Froth floatation

(b) Smelting

(c) Magnetic separation

(d) Gravity separation

Answer: (b) Smelting

Question 27

An alkyl halides reacts with metallic sodium in the presence of dry ether.

(i) What is this reaction known as?

(a) Frankland’s Reaction

(b) Sandmeyer’s Reaction

(c) Wurtz Reaction

(d) Kolbe’s Reaction

Answer: (c) Wurtz Reaction

(ii) An organic compound ‘A’ on reaction with sodium metal in dry ether gives a hydrocarbon, 2,2,3,3-tetramethyl butane, Identify compound ‘A’.

(a) tert-butyl chloride

(b) sec-butyl chloride

(c) iso-butyl chloride

(d) n-butyl chloride

Answer: (a) tert-butyl chloride

Question 28

Answer the following question with reference to the extraction of copper from its ore.

(i) Which one of the following is the sulphide ore?

(a) Cuprite

(b) Malachite

(c) Azurite

(d) Chalcopyrite

Answer: (d) Chalcopyrite

(ii) In the Bessemer converter, copper sulphide is reduced to copper by which one of the following reaction?

(a) Cu₂S + FeO = 2Cu + FeO + S

(b) Cu₂S + FeS = 2Cu + FeS₂

(c) Cu₂S + 2Cu₂O = 6Cu + SO₂

(d) Cu₂S + Fe = 2Cu + FeS

Answer: (c) Cu₂S + 2Cu₂O = 6Cu + SO₂

Question 29

Chlorobenzene is fused with aqueous sodium hydroxide at 623K and 300 atm follwed by hydrolysis with dil. HCl.

(i) The organic product formed is:

(a) Phenol

(b) Sodium phenoxide

(c) Benzene

(d) Cyclohexyl chloride

Answer: (a) Phenol

(ii) What is the name of the above reaction?

(a) Williamson’s synthesis

(b) Dow’s process

(c) Rosenmund’s reaction

(d) Kolbe’s reaction

Answer: (b) Dow’s process

Question 30

BrF₅ molecule is an interhalogen compound.

(i) What is the structure of the given molecule?

(a) Pentagonal bipyramidal

(b) Square pyramidal

(c) Square planar

(d) Tetrahedral

Answer: (b) Square pyramidal

(ii) What is the type of hybridisation shown by central atom of the above molecule?

(a) sp³

(b) sp

(c) sp³d²

(d) sp³d³

Answer: (c) sp³d²

Question 31

When ethene reacts with HBr, a compound (X) is formed. When compound (X) reacts with sodium ethoxide then compound (Y) is formed along with sodium bromide.

(i) Identify the compound (X)?

(a) C₂H₆

(b) C₂H₅Br

(c) CH₃Br

(d) C₂H₄Br₂

Answer: (b) C₂H₅Br

(ii) Identify the compound (Y)?

(a) CH₃OH

(b) C₂H₅OH

(c) CH₃OCH₃

(d) C₂H₅OC₂H₅

Answer: (d) C₂H₅OC₂H₅

Question 32

Extraction of silver metal is done mainly from argentite (Ag₂S) ore:

(i) The concentration ore on treatment with dil. NaOH solution and then followed by continuous agitation for several hours,which of the following products are obtained?

(a) AgCN and Na₂S

(b) Ag and NaCN

(c) Na₂SO₄ and Na₂SO₃

(d) Na[Ag(CN)₂] and Na₂S

Answer: (d) Na[Ag(CN)₂] and Na₂S

(ii) What is the above process of extraction of silver using dilute sodium cyanide known as?

(a) Deacon’s process

(b) Pattinson’s process

(c) Mac-Arthur-Forrest cyanide process

(d) Parke’s process

Answer: (c) Mac-Arthur-Forrest cyanide process

Question 33

Silver acetate is refluxed with bromine in carbon tetrachloride.

(i) What are the products formed?

(a) Ethane, silver bromide and water

(b) Ethanoyl bromide and silver

(c) Ethanoic acid and silver bromide

(d) Bromomehane, silver bromide and carbon dioxide

Answer: (d) Bromomehane, silver bromide and carbon dioxide

(ii) What is the above reaction known as?

(a) Finkelstein reaction

(b) Swartz reaction

(c) Hunsdiecker reaction

(d) Sandmeyer’s reaction

Answer: (c) Hunsdiecker reaction

Question 34

With reference to XeOF₄ molecule, answer the following questions:

(i) What is the type of htbridisation of Xe atom in the given molecule?

