12th Chemistry Model Question Paper: வேதியியலில் வெற்றி நிச்சயம்- இதோ பிளஸ் 2 மாதிரி வினாத்தாள்!

TN 12th Chemistry Model Question Paper 2024: 12ஆம் வகுப்பு வேதியியல் பாடத்துக்கான மாதிரி வினாத்தாள் இதோ!

12ஆம் வகுப்பு வேதியியல் பாடம்

10, 12ஆம் வகுப்பு மாணவர்களுக்கான பொதுத் தேர்வு மாதிரி வினாத்தாள்களை, ABP Nadu ஊடகம் ஆண்டுதோறும் வெளியிட்டு வருகிறது. அந்த வகையில்,12ஆம் வகுப்பு பாடங்களுக்கான மாதிரி வினாத்தாள்களை தினந்தோறும் வெளியிட்டு வருகிறோம்.

12ஆம் வகுப்பு வேதியியல் பாடத்துக்கான மாதிரி வினாத்தாள் இதோ!

MODEL QUESTION PAPER

XII CHEMISTRY

Time:3.00 hours                                                                                        Total Marks:70

                                                                  PART - I

I.Choose the most suitable answer from the given four alternatives.

 

1. wolframite ore is separated from tinstone by the process of

a)smelting     b)calcination   c)Roasting  d)Electromagnetic Seperation

 

2.The element that does not show catenation among the following p-block elements is

a)Carbon      b)silicon         c) lead       d)germarium

 

3.The basicity of pyrophosphorous acid ( ) is

1. a) 4 b)2          c)3           d)5

4.Which one of the following iron has the same number of unpaired electrons as             present in

1. a) b) c)        d)

 

5.oxidation state of Nickel in [Ni ]

     a)2             b)0              c)1              d)3     

 

6.The vacant space in Fcc lattice unit cell is

     a)48%        b)23%        c)32%      d)26%

 

7.After 2 hours, a radioactive substance  becomes (  of origin amount .Then the half life (in min)

a)60 minutes        b)120 minutes       c)30 minutes        d)15 minutes 

 

8. of a saturated solution of Ca ( is 9.The solubility product (ksp) of Ca 

a)0.5  x10^-15              b) 0.25x10-¹⁰            c)0.125x10^-15           d) 0.5x10^-10

 

9. which charging lead storage battery
10. a) PbSo₄ on cathode is reduced to Pb

b)PbSo₄on anode is oxidised to Pbo₂

1. c) PbSo₄ on anode is reduced to Pb

d)PbSo₄on cathode is oxidised to Pb

10.Milk is colloidal solution of

1. a) Solid in gas b)gas is gas c)Liquid in Liquid   d)gas in Liquid

 

11. Cold dilutealkaline KMnO₄is known is
12. a) Schiff ‘s request b) Fehling ‘s request c) Bayer ‘s request   d) Nessler ‘s request

 

12.The formation of cyanohydrin from acetone is an example of

1. a) nucleophilicsubstitution b) electrophilic substitution c)electrophilic addition
2. d) nucleophilic addition

 

13. which one of the following will not undergo Hofmann bromide reaction?
14. a) CH₃ CO NHCH₃ b) CH₃CH₂CONH₂ c) CH₃CONH₂      d) C₆H₅CONH₂

 

14. The control dogma of molecular genetics stats that the genetic information flows from:
15. a) Amino acids -Protein-DNA b) DNA-Carbohydrates-Protein

c)DNA-RNA-Protein     d) DNA-RNA-Carbohydrate

 

15.Asprin is a/an

1. a) acetylsalicylic acid b) benzoyl salicylic acid c) chlorobenzoic acid
2. d) anthranilic acid

 

 

PART-II

                                                                                                                            

Answer any 6 questions.Question No.24 is compulsory.                                                    6×2=12                                 

16. 16. Give the limitations of Ellinghamdiagram?

• It does not explain rate of reaction.
• It does not give any idea about the possibility of other reactions taking place.
• AG is assuming at equilibrium condition, but it is not always true.

 

17. What is burnt alum?

• At475K-500K potash alum loses water of hydration and swells up
• The swollen mass is known as burnt alum.

 

18.Which is more stable? Fe³⁺ orFe²⁺ explain.

Electronic configuration of Fe³⁺ is [Ar] 3d⁵

Electronic configuration of Fe²⁺is[Ar]3d⁶

Fe³⁺ is more stable, since it has half-filledorbitals .

 

19.Why ZnO turns yellow on heating?

On heating ZnO loses oxygen atom and forms a free Zn²⁺ ion.

This Zn² ion and electrons occupy the interstitial position.

This is due to formation of Metal excess defect.

20.Write a note on catalytic poison?

Substance which decreases the activity of a catalyst

• In the manufacture of ammonia by Haber's process, H₂S acts as a catalytic poison to Fe catalyst

 

21. Give the tests for Carboxylic acids.

Change Blue Litmus paper into Red Colour

Brisk effervescence with Sodium bicarbonate solution

When heated with Alcohol and con. H₂SO₄. Fruity odour ester is obtained.

