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Grade XI

Chemistry(Mock Test)

Mock Test Chemistry Maximum Marks:70 Time: 3 Hours General Instructions: Read the following instructions carefully. a) There are 33 questions in this question paper. All questions are compulsory. b) Section A: Q. No. 1 to 16 are objective type questions. Q. No. 1 and 2 are passage based questions carrying 4 marks each while Q. No. 3 to 16 carry 1 mark each. c) Section B: Q. No. 17 to 25 are short answer questions and carry 2 marks each. d) Section C: Q. No. 26 to 30 are short answer questions and carry 3 marks each. e) Section D: Q. No. 31 to 33 are long answer questions carrying 5 marks each. f) There is no overall choice. However, internal choices have been provided. g) Use of calculators and log tables is not permitted.

Section : A Read the given passage and answer the questions that follow: Periodic properties show a regular gradation on moving from left to right in a period or from top to bottom in a group. Down a group, the atomic/ionic radii, metallic character and reducing character increase while ionization enthalpy and electronegativity decrease. Along a period from left to right, atomic/ionic radii and metallic character decrease while ionization enthalpy, electronegativity, non-metallic character and oxidising power increase. However, electron gain enthalpy becomes less negative down a group but more negative along a period. In contrast, inert gases have positive electron gain enthalpies which do not show any regular trend. The following questions are multiple choice questions. Choose the most appropriate answer: (i). Among the elements B, C, N, F and Si, the correct order of their non-metallic character is:

a) F> N> C> B> Si.

b) F> B> C> N> Si.

c) Si> N> C> B> F.

d) N> F> C> B> Si.

(ii). In which one of the following the first ion has a larger size than the second?

a) Mg+2, Na+

b) Na+, Mg+2

c) Na+, K+

d) Li+,Na+

OR

Which of the following halogens has the highest electron affinity?

a) F b) Cl c) Br d) I

(iii). Which among the following ions is the smallest?

a) S2-

b) Cl-

c) Na+

d) Mg2+

(iv). The property which does not reflect periodicity in elements is

a) electronegativity b) electron affinity c) neutron proton ratio d) ionisation energy

2. Read the passage given below and answer the following questions: Hybridization is defined as the concept of mixing two atomic orbitals with the same energy levels to give a degenerated new type of orbitals. This intermixing is based on quantum mechanics. The atomic orbitals of the same energy level can only take part in hybridization and both fully filled and half-filled orbitals can also take part in this process, provided they have equal energy. During the process of hybridization, the atomic orbitals of similar energy are mixed together such as the mixing of two ‘s’ orbitals or two ‘p’ orbitals or mixing of an ‘s’

orbital with a ‘p’ orbital or ‘s’ orbital with a ‘d’ orbital. Based on the types of orbitals involved in mixing, the hybridization can be classified as sp3, sp2, sp, sp3d, sp3d2, sp3d3.

In these questions Q. No i-iv , a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.

a) Assertion and reason both are correct statements and reason is correct explanation for assertion.

b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.

c) Assertion is the correct statement but reason is wrong statement.

d) Assertion is wrong statement but reason is correct statement.

(i) Assertion: Sulphur in SO2 is sp2 hybridised. Reason: SO2

has a planar shape. (ii) Assertion: Molecules having different hybridisation can have the same shape. Reason: Shape of the molecule depends on the repulsions between bond pairs and lone pairs. (iii) Assertion:NO3− is planar while NH3 is pyramidal. Reason: N in NH3 is sp3 hybridised whereas N in NO3− is sp2 hybridised. (iv) Assertion: Carbon dioxide has a linear geometry. Reason: Hybridisation of C in carbon dioxide is sp2

OR Assertion: The central atom of both NH3 and H2O are sp3 hybridised but H-N-H bond angle is greater than H-O-H bond angle. Reason: Nitrogen atom has one lone pair whereas oxygen atom has two lone pairs.

Questions 3 to 11 are multiple choice questions:

3. The mass of a photon of sodium light with wavelength 5890 Å is

(a) 7.352 × 10-32 g (b) 7.352 × 10-33 g (c) 3.752 × 10-33 g

(d) 3.752 × 10-32 g 4. On excessive heating with oxygen, lithium forms

(a) LiO (b) LiO2

(c) Li2O (d) Li2O2

OR The higher reactivity of Na in water in comparison to Li is because of the

(a) high boiling point of Na (b) high melting point of Na (c) low boiling point of Na (d) low melting point of Na

5. Which of the following is not a state function? (a) Internal energy (b) Work (c) Free energy (d) Enthalpy

6. Which of the following molecules is paramagnetic? (a) H2 (b) O2 (c) Li2 (d) C2

OR How many electrons are required by the nitrogen atom to complete its octet?

(a) 1 (b) 2 (c) 3 (d) 4

7. In which of the following reaction, there is no change in oxidation number: (a) SO2 + 2H2S → 2H2O + 3S (b) 2Na + O2→ Na2O2

(c) Na2O + H2SO4→ Na2SO4 + H2O (d) 4KClO3→ 3KClO4 + KCl

OR

Which of the following reactions is not a redox reaction?

(a) NH4Cl + KOH → NH3 + H2O +KCl (b) 2Rb + H2O → 2RbOH + H2 (c) Zn + 2AgCN → 2Ag + Zn(CN)2 (d) 2CuI2→ 2CuI + I2

8. The correct representation of the Charles’s Law is given in

(a)

(b)

(c)

(d)

OR

Dipole-dipole forces are present between which pair of molecules?

(a) Cl2 and Cl2 (b) H2 and Cl2 (c) HCl and Cl2 (d) HCl and HCl

9.The C − O bond order in ion is a) 1.33 b) 2.33 c) 1.53 d) 2.53

10.Which of the following gaseous reactions is favoured by low pressure?

a)

b)

c)

d)

11. Which of the following carbocations is the most stable?

a) F3C−CH2+

b) (CH3)2 CH+

c) CH3+ d) CF3+

In the following questions (Q. No. 12 - 16) a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.:

(A) Both assertion and reason are correct statements, and reason is the correct explanation of the assertion.

(B) Both assertion and reason are correct statements, but reason is not the correct explanation of the assertion.

(C) Assertion is correct, but reason is wrong statement.

(D) Assertion is wrong, but reason is the correct statement.

12. Assertion: Antimony is a metalloid.

Reason: Sb shows metallic character.

13. Assertion: Chlorobenzene undergoes Friedel craft alkylation at the para position.

Reason: Halobenzenes are activating groups.

14. Assertion: F-F bond in F2 is stronger than Cl-Cl bond in Cl2.

Reason: Cl is larger in size.

OR

Assertion: AsF5 is known but NF5 is not known.

Reason: Arsenic has lower electronegativity than Nitrogen.

15. Assertion: Sigma bond is weak while Pi bond is strong.

Reason: Atoms rotate freely about sigma bonds.

16. Assertion: Density and Pressure are intensive properties.

Reason: Intensive properties are independent of the amount of substance.

Section : B

17. Write down the general valence shell electronic configuration and group valency

of the boron and the carbon families.

OR

Why does elemental silicon not form graphite like structure as carbon does?

18. What is the difference between the covalent radius and the van der Waals'

radius?

19. For the given reaction, calculate the total change in entropy at 25°C.

It is given that ΔH = + 24.2 kJ mol−1 and

ΔS = 228.4 JK−1 mol−1.

OR

What is the difference between a closed and an isolated system?

20.What do you understand by Aufbau principle?

OR

Explain the hybridisation in methane molecule.

21. Give the IUPAC name of the following compound.

22. How many moles are present in 5.12 × 1024 molecules of chlorine?

23. What are the main causes for permanent and temporary hardness of water?

24. Why do boron and silicon have almost the same values of electronegativity?

25. Determine the change in oxidation number of nitrogen in the given reaction.

Section : C

26. What would be the new volume of gas if the pressure of the gas is doubled?

OR

(i)Two containers A and B have the same gas. The pressure, volume and temperature of container A are twice that of container B. What is the ratio of the number of molecules of A and B?

(ii) State Gay Lussac’s law.

27. For a reaction , the concentration of Cu2+ is

2.1 × 10−3 mol L−1 and that of . Predict whether this system is at equilibrium or not if the equilibrium constant at 298 K is 5 × 1015.

OR

a) State the law of chemical equilibrium and what is equilibrium constant?

b) Is the value of the equilibrium constant the same for the forward and the reverse reaction? How can the value of equilibrium constant be used to predict the extent of a reaction?

28. (i) What are the signs of ΔH and ΔS for the following reaction?

2H(g)→H2(g)

(ii) What is lattice enthalpy?

29. Comment on the use of dihydrogen as a fuel.

30. Explain disproportionation reaction with example.

Section : D

31. (a) What is a diagonal relationship?

(b) Write down the properties of carbon and phosphorus, which indicate the diagonal relationship between them.

OR

Describe the general trends in the following properties of the elements in group 13 and 14.

(i) Atomic size

(ii) Ionisation enthalpy

(iii) Metallic character

(iv) Oxidation states

(v) Nature of halides

32. Convert the following:

(a) 1,1-Dibromopropane to 3-Hexanol

(b) 1,2-Dibromoethane to Ethanol

(c) Ethanol to Methanal

(d) Acetylene to Biphenyl

(e) Propene to Cumene

OR

Complete the following reactions:

(d)

(e)

33. (a) Describe nucleophiles in detail.

(b) Which of the following molecules are considered as nucleophiles

NH3,CO, AlCl3 and BH3.

OR

(a) What is the Resonance effect? (b) Explain the following effects with examples:

(i) +R effect

(ii) −R effect

Mock Test Chemistry

Solutions

1.(i)

In a period, the non-metallic character increases from left to right. Within a group,

non-metallic character decreases from top to bottom. Therefore, the correct sequence of

decreasing non-metallic character is F> N> C> B> Si.

Hence, the correct answer is option A.

(ii). Na+ and Mg2+ are isoelectronic cations. Therefore, due to the lower effective nuclear

charge, the ionic radius of Na+ is higher than that of Mg2+.

Hence, the correct answer is option B.

OR

Although fluorine is the most electronegative element among halogens, yet it does not

have the highest electron affinity. This is due to its small size.

Hence, the correct answer is option b.

(iii). In S2− and Cl−, electrons are being added to the valence shell. This decreases the attraction between the nucleus and the valence electrons. Consequently the ionic radius increases. However, in case of Na+ and Mg2+ electrons are being removed from the valence shells, so the attraction between the electrons and the nucleus is more. So, their size decreases. Mg2+ is doubly charged.

So, there is more attraction of electrons by the nucleus. This makes it smaller than Na+.

Hence, the correct answer is option D.

(iv). Neutron proton ratio does not reflect the periodicity of elements. Hence, the correct answer is option C.

2. (i) (ii).

The sulphur in SO2 has 6 electrons in its valence shell. It forms two double bonds with

two oxygens and one lone pair of electrons is available on the atom. Now, on counting

electron groups around the S, there are 2 sigma bonds and one lone pair i.e. 3 electron

pairs that tells about the hybridisation of the atom. Hence, S is sp2 hybridised.

SO2 has trigonal planar geometry , and has bent or V-shape.

Therefore, the assertion is correct but reason is incorrect.

Hence, the correct answer is option C.

Shape of the molecule is determined by the repulsions between lone pairs and bond pairs.

Two molecules having the same shape can have different hybridisations.

For example: NO2+ and I3- have different hybridisation but same shape i.e. linear.

Therefore, assertion and reason are correct statements and reason is the correct

explanation for assertion.


(iii).

In NO3- there are 3 sigma bonds between N and O. This implies that hybridisation of N

in NO3- is sp 2 and geometry is trigonal planar.

In NH3 there are 3 sigma bonds and 1 lone pair of electrons. This implies that

hybridisation of N in NH3 is sp3 and geometry is tetrahedral.

Therefore, assertion and reason are correct and reason is the correct explanation for

assertion.


(iv).

The carbon in carbon dioxide forms double bonds with two oxygen atoms and is sp hybridised. The geometry of a CO2 molecule is linear. Therefore, the assertion is correct but reason is a wrong statement. Hence, the correct answer is option C. OR Due to the presence of two lone pairs on oxygen atom, lone pair lone pair repulsions exist in addition to lone pair bond pair repulsions and hence, bond angle in H-O-H is less than the H-N-H bond angle due to greater repulsions. Therefore, both assertion and reason are correct and reason is the correct explanation for assertion. Hence, the correct answer is option A.

3. Wavelength is related to mass as follows:


4. Lithium forms normal oxide Li2O as shown in the following reaction:

4Li + O2 → 2Li2O


OR

The reaction of sodium with water is exothermic and helps in the melting of sodium. As

sodium melts, more molecules are available to react with water. Thus, this cycle

continues and the reaction results in an explosion. The melting point of lithium is higher

than that of sodium. Hence, it does not melt when kept in water and reacts rather gently.


5. State functions are those which do not depend upon the path followed. Work depends on

the path followed.


6. A molecule is said to be paramagnetic if one or more of its molecular orbitals is

singly-occupied. If all the molecular orbitals in a molecule are doubly-occupied, then it is

said to be diamagnetic.

An oxygen atom has a total of 8 electrons. Therefore, there are 16 electrons in an O2

molecule. The electronic configuration of O2 molecule is written as

Therefore, an O2 molecule is paramagnetic.


OR

The valence shell of a nitrogen atom contains five electrons. Therefore, it requires three

more electrons to complete its octet.


7. In the reaction Na2O + H2SO4→ Na2SO4 + H2O, the oxidation states of Na, O, H and S

are same in both; reactant and product sides, hence there is no change in oxidation

number


OR

NH4Cl + KOH → NH3 + H2O +KCl

The oxidation states of all of the elements in this reaction are the same in the reactant and

the product side. Hence, in the reaction, no element is going to reduce and oxidize, so it

is not a redox reaction.


8.

According to Charle's Law, the volume of a given mass of gas is directly proportional to

its absolute temperature, keeping the pressure constant.

V1T1 = V2T2 = k at constant pressure

9.


OR

Dipole-dipole forces exist between molecules having permanent dipole moments. An

HCl molecule possesses permanent dipole moment. Therefore, dipole-dipole force exists

between two HCl molecules. Dipole-dipole interaction between two HCl molecules is

shown in the given figure.


Resonating structures of ion is


10. 11. 12. 13.

In the equation ,the forward reaction is accompanied by an

increase in the number of moles and number of moles directly proportional to pressure.

Hence, according to Le Chatelier’s principle, it is favoured by low pressure.


Carbocations are stabilised by electron-releasing (+I) groups and destabilised by

electron-withdrawing (−I) groups. Hence, among the given carbocations, (CH3)2 CH+ is

the most stable.


Antimony(Sb) is a metalloid because it shows characters of both metal and nonmetal.

Hence, the reason is false.


Chlorobenzene undergoes Friedel craft alkylation at the para position due to resonance,

where the electron density on o- and p- positions is greater than that at the meta position.

Due to -I effect, halobenzenes are deactivating in nature. The reason is a wrong

statement.


14. The bond dissociation energy of:

F-F: 156.9 kJ/mol

Cl-Cl: 242.58 kJ/mol

In F-F many electrons are concentrated over two small nuclei and are separated over a

very small distance, hence they repel each other so the energy required is less.

The statement in reason is correct but it is not the correct explanation of the assertion.


OR

AsF5 is known but NF5 is not known because N does not have an accessible d-orbital.

Also, the reason, Arsenic has lower electronegativity than Nitrogen is true but it is not

the correct explanation of the assertion.


15. Sigma bonds are stronger than Pi bonds due to more overlap of spherical orbitals. Also,

atoms can rotate freely about a sigma bond. But the reason is not the correct explanation

for the assertion.

Assertion is wrong, but the reason is the correct statement.


16. Density and Pressure are intensive properties because they are independent of the

amount of substance.


17. Boron family:

Electronic configuration: ns2 np1

Group valency : +3

Carbon family:

Electronic configuration: ns2 np2

Group valency : +4

OR

Elemental silicon does not form graphite like structure owing to its reluctance to form pπ

− pπ multiple bonds. This reluctance is because of the larger size of the silicon atom.

Hence, silicon exists only in diamond-like structure.

18.

19. Using the relation,

ΔStotal = ΔSsys + ΔSsurr

Hence, the total change in entropy is 147.2 JK-1 mol-1.

OR

In a closed system, there is no exchange of matter; however, exchange of energy is

possible between the system and the surroundings. On the other hand, neither energy nor

matter is exchanged between the system and surroundings in an isolated system.

Covalent Radius Vander Waals Radius

It is the radius of an atom’s core that is in contact with the core of an atom in a bonded situation.

It is the overall size of the atom that includes its valence shell in a non-bonded situation.

20. Aufbau principle states that in the ground state of atoms, the orbitals are filled in the

order of their increasing energies.

It means that an orbital with higher energy will get filled only if all the orbitals of lesser

energy are completely filled. Hence, the filling of the 2s orbital will start only after the 1s

orbital is completely filled. The order in which the filling of electrons takes place in the

various orbitals is 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p, and so on.

OR

Carbon (in-ground state): 1s2 2s2 2p2

2s 2p

Carbon (in an excited state): 1s2 2s1 2p3

2s 2p

Hence, we can see that in an excited state, carbon contains 4 valence electrons.

The molecular formula of methane is CH4. Thus, carbon has to make 4 equivalent sigma

bonds with 4 atoms of hydrogen. As a result, the 2s and 2p-orbitals of carbon undergo

hybridisation to give 4 equivalent sp3 hybrid orbitals. These four orbitals direct

themselves at the maximum distance from each other, thereby giving rise to a

tetrahedron structure.

21.

3,3-diethylpentane

22. 1 mole of chlorine is equivalent to 6.022 × 1023 molecules of chlorine.

Hence, 5.12 × 1024 molecules of chlorine will be present in

Thus, 8.5 mole of chlorine contains 5.12 × 1024 molecules of chlorine.

23. 24. 25.

a. The main cause for permanent hardness is the presence of soluble salts of magnesium

and calcium salts as chlorides and sulphates, and the main cause for temporary hardness

is the presence of calcium and magnesium hydrogen carbonates.

b. Mg (HCO3)2 is converted to Mg (OH)2 and not to MgCO3 because the solubility

product of Mg(OH)2 is greater than MgCO3. Therefore, Mg(OH)2 gets precipitated.

Boron belongs to the 13th group and 2nd period of the modern periodic table while silicon

belongs to the 14th group and 3rd period. On moving from left to right in a period,

electronegativity increases and while moving down the group, electronegativity

decreases. Therefore, on moving diagonally electronegativity remains almost the same.

The oxidation number of nitrogen in is +5.

And, the oxidation number of nitrogen in is − 3.

Hence, the change in oxidation number of nitrogen is from +5 to −3.

26.

Initial pressure, pi = p

Final pressure, pf = 2p

Initial volume Vi = V

Final volume Vf =?

According to Boyle’s law:

p1V1 = p2V2

If the pressure of the gas is doubled, then the volume will be halved.

OR

(i)Using the relation

Hence, the ratio of the number of molecules of A and B is found to be 2:1.

27.

(ii) Gay Lussac’s law states that, ‘at constant volume, the pressure of a fixed amount of

a gas is directly proportional to the temperature’.

Kc = 5 x 1015 (given)

In order to predict whether the given system is at equilibrium or not, we need to calculate

the concentration quotient Qc.

Since the value of Qc is more than that of an equilibrium constant, so the reaction will

proceed to the backward direction and is not in equilibrium.

OR

a) The law of chemical equilibrium states that at a given temperature, the product of

concentrations of the reaction products raised to the respective stoichiometric

coefficients in the balanced chemical equation divided by the product of the

concentrations of the reactants raised to the respective stoichiometric coefficients has a

constant value. This constant value is the equilibrium constant for the reaction.

For a general reaction

aA + bB → cC + dD

the equilibrium constant is represented as

where [A], [B], [C], and [D] is the equilibrium concentration of the reactants and the

products.

b) The value of equilibrium constant for the forward reaction is not equal to the value of

equilibrium constant for the backward or reverse reaction. In fact, the value of

equilibrium constant for the backward reaction is the inverse of the value of equilibrium

constant for the forward reaction.

The numerical value of the equilibrium constant for a reaction helps in predicting the

28. 29. .

extent of a reaction.

● If the value of equilibrium constant for a reaction is larger than 103, then the

reaction will proceed towards completion and the products predominate the

reactants.

● If the value of equilibrium constant for a reaction is smaller than 10-3, then the

reaction will hardly proceed and the reactants predominate the products.

● If the value of the equilibrium constant for a reaction is between 103 to 10-3, then

appreciable concentrations of reactants, as well as the products, will be present at

equilibrium.

(i) The given reaction represents the formation of bonds. Since energy is released during

the formation of bonds, the sign of ΔH is negative. Moreover, atoms combine to form a

molecule, i.e. a more ordered arrangement is formed. Thus, signs of ΔS would also be

negative.

(ii) Lattice enthalpy is the enthalpy change that occurs when one mole of an ionic

compound dissociates into its ions in gaseous state.

Example:

Hydrogen has many advantages as a fuel. It produces a greater amount of energy than

other fuels such as diesel, petrol, CNG. It is a clean fuel as it does not produce gases that

cause pollution (like carbon monoxide, carbon dioxide, sulphur dioxide etc). It produces

30.

water on combustion with only traces of nitrogen oxide.

Its uses are:

(1) It is used as a rocket fuel in space research.

(2) It is used in fuel cells (type of galvanic cells). The energy produced on its combustion

is used to generate electricity.

(3) It is also being used as an alternative fuel in some motor vehicles. However, this is

not very common since hydrogen is highly flammable.

Disproportionation reaction is a special type of redox reaction. In a disproportionation

reaction an element in one oxidation state is simultaneously oxidised and reduced. One

of the reacting substances in a disproportionation reaction always contains an element

that can exist in at least three oxidation states. The element in the form of a reacting

substance is in the intermediate oxidation state; both higher and lower oxidation states of

that element are formed in the reaction.

For example:

4H3PO3 → 3H3PO4 + PH3

On heating, it undergoes a disproportionation reaction to give ortho phosphoric acid and

phosphine.

In this reaction:

Oxidation half reaction: H3PO3→ H3PO4

31.

Reduction half reaction: H3PO3 → PH3

(a) Diagonal relationship is found in the periodic table between the elements of period 2

and 3. According to this, the elements of the second period have similar properties with

the diagonally placed elements of period 3. This property is due to the similarities in size

and even electronegativity as the atomic size increases down the group but decreases in a

period. Thus, diagonally placed elements possess nearly the same size and

electronegative character.

For example, lithium shows a diagonal relationship with magnesium.

(b) Following are some points that indicate the diagonal relationship between carbon and

phosphorus:

(1) Both show allotropy.

(2) The electronegativity of carbon is 2.544, while that of phosphorus is 2.253 (on

Pauling scale).

(3) Like carbon, phosphorus forms strong σ and π bonds to other members of its row.

(4) Many organophosphorus compounds behave like corresponding hydrocarbons.

(5) Like the cyclopentadienyl ion (C5H5-), a similar anion of phosphorus called

pentaphosphate cyclopentadienyl (P5-) is known, which can coordinate to central metal

atom in transition metal complexes through all 5 atoms.

OR

Property Group 13 Group 14

32.

(a)

(i) Atomic size With the exception of gallium, the atomic size increases from boron to thallium.

Atomic size increases gradually from carbon to lead.

(ii) Ionisation enthalpy A regular decreasing trend is not observed in first ionisation enthalpy.

First ionisation enthalpy decreases from carbon to tin.

(iii) Metallic character Metallic nature increases from boron to aluminium, then decreases from aluminium to thallium.

Increases gradually on moving down the group.

(iv) Oxidation state +3 and +1 oxidation states the stability of +1 increases while that of +3 decreases on moving down the group.

+4 and +2 oxidation states the stability of +2 increases while that of +4 decreases on moving down the group

(v) Nature of Halides All form trihalides of the type MX3 the stability decreases from boron to thallium. Thallium also forms stable TlCl.

All form tetrahalides of the type MX4. Stability

decreases. Ge, Sn and

Pb also form dihalides,

MX2 stability increases.

(b)

(c)

(d)

(e)

33.

OR

(d)

(e)

(a) Nucleophiles are nucleus seeking or electron rich in nature. They attract positively charged species or attack at the positive end of the molecule.

● They can be neutral or anionic.

● Neutral- NH3, H2O (both have lone pair of e- which can be donated) ● Anionic − CN-, OH-, Cl- etc. (have excess electrons so e- rich). ● Nucleophile is a free species. ● Strength of the nucleophile does not depend on any other molecule or atom; it is

the property of its own. (b) NH3 and CO are nucleophiles as they both have lone pairs of electrons over an O

atom.

OR

(a) Resonance effect is defined as the ‘polarity produced in the molecule by the interaction of two π-bonds or between a π-bond and lone pair of electrons present on an adjacent atom’. In simple terms, it can be defined as the delocalisation of π-electrons due to the presence of an electron releasing or electron withdrawing substituent, which results in canonical forms with different electron distribution.It is designated as the R or M effect. Now, a resonance effect can be either positive or negative.

(b)

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