(a) sp³d

(b) sp³d²

(c) sp³d³

(d) sp³

Answer: (b) sp³d²

(ii) What is the geometry of this molecule?

(a) Octahedral

(b) Square pyramidal

(c) Square planar

(d) Tetrahedral

Answer: (b) Square pyramidal

Question 35

Phenol and ethyl alcohol can be distinguished by a single chemical test.

(i) Which of the following is the reagent used to distinguish phenol from ethyl alcohol?

(a) Solid PCl₅

(b) Dry sodium metal

(c) Neutral FeCl₃

(d) Acetyl chloride in presence of pyridine

Answer: (c) Neutral FeCl₃

(ii) Which colour is developed in the solution due to the addition of the above reagent to phenol?

(a) Blue

(b) Green

(c) Red

(d) Violet

Answer: (d) Violet

Question 36

Ozone is an allotropic form of oxygen. It acts as a powerful oxidising agent.

(i) During the oxidation of mercury (Hg) by ozone, the sub oxide (Hg₂O) formed dissolved in mercury causing it to lose its meniscus and starts sticking to the sides of glass. What is this phenomenon called?

(a) Branching of mercury

(b) Tailing of mercury

(c) Breaking of meniscus

(d) Distorted meniscus

Answer: (b) Tailing of mercury

(ii)Which of the following compounds is formed when ozone reacts with black lead sulphide?

(a) Blue coloured lead trioxide

(b) White coloured lead sulphate

(c) Green coloured lead oxide

(d) Red coloured tri lead tetroxide

Answer: (b) White coloured lead sulphate

Question 37

An element ‘X’ having atomic mass 60 has density 6.23 g/cc. The edge length of its cubic unit cell is 400 pm. (N_A = 6.023 x 10²³ mol^-1 )

(i) What is this type of unit cell known as?

(a) Body centred cubic

(b) Face centred cubic

(c) Simple cubic

(d) Side centred cubic

Answer: (b) Face centred cubic

(ii) What is the radius of an atom of this element?

(a) 210.5 pm

(b) 346.4 pm

(c) 141.4 pm

(d) 115.3 pm

Answer: (c) 141.4 pm

Question 38

0.76g of glucose ( molecular mass = 180 g/mol) is dissolved in 20 mL of aqueous solution at 298K. (R=0.0821 L/K mol)

(i) What is the osmotic pressure of solution at 298 K?

(a) 8.41 atm

(b) 0.48 atm

(c) 4.81 atm

(d) 5.16 atm

Answer: (d) 5.16 atm

(ii) What is the molarity of the glucose solution?

(a) 0.42 M

(b) 0.21 M

(c) 4.01 M

(d) 2.02 M

Answer: (b) 0.21 M

Question 39

A conductivity cell is filled with 0.05 M NaOH solution offering a resistance of 31.6 ohm. If the cell constant of the cell is 0.367 cm^-1 , calculate the following:

(i) The value of specific conductance:

(a) 1.29 x 10^-2 Ω^-1cm^-1

(b) 1.29 x 10^-3 Ω^-1cm^-1

(c) 1.16 x 10^-2 Ω^-1cm^-1

(d) 11.6 x 10^-2 Ω^-1cm^-1

Answer: (c) 1.16 x 10^-2 Ω^-1cm^-1

(ii) The value of molar conductance:

(a) 232.20 Ω^-1cm²mol^-1

(b) 23.22 Ω^-1cm²mol^-1

(c) 119.07 Ω^-1cm²mol^-1

(d) 165.36 Ω^-1cm²mol^-1

Answer: (a) 232.20 Ω^-1cm²mol^-1

Question 40

The radius of silver atom is 143.5 pm and it crystallises in face centred cubic arrangement.(Molecular mass of Ag=107.87, N_A = 6.023 x 10²³ mol^-1

(i) What is the edge length of the unit cell?

(a) 405.8 pm

(b) 40.6 pm

(c) 331.4 pm

(d) 287.0 pm

Answer:

(ii) What is the density of silver metal?

(a) 5.36 g/cc

(b) 8.60 g/cc

(c) 10.72 g/cc

(d) 7.07 g/cc

Answer:

Question 41

A solution contains 54g of glucose (molecular mass =180g/mol) in 250 g of water. (K_f for water = 1.86 K kg mol^-1 ).