 

22.Write a note on Carbylamine reaction. (Test for primary amines)

 

Methyl amine + Chloroform Methylisocyanide

CH₃NH₂ + CHCI₃, +3КОН CH₃NC + 3KCl + 3H₂O

 

23.Write the preparation of Buna-S?

PART -III

 

Answer any question.Question No-33 is compulsory                                                        6x3=18

 

25. Differentiate White phosphorus and red phosphorus

White phosphorus	Red phosphorus
Poisonous in nature	It is not poisonous
Garlic smell	Odourless
It shows Phosphorescence	Does not show Phosphorescence.
Its ignition temperature is very low	It does not ignite at low temperatures

 

 

 

 

26. What is lanthanoid contraction and what are the effects of lanthanoid contraction?

As we move across 4f series, the atomic and ionic radii of Lanthanoids show gradual decrease with increase in atomic number.This decrease in ionic size is called Lanthanoid contraction.

Cause of lanthanoid contraction

 The shielding effect of 4f electrons are poor.

 Effects of lanthanoid contraction

• Size and radius of ions decreses
• Basicity decreases
• Covalent character increases

The elements of second and third transition series resemble each other more closely.

27. A solution of [Ni (H2O)6]2+ is green where as the solution of [Ni (CN)4]2- is colourless explain.

 

• [Ni (H2O)6]²⁺ H₂O is a weaker ligand. Don't pair d electrons.

 

Presence of unpaired electron, d-d transaction.Therefore green in colour.

 

 [Ni (CN)₄ ]^2- CN^- is a strong ligand, d electrons are paried.

 

Absence of unpaired electron. No d-d transaction. Therefore colourless.

 

29.Define std hydrogen Electrode (SHE)

 

The emf of a cell is the sum of the electrode potentials at the cathode and anode,

Ecell = (Eox) anode + (Ered)cathode

• Standard Hydrogen Electrode (SHE) is used as the reference electrode.

Emf is zero volt.

• It consists of a platinum electrode in contact with IM HCI solution and 1 atm hydrogen gas.
• The hydrogen gas is bubbled through the solution at 25°C
• SHE can act as a cathode as well as an anode.

The Half cell reactions are given below

• Anode - oxidation

H₂ 2H⁺ + 2e^-                                E° = 0 v

• Cathode reduction

2H⁺ + 2 H₂                                E° = 0 v

 

30.Expalin intermediate compound formation theory of catalysis with an example?

   It is based on a homogeneous catalysed reaction

                               A+B   AB

         Step -I :  A+C (intermediate compound)

         Step -II:  AC+B

 

Example

       2SO_2(g) +O_2(g) 2SO₃

 

      Step-I:    2NO +O₂ 2NO₂

     Step-II:     NO2+SO2 SO3+NO

 

 

 

 

32. Write a short note on peptide bond

  The carboxyl group of the first amino acid react with the amino group of the second amino acid to form peptide bond.

33. Identify A,B and C

PART-IV

Answer all the questions                                                                                                                                                    

34. a)

1. i) Explain the Magnetic separation process (3)

• It is based on the difference in the Magnetic properties of the ore and the impurities
• It is used to concentrate ferromagnetic ores.
• Tin stone can be separated from the wolframite impurities.
• The powered ore is added on an electro magnet containing a moving belt on a magnetic rollers.
• The magnetic ore falls near the magnet.
• The non magnet parts fall away from the magnet.

ii) Why HF is not stored in glass bottles? (2)

                Monist hydrofluoric acid HF(not dry ) rapidly react with sodium silicate in glass.

                 SiO₂+4HF SiF₄+2H₂O

                 Na₂SiO₃+6HF Na₂SiF₆+3H₂O

 

                                                            OR

b)Write a note on zeolites? (3)

• Zeolites are three dimensional crystalline solids containing aluminium,silicon and oxygen.
• Si and Al atoms are tetrahedrally coordinated with oxygen atoms .
• They are Hydrated solidum alumino silicate (NaO.Al₂O₃.xSiO₂.yH₂O).
• They have porous structure in which the monovalent sodium ions and water molecules are loosely held.
• Water molecules move freely in and out of these pores.
• They have crystalline structure looks like a honeycomb consisting of a network of interconnected tunnels and cages.
• The crystal to act as a molecular sieve.

ii)Write the oxidation state ,co-ordination number Ligand central metal atom in K₄[Fe(CN)₆] complex (2)

                         Complex                                        K₄[Fe(CN)₆]                                                      

Oxidation state                               +2

Co ordination number                    6

Ligand                                             CN^-

Central metal atom                      Fe²⁺

  

35.a) Calculate the percentage efficiency of packing in case of body centered cubic crystal. (5)

    

35. B. Write the pastulates of werner’s theory. (5)

  The central metal atom exhibit two type of velence.

1. Primary valency secondary valency.

 

PRIMARY VALENCY	SECONDARY VALENCY
Oxidation number of the central metal ion	Coordination number of the central metal ion
It is non directional	It is directional
Ionisable valency	Non Ionisable valency
Always satisfied by negative ions	Satisfied by negative ions OR neutral molecules OR positive ions

 

There are two spheres of attraction around a metal atom / ion in a complex.

 

1. The inner sphere (coordination sphere)

     The group present in this sphere are firmly attached  to the  central metal ion .

2.The out sphere (ionisation sphere)

 The group present in this sphere are loosly attached  to the  central metal ion .

 

Structure of compound [Co(NH₃]Cl₃

 

Limitation of werner’s theory.

It does not explain the colour and magnetic properties of coordination compounds.

 

36. a) I) Derive henderson - hasselbatch quation (3)

 

HA + H₂O = [H₃O⁺] = (acid)eq

                                      (base)eq

 

Due to common ion effect

 

 (acid)eq = (acid) : (base)eq = (salt)

 

[H₃O⁺] = K_a (acid) / ( salt )

 

Revers the sign on both sides

 

-log  [H₃O⁺]  = -log K_a -log (acid) / ( salt )

 

We know that

 

PH = - -log  [H₃O⁺]  and  pK_a  = -log K_a

 

PH =   pK_a   -  log  (acid) / ( salt )

 

PH =   pK_a   + log  (acid) / ( salt )

 

Similarly for absic buffer

 

POH =  pK_b   + log  (acid) / ( salt )

 

 

1. ii) write a note on sacrificial protection. (2)

sacrificial protection (cathodic prodection)

1. sacrificial anode - zinc
2. Cathode - iron
3. So iron is prodected,but Zn is corroded

                      (or)

1. b) Explain dispersion methods of preparation of colloids. (5)

 

1. mechanical dispersion

• The colloidal mill corists of two metal places roating in opposite direction at very high speed.
• The solid is ground to colloidal dimension.
• Colloidal solutions of onk and grapite as pepared.

 

2. Peptisation

 

     The disperson of a precipitated matirial into colloidal solution by the action of an electrolyte in solution is termed as peptisation.

                   Hcl

   Agcl                       Agcl

 Precipitate                         collide

37. a) i. How will you distinguish between primary,secondary and tertiary amines? (3)

 

Reagent	Primary amines	Secondary  amines	Tertiary amines
Nitrous acid	Forms alcohol	Forms N-nitroso amine	Forms  salt
Carbylamine reaction CHCl3 / KOH	Forms  Carbylamine	No rection	No rection
Mustard oil rection CS2 / Hgcl2	Forms alkyl isothiocynate	No rection	No rection
Acetyl chloride	Forms N-alkyl acetinide	Forms N,N-do alkyl acetamide	No rection
Alkyl halides	3  molecules of alkyl halide,quarternary ammonium salt is formed	2 molecules of alkyl halide,quarternary ammonium salt is formed	1 molecules of alkyl halide,quarternary ammonium salt is formed

 

 

1. ii) Write the uses of diethyl ether. (2)

• Anesthetic agent in surgery
• Used as a refrigerant
• Solvent for organic reactions.

 

                                  (or)

 

1. b) Mechanism of cannizaro reaction (5)

Cannizaro reaction is a characteristic reaction of aldehyde having na  α

 - hydrogen

                                       Dil.NaOH

C₆H₅CHO+C₆H₅CHO          ------->                C₆H₅CH₂OH+ C₆H₅COON_a

 

Step : 1 Attack of OH^- On the carbonyl carbon.

 

38. a). Elucidate the structure of glucose (5)

 

• Molecular formula C₆H₁₂O₆

 

• Glucose + P/H1 At  373k                      n-hexane.6 carbon atoms are bonding linearly

 

• Glucose + HCN                      cyanohydrins presence of carbonyl group.

 

• Glucose + acetic anhydride + pyridine                       penta acetate. It contains 5 OH groups

 

• Glucose + tollens reagent reduction to metalic silver.presence of aldehyde group

 

                                                       (or)

 

b). i) Write a note on vulcanization of rubber. (3)

 

• Natural rubber is mixed 3-5% sulphur and heated at 100- 150⁰ c causes cross linking of the cis - 1,4-polyisopreene chains through disulphide (-s-s-) bonds.
• The properties of natural rubber can be modified by the process called vulcanization.
• 1 to 3% sulphur rubber is soft and stretchy
• 3 to 10% sulphur rubber is harder flexible.

 

 

1. ii) How the tranquilizers work in body? (2)

 

• They are neurolgically active drugs.
• They acts on the central nervous system by blocking the neuro transtmitter dopomine in the brain.
• The treatment of stress,sleep disorders and severe mental disease.
• Major tranquilizers - haloperidol,clozapine
• Minor tranquilizers - valium,alprazolam

இதையும் வாசிக்கலாம்: 12th Physics Model Question Paper: இனி இயற்பியலும் இனிமைதான்- பிளஸ் 2 மாதிரி வினாத்தாள் இதோ!