12th Standard English Medium Chemistry Reduced Syllabus Annual Exam Model Question Paper - 2021

Download Tamil Nadu 12th Standard Chemistry question papers, model tests, one-mark questions, important questions, and public exam papers in PDF format. Free study materials and answer keys for TN State Board students.

Questions:

Multiple Choice Question

15 x 1 = 15

Oxidation of aniline with acidified potassium dichromate give

(a)

p-benzo quinone

(b)

benzoic acid

(c)

benzaldehyde

(d)

benzyl alcohol

The sugar unit present in nucleic acid is___________

(a)

a hexose

(b)

tetrose

(c)

pentose

(d)

glucose

The feasibility of a redox reaction can be predicted with the help of ______.

(a)

Electronegativity

(b)

Electrochemical series

(c)

Electron affinity

(d)

Equivalent conductance

With regard to the strength of acids and bases, Find the incorrect statement among the following.

(a)

Strong acid is one that completely dissociates in water

(b)

K_a is the dissociation constant

(c)

CH₃COOH is a weak acid

(d)

Smaller the K_a value, greater is the acid strength

Glycol \(\overset { 773K }{ \longrightarrow } \) 'A'. Identify 'A' _______.

(a)

(b)

\(\overset { { CH }_{ 3 } }{ \underset { CHO }{ | } } \)

(c)

(d)

Benzoic acid \(\overset { i){ NH }_{ 3 } }{ \underset { ii)\Delta }{ \longrightarrow } } A\overset { NaOBr }{ \longrightarrow } B\overset { NaN{ O }_{ 2 }/HCl }{ \longrightarrow } \) C 'C' is ______.

(a)

anilinium chloride

(b)

O – nitro aniline

(c)

benzene diazonium chloride

(d)

m– nitro benzoic acid

The phenomenon observed when a beam of light is passed through a colloidal solution is_______.

(a)

Cataphoresis

(b)

Electrophoresis

(c)

Coagulation

(d)

Tyndall effect

Which of the following fluro compounds is most likely to behave as a Lewis base?

(a)

BF₃

(b)

PF₃

(c)

CF₄

(d)

SiF₄

S-S bond is present in _______.

(a)

H₂S₂O₇

(b)

H₂SO₅

(c)

H₂S₂O₆

(d)

H₂S₂O₆

10.

A binary solid A+B has a structure with B^- ions constituting the lattice and A⁺ ions occupying 25% tetrahedral holes. Formula of the solid is _______.

(a)

A₂B

(b)

AB₂

(c)

(d)

AB₄

11.

Sodium magnesium and aluminum can be obtained from their ore by________.

(a)

electro metallurgy

(b)

pyro metallurgy

(c)

hydro metallurgy

(d)

smelting

12.

For a reaction Rate = k[acetone]^3/2 then unit of rate constant and rate of reaction respectively is _______.

(a)

(mol L^-1 S^-1),(mol^1/2L^1/2S^-1)

(b)

(mol^-1/2L^1/2s^-1),(mol L^-1s^-1)

(c)

(mol^1/2L^1/2s^-1),(mol L^-1s^-1)

(d)

(mol L s^-1),(mol^1/2L^1/2s)

13.

An excess of silver nitrate is added to 100ml of a 0.01M solution of Pentaaquachlorochromium (III)chloride. The number of moles of AgCl precipitated would be _______.

(a)

0.02

(b)

0.002

(c)

0.01

(d)

0.2

14.

The alloy of copper that contain Zinc is________.

(a)

Monel metal

(b)

Bronze

(c)

bell metal

(d)

brass

15.

Oxidation state of carbon in its hydrides _______.

(a)

(b)

-4

(c)

(d)

Generic 2

10 x 2 = 20

16.

Give the uses of mercury button cell.

17.

How will you convert benzaldehyde into the following compounds?
(i) benzophenone
(ii) benzoic acid
(iii) α-hydroxyphenylaceticacid.

18.

Complete the following reactions

ii) \(C_6H_5-CH_{2}CH(OH)CH(CH_3)_2 \overset{ConH_2SO_4}\longrightarrow\)

19.

What is the difference between a sol and a gel?

20.

When aqueous ammonia is added to CuSO₄ solution, the solution turns deep blue due to the formation of tetra ammine copper (II) complex,\({ [Cu({ H }_{ 2 }O)_4] }_{ (aq) }^{ 2+ }+ 4{ NH }_{ 3 }(aq)\rightleftharpoons { [Cu{ ({ NH }_{ 3 }) }_{ 4 }] }_{ (aq) }^{ 2+ }\) among H₂O and NH₃ Which is stronger Lewis base.

21.

If the rate of a reaction gets doubled as the temperature is increased from 27^oC to 37^oC. Find the activation energy of reaction?

22.

Give the reason for bleaching action of Cl₂.

23.

Draw the Cis and trans isomer of MA₂B₂ type

24.

Name the two steps involved in the extraction of crude metal

25.

What is catenation ? describe briefly the catenation property of carbon.

Generic 3

11 x 3 = 33

26.

Convert aniline to p-nitro aniline

27.

Give the structure of melamine formaldehyde resin.

28.

Justify the presence of keto group in C₂ in fructose.

29.

How is nitroglycerine prepared from glycerol?

30.

Explain the process of recharging of lead storage battery.

31.

Suggest a suitable reagent to prepare secondary alcohol with identical group using Grignard reagent.

32.

K_spof Al(OH)₃ is 1\(\times\)10^-15M. At what pH does 1.0×10^-3M Al³⁺ precipitate on the addition of buffer of NH₄Cl and NH₄OH solution?

33.

Account for the following:
(i) Cobalt (II) is stable in aqueous solution but in the presence of complexing reagents, it is easily oxidised.
(ii) The d¹ configuration is very unstable in ions.

34.

Benzene diazonium chloride in aqueous solution decomposes according to the equation \({ C }_{ 6 }{ H }_{ 5 }{ N }_{ 2 }Cl\longrightarrow { C }_{ 6 }{ H }_{ 5 }Cl+{ N }_{ 2 }\)Starting with an initial concentration of 10g L^-1, the volume of N₂gas obtained at 50 °C at different intervals of time was found to be as under:

t(min)	6	12	18	24	30	\(\infty \)
Vol of N₂ (ml)	19.3	32.6	41.3	46.5	50.4	58.3

Show that the above reaction follows the first order kinetics. What is the value of the rate constant?

35.

Distinguish tetrahedral and octahedral voids.

36.

How will you convert boric acid to boron nitride?

Generic 5

6 x 5 = 30

37.

Compound A of molecular formula C₃H₆O does not reduce Tollens reagent and Fehling's solution. Compound A undergoes Clemmensen reduction to give compound B of molecular formula C₃H₈. Compound A in the presence of cone.H₂SO₄ condenses to give an aromatic compound C of molecular formula C₉H₁₂. Identify A, B and C. Explain the reactions.

38.

Explain the following
(i) Reactant selectivity
(ii) Transition state selectivity
(iii) Product selectivity

39.

Complete the following reactions
(i) Cr₂O₇^2- ⟶
(ii) Cr₂O₇^2- + 6I^-+ 14H⁺ ⟶
(iii) Cr₂O₇^2-+ 3S^2-+ 14H⁺ ⟶
(iv) Cr₂O₇^2- + 3SO₂+ 2H⁺ ⟶
(v) Cr₂O₇^2- + 3Sn²⁺+ 14H⁺ ⟶
(vi) K₂Cr₂O₇ + 8H₂SO₄ + 3CH₃CH₂OH ⟶
(vii) 2MnO₄^- + 5(COO)^2-+ 6H⁺ ⟶
(viii) 2MnO₄^- + 10I^-+ 16H⁺ ⟶
(ix) 2MnO₄^- + 5S^2-+ 16H⁺ ⟶
(x) 2MnO₄^- + 5NO₂^- + 6H⁺ ⟶
(xi) 2KMnO₄ + 3H₂SO₄ + 5CH₃CH₂OH ⟶
(xii) 2MnO₄^- + 5SO₃^2- + 6H⁺ ⟶

40.

Account for the following:
(i) Reducing character decreases from SO₂ to TeO₂.
(ii) Xenon forms compounds with fluorine and oxygen only.

41.

What are the general characteristics of solids?

42.

Give the structure for the following compounds.
(i) pentaamminechlorocobalt (III) ion
(ii) Triamminetrinitrito- k N cobalt (III)
(ill) tetraammineaquabromidooobalt(III)nitrate
(iv) Dichloridobisethane-(1,2-diamine) cobalt (lIl) chloride
(v) Tetraamminecopper (lI) sulphate

Visit QB365-SLMS - https://www.qb365.in/slms/

Answers Key:

Multiple Choice Question

15 x 1 = 15

(a)
p-benzo quinone

(b)
Electrochemical series

(d)
Smaller the K_a value, greater is the acid strength

Scattering of light

BF₃ → electron deficient → Lewis acid
PF₃ → electron rich → Lewis base
CF₄ → neutral → neither Lewis acid nor base
SiF₄ → neutral → neither Lewis acid nor base

(d)
H₂S₂O₆

10.

(b)
AB₂

11.

(a)
electro metallurgy

12.

Rate = k[A]ⁿ
Rate = \(\frac{-\mathrm{d}[\mathrm{A}]}{\mathrm{dt}}\)
unit of rate = \(\frac{mol L^{-1}}{s}\)=mol L^-1/s^-1
unit of rate constant
\(=\frac{ (mol{ L }^{ -1 }{ S }^{ -1 }) }{ ({ mol }{ L }^{ -1 })^n } \)
= mol^1-nL^n-1s^-1
in the case
rate = k [Acetone]^3/2
n = 3/2
= mol^1-(3/2)L^(3/2)-1s^-1
(mol^-(1/2)L^(1/2)s^-1).

13.

The complex is [M(H₂O)₅Cl]Cl₂
1000 ml of 1 M solution of the complex gives 2 moles of Cl^- ions 1000 ml of 0.01 M solution of the complex will give
\(\frac{100 ml \times 0.01M \times 2Cl^-}{1000 ml \times 1M}\)
= 0.002 moles of Cl^- ions

14.

(d)
brass

15.

(a)
+4

Generic 2

10 x 2 = 20

16.

It has higher capacity and longer life. Used in pacemakers, electronic watches, cameras etc.

17.

(ii) benzoic acid

(iii) α - hydroxyphenylaceticacid.

18.

(i)
n-Nitro benzoate (Major Product)

(ii)

19.

S.no	Sol	Gel
(a)	The liquid state of collidal solution	The solid (or) semi solid stage of a colloidal solution.
(b)	Very low viscosity	Very high viscosity
(c)	It does not have definite structure.	It possesses definite structure.

20.

(i) According to Lewis theory a species that donates a pair of electron is called Lewis base.
(ii) Nitrogen more in NH₃ is less electro negative than oxygen in water. So the non - bonded electron pair on nitrogen is more available for sharing than a non - bonded electron pair on oxygen atom. So NH₃ is a stronger lewis base than H₂O.

21.

In \(\frac { { k }_{ 2 } }{ { k }_{ 1 } } =\frac { { E }_{ a } }{ R } \left[ \frac { { T }_{ 2 }-{ T }_{ 1 } }{ { T }_{ 1 }{ T }_{ 2 } } \right] \)
In 2 = \(\frac { { E }_{ a } }{ R } \) \(\left[ \frac { 10 }{ 300\times 310 } \right] \)
E_a = 9300 R In 2
= 53.4 kJ mol^-1

22.

(i) Bleaching action of Cl₂ is due to its oxidising property.
(ii) In aqueous solution, Cl₂ liberates nascent oxygen which brings about the oxidation of coloured substances present in vegetables and organic matter to colourless substances.
\(\mathrm{Cl}_{2}+\mathrm{H}_{2} \mathrm{O} \rightarrow 2 \mathrm{HCl}+\mathrm{[O}]\)
Coloured substance +[O] → colorless substance.

23.

MA₂B₂
[Pt(NH₃)₂Cl₂]

24.

(i) Conversion of ores into oxides.
(ii) Reduction of metal oxides.

25.

Catenation is an ability of an element to form chain of atoms.
The conditions for catenation.
(a) The valency of element is greater than or equal to two.
(b) Element should have an ability to bond with itself
(c) The self bond must be as strong as Its bond with other elements
(d) Kinetic inertness of catenated compound towards other molecules.
(e) Carbon possesses all the above properties and forms a wide range of compounds with itself and with other elements such as H, O, N, S and halogens.

Generic 3

11 x 3 = 33

26.

To get para product, the - NH₂ group is protected by acetylation with acetic anhydride. Then, the nitrated product is hydrolysed to form the product.

27.

28.

On oxidation with nitric acid, it gives glycolic acid and tartaric acids which contain smaller number of carbon atoms than in fructose.

This shows that a keto group is present in C-2.

29.

When glycerol is treated with a well cooled mixture of concentrated sulphuric acid and fuming nitric acid, nitroglycerine is formed.

30.

During recharge process, the role of anode and cathode is reversed and H₂SO₄ is regenerated.
Oxidation occurs at the cathode ( now act as anode)
\(\stackrel {+2}{{ PbS }O}_{ 4(s) }+2{ H }_{ 2 }O(l)\rightarrow \stackrel{+4}{ Pb }O_{ 2(S) }+{ SO }_{ 4(aq) }^{ 2- }\)
Reduction occurs at the anode (now act as cathode)
\({ PbS }O_{ 4(s) }^{ }+2{ e }^{ - }\rightarrow { Pb }_{ (s) }+{ SO }_{ 4(aq) }^{ 2- }\)
Overall reaction:
\({ 2PbS }O_{ 4(s) }^{ }+2{ H }_{ 2 }O(l)\rightarrow { Pb }_{ (s) }+{ Pb }O_{ 2(S) }+{ 4H }_{ (aq) }^{ + }+{ SO }_{ 4(aq) }^{ 2- }\)
Thus, the overall cell reaction is exactly the reverse of the redox reaction which takes place while discharging

31.

Acetaldehyde - CH₃-CHO

32.

\(Al(OH)_{3}\rightleftharpoons Al^{3+}_{(aq)}+3OH^{-}_{(aq)}\)
\(K_{sp}=[Al^{3+}][OH^{-}]^{3}\)
Al(OH)₃ precipitates when ionic product > K_sp
K_s = 1.0 \(\times\) 10^-15m, [Al³⁺] = 1.0 \(\times\) 10^-3m
1.0 \(\times\) 10^-15 = [1.0 \(\times\) 10^-3][OH^-]³
\(\left[\mathrm{OH}^{-}\right]^3=\frac{1.0 \times 10^{-15}}{1.0 \times 10^{-3}}\)
[OH^-]³ = 1.0 \(\times\) 10^-12
(or)
[OH^-]³ = 10^-4M
[H⁺][OH^-] = 10^-4M
[H⁺] = \(\frac{10^{14}}{10^{-4}}\) =10^-10
Here,
pH = 10
ie., At pH = 10, Al(OH)₃ gets precipitated on the addition of NH₄Cl & NH₄OH solution.

33.

(i) Cobalt (III) ion has greater tendency to form complexes than cobalt (II) ion. Therefore, Co (II) ion being stable in aqueous solution, changes to Co (III) ion in the presence of complexing reagents and get oxidised.
(ii) Ions of transition metals with d¹ configuration tend to lose one electron to acquire d⁰ configuration that is quite stable. Therefore, such ions (with d¹) undergo either oxidation or disproportionation, hence unstable.

34.

For a first order reaction
\(k=\frac { 2.303 }{ t } \log\frac { \left[ { A }_{ 0 } \right] }{ \left[ A \right] } \)
\(k=\frac { 2.303 }{ t } \log\frac { { V }_{ \infty } }{ { V }_{ \infty }-{ V }_{ 1 } } \)
V_∞= 58.3 ml.

t(min)	V_t	V_∞=V_t	\(k=\frac { 2.303 }{ t } \log\frac { { V }_{ \infty } }{ { V }_{ \infty }-{ V }_{ t } } \)
6	19.3	58.3-19.3=39.0	\(k=\frac { 2.303 }{ 6 } \log\left( \frac { 58.3 }{ 39 } \right) =0.0670\) min^-1
12	32.6	58.3-32.6=25.7	\(k=\frac { 2.303 }{ 12 } \log\left( \frac { 58.3 }{ 25.7 } \right) =0.06838\) min^-1
18	41.3	58.3-41.3=17.0	\(k=\frac { 2.303 }{ 18 } \log\left( \frac { 58.3 }{ 17 } \right) =0.06838\) min^-1
24	46.5	58.3-46.5=11.8	\(k=\frac { 2.303 }{ 24 } \log\left( \frac { 58.3 }{ 11.8 } \right) =0.0666\) min^-1
30	50.4	58.3 - 50.4 = 7.9	\(k=\frac{2.303}{30} \log \left(\frac{58.3}{7.9}\right)=0.067\) min^-1
			Mean value of k = 0.0674 min^-1

As the rate constants are constant through out it is a first order reaction.

35.

Tetrahedral voids Octahedral voids. 1. A void surrounded by 4 spheres occupying the corners of a tetrahedron. A void surrounded by 6 spheres along the corners of an Octahedron 2. It is formed when a sphere of second layer placed above the void of first layer. All the voids of first row which remain unoccupied from octahedral. 3. Co-ordination number is 4. Co-ordination number is 6. 4. The number of tetrahedral voids are equal to 2n. The number of Octahedral voids are equal to n.

36.

Fusion of urea with B(OH)_3' in an atmosphere of ammonia at 800 - 1200 K gives boron nitride.
B(OH)₃ + NH₃ \(\overset { \Delta }{ \longrightarrow } \) BN+ 3H₂O

Generic 5

6 x 5 = 30

37.

(i) Compound A of molecular formula C₃H₆O does not reduce Tollen's reagent and Fehling's solution.
(ii) Compound A undergoes Clemmensen reduction to give compound B of molecular formula C₃H₈

Compound	Compound Name	Formula
A	Acetone	CH₃COCH₃
B	Propane
C	Mesitylen

38.

(i) Reactant selectivity:
When bulkier molecules in a reactant mixture are prevented from reaching the active sites within the zeolite crystal, this selectivity is called reactant shape selectivity.
(ii) Transition state selectivity:
If the transition state of a reaction is large compared to the pore size of the zeolite, then no product will be formed.
(iii) Product selectivity:
It is encountered when certain product molecules one too big to diffuse out of the zeolite pores.

39.

(i) It oxidises ferrous salts to ferric salts.
Cr₂O₇^2- + 6Fe²⁺+ 14H⁺ ⟶ 2Cr³⁺ + 6Fe³⁺ + 7H₂O
(ii) It oxidises iodide ions to iodine
Cr₂O₇^2- + 6I^-+ 14H⁺ ⟶ 2Cr³⁺ + 3I₂ + 7H₂O
(iii) It oxidises sulphide ion to sulphur
Cr₂O₇^2- + 3S^2-+ 14H⁺ ⟶ 2Cr³⁺ + 3S + 7H₂O
(iv) It oxidises sulphur dioxide to sulphate ion
Cr₂O₇^2- + 3SO₂+ 2H⁺ ⟶ 2Cr³⁺ + 3SO₄^2- + H₂O
(v) It oxidises stannous salts to stannic salt
Cr₂O₇^2- + 3Sn²⁺+ 14H⁺ ⟶ 2Cr³⁺ + 3Sn⁴⁺ + 7H₂O
(vi) It oxidises alcohols to acids
2K₂Cr₂O₇ + 8H₂SO₄ + 3CH₃CH₂OH ⟶ 2K₂SO₄ +2Cr₂(SO₄)₃+ 3CH₃COOH + 11H₂O
(vii) It oxidises oxalic acid to CO2
2MnO₄^- + 5(COO)^2-+ 6H⁺ ⟶ 2Mn²⁺+ 10CO₂ + 8H₂O
(viii) It oxidises iodide ions to iodine
2MnO4^- + 10I^-+ 16H⁺ ⟶ 2Mn²⁺+ 5I₂+ 8H₂O
(ix) It oxidises sulphide ion to sulphur
2MnO₄^- + 5S^2-+ 16H⁺ ⟶ 2Mn²⁺+ 5S + 8H₂O
(x) It oxidises nitrites to nitrates
2MnO₄^- + 5NO^2- + 6H⁺ ⟶ 2Mn²⁺+ 5NO₃^- + 3H₂O
(xi) It oxidises alcohols to aldehydes.
2KMnO₄ + 3H₂SO₄ + 5CH₃CH₂OH ⟶ 2K₂SO₄ + 2MnSO₄ + 5CH₃CHO + 8H₂O
(xii) It oxidises sulphite to sulphate
2MnO₄^- + 5SO₃^2- + 6H⁺ ⟶ 2Mn²⁺+ 5SO₄^2- + 3H₂O

40.

(i) Stability of higher oxidation state decreases down the group from S to Te because stability of lower oxidation state increases down the group from S to Te.
(ii) Fluorine and oxygen are most electronegative and very reactive. So they can ionised noble gases and form compounds.

41.

(i) Solids have definite volume and shape
(ii) Solids are rigid and incompressible
(iii) Solids have strong cohesive forces.
(iv) Their constituents have fixed positions and can only oscillate about their mean positions.

42.

(i) [Co(NH₃)₅ CI]²⁺
(ii) [CO(NO₂)₃(NH₃)₃]
(iii) [Co(NH₃)₄H₂OBr](NO₃)₂
(iv) [Co(en)₂CI₂]CI
(v) [Cu(NH₃)₄]SO₄