(i) What will be the freezing point of this glucose solution?

(a) 276.402 K

(b) 270.768 K

(c) 370.402 K

(d) 272.563 K

Answer:

(ii) What will be the molality of this glucose solution?

(a) 1.20 m

(b) 0.12 m

(c) 2.40 m

(d) 0.24 m

Answer:

Question 42

The standard reduction electrode potential for Sn⁴⁺/Sn²⁺ couple is +0.15V and that for the Cr³⁺/Cr couple is -0.74V. These two couples in their standard state are connected to make a cell. (1 Faraday = 96500C/mol)

(i) What will be the value of E^o cell?

(a) +1.19V

(b) +0.89V

(c) +0.18V

(d) +1.83V

Answer:

(ii) What will be the value of standard Gibbs energy (∆G^o)?

(a) -650.3 kJ

(b) -515.3 kJ

(c) -226.4 kJ

(d) -406.8 kJ

Answer:

Question 43

Niobium crystallises in body centred cubic structure. Its density is 8.55g/cc and its atomic mass is 93g/mol. (N_A = 6.023 x 10²³ )

(i) What is the edge length of Nibobium?

(a) 314.50 pm

(b) 330.56 pm

(c) 340.43 pm

(d) 346.30 pm

Answer:

(ii) What is the atomic radius of Niobium?

(a) 136 pm

(b) 140 pm

(c) 143 pm

(d) 149 pm

Answer:

Question 44

5 moles of sucrose (molecular mass = 342 g/mol) dissolved in 1000g of water (molecular mass=18g/mol). Vapour pressure of pure water at 298K=4.57 mm Hg.

(i) What will be the vapour pressure of sucrose solution at the same temperature?

(a) 0.419 mm Hg

(b) 6.570 mm Hg

(c) 4.190 mm Hg

(d) 0.657 mm Hg

Answer:

(ii) What will be the mole fraction of sucrose in water?

(a) 0.8261

(b) 0.0826

(c) 0.4376

(d) 0.0435

Answer:

Question 45

A solution containing 2g of anhydrous barium chloride in 400 cc of water has a specific conductivity of 0.0058 S cm^-1. (At wt of Ba=137, Cl=35.5)

(i) What is the molarity of the above solution?

(a) 0.204 M

(b) 0.024 M

(c) 0.420 M

(d) 4.021 M

Answer:

(ii) What is the molar conductivity of the above solution?

(a) 241.67 S cm² mol^-1

(b) 261.47 S cm² mol^-1

(c) 247.17 S cm² mol^-1

(d) 361.47 S cm² mol^-1

Answer:

Question 46

Assertion : Nitration of chlorobenzene leads to the formation of m-nitro chlorobenzene.

Reason: Nitro (-NO₂ ) group is m-directing group.

(a) Both assertion and reason are true and reason is the correct explanation of the assertion.

(b) Both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) assertion is true but reason is false.

(d) Assertion is false but reason is true.

Answer:

Question 47

Assertion: Copper obtained after bessemerisation is known as blister copper.

Reason: Blisters are produced on the surface of the metal due to escaping of sulphur dioxide gas during cooling.

(a) Both assertion and reason are true and reason is the correct explanation of the assertion.

(b) Both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) assertion is true but reason is false.

(d) Assertion is false but reason is true.

Answer:

Question 48

Assertion: Phenol reacts with neutral ferric chloride (FeCl₃) and gives violet colour solution.

Reason: The violet colour solution is due to the formation of [Fe(OC₆H₅)₆]³⁺ complex ion.

(a) Both assertion and reason are true and reason is the correct explanation of the assertion.

(b) Both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) assertion is true but reason is false.

(d) Assertion is false but reason is true.

Answer:

Question 49

Assertion: Interhalogen compounds are more reactive than constituent halogens.

Reason: Bond between two different halogens is stronger than the bond between two similar halogen atoms.

(a) Both assertion and reason are true and reason is the correct explanation of the assertion.

(b) Both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) assertion is true but reason is false.

(d) Assertion is false but reason is true.

Answer:

Question 50

Assertion: The minerals from which the metals are conveniently and economically extracted are called ores.

Reason: All the metals can be extracted from their ores by one method.

(a) Both assertion and reason are true and reason is the correct explanation of the assertion.

(b) Both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) assertion is true but reason is false.

(d) Assertion is false but reason is true.

Answer: