Assertion (A) : Acetylation of aniline gives a monosubstituted product.
Reason (R) : Activating effect of –NHCOCH3 group is more than that of amino group.
Correct answer: (c)
Question 17
Assertion (A) : The molecularity of the reaction H2 + Br2 → 2HBr appears to be 2.
Reason (R) : Two molecules of the reactants are involved in the given elementary reaction.
Correct answer: (c)
Question 18
Assertion (A) : Low-spin tetrahedral complexes are rarely observed.
Reason (R) : Crystal field splitting energy is less than pairing energy for tetrahedral complexes.
Correct answer: (a)
Very short answer type Questions
Question 19
What is Henry’s law ? Give one application of it.
Henry’s law states that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid. Application: Used in deep-sea diving to prevent bends.
Question 20
On diluting two electrolytes A and B, the Λm of A increases 25 times while that of B increases by 1.5 times. Which electrolyte is strong ? Justify graphically.
Electrolyte B is strong because its molar conductivity increases only slightly on dilution, showing it is almost completely ionized.
Question 21
Complete the following equations :
(a) 2MnO4− + 5NO2− + 6H+ →
(b) Cr2O72− + 14H+ + 6e− →
(a) 2MnO4− + 5NO2− + 6H+ → 2Mn2+ + 5NO3− + 3H2O
(b) Cr2O72− + 14H+ + 6e− → 2Cr3+ + 7H2O
Question 22
Identify ‘A’ and ‘B’ in the following reactions.
(a) A = 2-Chloropropane, B = Isopropyl cyanide
(b) A = Propene, B = 1-Bromopropane
Question 23
Account for the following :
(i) Phenol is more acidic due to resonance stabilization of phenoxide ion.
(ii) Branching reduces surface area, decreasing intermolecular forces and boiling point.
Question 24
Explain briefly :
(a) Carbylamine reaction
(b) Gabriel phthalimide synthesis
(a) Primary amines give isocyanides on heating with CHCl3 and KOH.
(b) Used for preparation of primary amines from alkyl halides.
Question 25
(a) Write chemical reaction to show that open structure of D-glucose contains the straight chain.
(b) What type of linkage is responsible for the formation of protein ?
(a) Oxidation of glucose with Br2 water forms gluconic acid.
(b) Peptide linkage.
Short answer type Questions
Question 26
(a) Differentiate between Ideal solution and Non-ideal solution.
(b) 30 g of urea is dissolved in 846 g of water. Calculate the vapour pressure
of water for this solution if vapour pressure of pure water at 298 K is
23.8 mm Hg.
(a) Difference:
Ideal Solution
Non-ideal Solution
Obeys Raoult’s law at all concentrations
Does not obey Raoult’s law
ΔHmix = 0, ΔVmix = 0
ΔHmix ≠ 0, ΔVmix ≠ 0
(b) Calculation:
Moles of urea = 30 / 60 = 0.5 mol
Moles of water = 846 / 18 = 47 mol
Mole fraction of water = 47 / (47 + 0.5) = 0.9895
(b) Starch has α-glycosidic linkage, cellulose has β-glycosidic linkage.
Case-based Questions
Question 31
The rate of reaction is concerned with decrease in concentration of reactants or
increase in the concentration of products per unit time. It can be expressed as
instantaneous rate at a particular instant of time and average rate over a large
interval of time. Mathematical representation of rate of reaction is given by rate
law. Rate constant and order of a reaction can be determined from rate law or its
integrated rate equation.
(i) What is average rate of reaction?
(ii) Write two factors that affect the rate of reaction.
(iii) (1) What happens to rate of reaction for zero order reaction?
(2) What is the unit of k for zero order reaction?
OR
(iii) (1) For a reaction P + 2Q → Products,
Rate = k[P]1/2[Q]1. What is the order of the reaction?
(2) Define pseudo first order reaction with an example.
(i) Average rate of reaction:
Average rate of reaction is defined as the change in concentration of reactants
or products per unit time over a given time interval.
Mathematically,
Rate = Δ[Concentration] / Δt
(ii) Factors affecting rate of reaction:
Two factors that affect the rate of reaction are:
• Concentration of reactants – Higher concentration increases collision frequency.
• Temperature – Increase in temperature increases kinetic energy of molecules.
(iii) (1) Zero order reaction:
In a zero order reaction, the rate of reaction is independent of the concentration
of reactants and remains constant throughout the reaction.
(iii) (2) Unit of rate constant (k):
For zero order reaction,
Rate = k
Unit of k = mol L-1 s-1
OR
(iii) (1) For a reaction P + 2Q → Products,
Rate = k[P]1/2[Q]1
Order of reaction:
Order = 1/2 + 1 = 3/2
(iii) (2) Pseudo first order reaction:
A reaction which is actually of higher order but behaves as first order due to
excess concentration of one reactant is called pseudo first order reaction.
Example: Hydrolysis of ethyl acetate in excess water.
Question 32
In coordination compounds, metals show two types of linkages, primary and
secondary. Primary valencies are ionisable and are satisfied by negatively charged
ions. Secondary valencies are non-ionisable and are satisfied by neutral or negative
ions having lone pair of electrons. Primary valencies are non-directional while
secondary valencies decide the shape of the complexes.
(i) If PtCl2.2NH3 does not react with AgNO3, what will be its formula?
(ii) What is the secondary valency of [Co(en)3]3+?
(iii) (1) Write the formula of Iron(III)hexacyanidoferrate(II).
(2) Write the IUPAC name of [Co(NH3)5Cl]Cl2.
OR
(iii) Write the hybridization and magnetic behaviour of
[Ni(CN)4]2−.
(i) Since the compound does not react with AgNO3, chloride ions are
not present outside the coordination sphere.
Therefore, both Cl− ions are coordinated to Pt.
Formula: [Pt(NH3)2Cl2]
(ii) In [Co(en)3]3+, three ethylenediamine molecules act as
bidentate ligands.
Total donor atoms = 3 × 2 = 6
Hence, secondary valency = 6
(iii) (1) Iron(III)hexacyanidoferrate(II) is formed by Fe3+ and
[Fe(CN)6]4−.
Formula: Fe4[Fe(CN)6]3
(iii) (2) In [Co(NH3)5Cl]Cl2, the coordination sphere
contains one chloride ligand.
IUPAC name: Pentaamminechloridocobalt(III) chloride
OR
(iii) For [Ni(CN)4]2− :
Ni2+ has electronic configuration 3d8.
CN− is a strong field ligand causing pairing of electrons.
Hybridisation = dsp2
The complex is square planar and diamagnetic.
Long answer type Questions
Question 33
(a) (i) State Kohlrausch’s law of independent migration of ions.
Write an expression for the limiting molar conductivity of acetic acid
according to Kohlrausch’s law.
(ii) Calculate the maximum work and log Kc for the given reaction
at 298 K :
Ni (s) + 2Ag+ (aq) ⇌ Ni2+ (aq) + 2Ag (s)
Given :
E°Ni2+/Ni = −0.25 V ,
E°Ag+/Ag = +0.80 V
1 F = 96500 C mol−1
OR
(b) (i) State Faraday’s first law of electrolysis. How much charge,
in terms of Faraday, is required for the reduction of 1 mol Cu2+ to Cu?
(ii) Calculate emf of the following cell at 298 K :
Mg (s) | Mg2+ (0.1 M) || Cu2+ (0.01 M) | Cu (s)
Given : E°cell = +2.71 V , 1 F = 96500 C mol−1, log 10 = 1
(a) (i) Kohlrausch’s law:
At infinite dilution, each ion contributes independently to the molar
conductivity of an electrolyte, irrespective of the nature of the other ion.
(b) (i) Faraday’s first law:
The mass of a substance deposited or liberated at an electrode is directly
proportional to the quantity of electricity passed.
Cu2+ + 2e− → Cu
Charge required = 2 Faraday
(ii) Cell emf:
E = E° − (0.0591 / n) log Q
Q = 0.1 / 0.01 = 10
E = 2.71 − (0.0591 / 2) × 1
= 2.68 V
Question 34
Assign reason for each of the following :
(i) Manganese exhibits the highest oxidation state of +7 among the 3d series of
transition elements.
(ii) Transition metals and their compounds are generally found to be good
catalysts in chemical reactions.
(iii) Cr2+ is reducing in nature while with the same d-orbital
configuration (d4) Mn3+ is an oxidising agent.
(iv) Zn has lowest enthalpy of atomization.
(v) Cu+ is unstable in an aqueous solution.
(i) Manganese has the maximum number of unpaired electrons and can use
both 3d and 4s electrons for bonding, hence shows +7 oxidation state.
(ii) Transition metals show variable oxidation states and can form
intermediate complexes, lowering activation energy of reactions.
(iii) Cr2+ tends to get oxidised to more stable Cr3+,
therefore acts as a reducing agent, while Mn3+ tends to get reduced to
Mn2+, hence acts as an oxidising agent.
(iv) Zinc has completely filled d10 configuration and weak
metal–metal bonding, resulting in low enthalpy of atomization.
(v) Cu+ undergoes disproportionation in aqueous solution:
2Cu+ → Cu2+ + Cu
Question 35
(a) (i) Carry out the following conversions :
(1) Ethanal to But-2-en-1-al
(2) Propanoic acid to 2-chloropropanoic acid
(ii) An alkene with molecular formula C5H10 on ozonolysis gives
a mixture of two compounds ‘B’ and ‘C’. Compound ‘B’ gives positive Fehling test
and also reacts with iodine and NaOH solution. Compound ‘C’ does not give
Fehling solution test but forms iodoform. Identify the compounds ‘A’, ‘B’ and ‘C’.
OR
(b) (i) Distinguish with a suitable chemical test :
(1) CH3COCH2CH3 and CH3CH2CH2CHO
(2) Ethanal and Ethanoic acid
(ii) Write the structure of oxime of acetone.
(iii) Identify A to D :
CH3COOH
—PCl5→ A
—H2/Pd–BaSO4→ B
B
—(i) CH3/MgBr
(ii) H3O+→ C
B —LiAlH4→ D
(a) (i) (1) Ethanal to But-2-en-1-al:
Ethanal undergoes aldol condensation followed by dehydration.
(ii) Identification:
Compound B gives Fehling test and iodoform test, hence it is ethanal
(CH3CHO).
Compound C gives iodoform test but not Fehling test, hence it is propanone
(CH3COCH3).
The alkene which on ozonolysis gives ethanal and propanone is:
Compound A: 2-Methylbut-2-ene
OR
(b) (i) (1) CH3COCH2CH3 and CH3CH2CH2CHO:
Use Fehling’s test.
CH3CH2CH2CHO gives red precipitate,
while CH3COCH2CH3 does not react.
(i) (2) Ethanal and Ethanoic acid:
Use sodium bicarbonate test.
Ethanoic acid gives brisk effervescence of CO2,
while ethanal does not react.
(ii) Oxime of acetone:
CH3–C(=NOH)–CH3
(iii) Identification of A to D:
A = CH3COCl (Acetyl chloride)
B = CH3CHO (Ethanal)
C = (CH3)2CHOH (Propan-2-ol)
D = CH3CH2OH (Ethanol)
Multiple Choice type Questions
Question 1
The conversion of an alkyl halide into an alkene by alcoholic KOH is classified as
(a) a substitution reaction
(b) an addition reaction
(c) a dehydrohalogenation reaction
(d) a dehydration reaction
Correct Answer: (c) a dehydrohalogenation reaction
Question 2
The oxidation state of Fe in [Fe(CO)5] is
(a) +2
(b) 0
(c) +3
(d) +5
Correct Answer: (b) 0
Question 3
Among the following, which is the strongest base?
(a) Aniline
(b) p-Toluidine
(c) Benzylamine
(d) p-Nitroaniline
Correct Answer: (c) Benzylamine
Question 4
The slope in the plot of ln[R] vs. time for a first order reaction is
(a) +k/2.303
(b) −k
(c) −k/2.303
(d) +k
Correct Answer: (b) −k
Question 5
An α-helix is a structural feature of
(a) Sucrose
(b) Polypeptides
(c) Nucleotides
(d) Starch
Correct Answer: (b) Polypeptides
Question 6
Racemisation occurs in
(a) SN1 reaction
(b) SN2 reaction
(c) Neither SN1 nor SN2 reaction
(d) SN2 reaction as well as SN1 reaction
Correct Answer: (a) SN1 reaction
Question 7
Value of Henry’s constant KH
(a) increases with decrease in temperature
(b) decreases with increase in temperature
(c) increases with increase in temperature
(d) remains constant
Correct Answer: (c) increases with increase in temperature
Question 8
Which of the following solutions of KCl will have the highest value of molar conductivity?
(a) 0.01 M
(b) 1 M
(c) 0.5 M
(d) 0.1 M
Correct Answer: (a) 0.01 M
Question 9
Which of the following reactions are feasible?
(a) CH3CH2Br + Na+ −O-C(CH3)3 → ether
(b) (CH3)3C-Cl + Na+ −O-CH2CH3 → ether
(c) Both (a) and (b)
(d) Neither (a) nor (b)
Correct Answer: (a) Reason: Williamson synthesis works best with primary halides.
Question 10
Which of the following is most reactive in nucleophilic addition reactions?
(a) HCHO
(b) CH3CHO
(c) CH3COCH3
(d) CH3COC2H5
Correct Answer: (a) HCHO
Question 11
Which of the following does not give aldol condensation reaction?
(a) CH3CHO
(b) Cyclohexanecarbaldehyde
(c) Benzaldehyde
(d) CH3COCH3
Correct Answer: (c) Benzaldehyde
Question 12
For the reaction 3A → 2B, rate of reaction + d[B]/dt is equal to
(a) −3/2 d[A]/dt
(b) −2/3 d[A]/dt
(c) −1/3 d[A]/dt
(d) +2 d[A]/dt
Correct Answer: (b) −2/3 d[A]/dt
Question 13
Which of the following characteristics of transition metals is associated with their catalytic activity?
(a) Paramagnetic nature
(b) Colour of hydrated ions
(c) High enthalpy of atomisation
(d) Variable oxidation states
Correct Answer: (d) Variable oxidation states
Question 14
The formula of the complex dichloridobis (ethane-1,2-diamine) platinum (IV) nitrate is
(a) [PtCl2(en)2(NO3)2]
(b) [PtCl2(en)2](NO3)2
(c) [PtCl2(en)2(NO3)]NO3
(d) [Pt(en)2(NO3)2]Cl2
Correct Answer: (b) [PtCl2(en)2](NO3)2
Assertion–Reason type Questions
Question 15
Assertion (A): Osmotic pressure is a colligative property.
Reason (R): Osmotic pressure is proportional to the molality.
Correct Answer: (c) (A) is true, but (R) is false.
Question 16
Assertion (A): Conductivity decreases with decrease in concentration of electrolyte.
Reason (R): Number of ions per unit volume that carry the current in a solution
decreases on dilution.
Correct Answer: (a) Both (A) and (R) are true and (R) is the correct explanation of (A).
Question 17
Assertion (A): Copper is a non-transition element.
Reason (R): Copper has completely filled d-orbitals in its ground state.
Correct Answer: (a) Both (A) and (R) are true and (R) is the correct explanation of (A).
Question 18
Assertion (A): Nucleophilic substitution of iodoethane is easier than chloroethane.
Reason (R): Bond enthalpy of C–I bond is less than that of C–Cl bond.
Correct Answer: (a) Both (A) and (R) are true and (R) is the correct explanation of (A).
Very short answer type Questions
Question 19
The vapour pressure of pure liquid X and pure liquid Y at 25 °C are
120 mm Hg and 160 mm Hg respectively. If equal moles of X and Y are
mixed to form an ideal solution, calculate the vapour pressure of the solution.
(i) Mercury cell delivers a constant potential during its life time.
(ii) In the experimental determination of electrolytic conductance,
Direct Current (DC) is not used.
OR
(b) Define fuel cell with an example. What advantages do the fuel cells
have over primary and secondary batteries?
(a) (i) The concentration of reactants and products remains constant,
therefore the emf remains constant.
(a) (ii) DC causes electrolysis and polarization of electrodes, affecting
accurate conductance measurement.
(OR – b)
A fuel cell is a device that converts chemical energy of a fuel directly
into electrical energy. Example: Hydrogen–oxygen fuel cell.
Advantages:
• High efficiency
• Environment friendly
• Continuous supply of electricity
Question 21
(a) The conversion of molecule A to B followed second order kinetics.
If concentration of A is increased to three times, how will it affect the
rate of formation of B?
(b) Define pseudo first order reaction with an example.
(a) For second order reaction, rate ∝ [A]2
If concentration is tripled, rate increases by 32 = 9 times.
(b) A reaction which is actually of higher order but appears to be
first order due to excess concentration of one reactant is called
pseudo first order reaction. Example: Hydrolysis of ethyl acetate in excess water.
Question 22
(a) Write the IUPAC names of the following :
(i) [Co(NH3)5(ONO)]2+
(ii) K2[NiCl4]
OR
(b) (i) What is a chelate complex? Give one example.
(ii) What are heteroleptic complexes? Give one example.
(a) (i) Pentaammine nitrito-O cobalt(III) ion (a) (ii) Potassium tetrachloronickelate(II)
(OR – b) (i) Chelate complex is formed when a bidentate ligand binds
through two donor atoms. Example: [Cu(en)2]2+
(ii) Complexes containing more than one type of ligand are called
heteroleptic complexes. Example: [Co(NH3)4Cl2]+
Question 23
Write the chemical equation involved in the following reactions :
Do the following conversions in not more than two steps :
(a) CH3CN → CH3COCH3
(b) Benzoic acid → Benzene
(a) CH3CN + CH3MgBr → Hydrolysis → Acetone
(b) Benzoic acid → Soda lime → Benzene
Question 25
Write two differences between DNA and RNA.
DNA
RNA
Contains deoxyribose sugar
Contains ribose sugar
Double stranded
Single stranded
Short answer type Questions
Question 26
(a) (i) Write the mechanism of the following reaction :
2CH3CH2OH
—H+, 413 K→
CH3–CH2–O–CH2–CH3 + H2O
(ii) Why ortho-nitrophenol is steam volatile while para-nitrophenol is not ?
OR
(b) What happens when
(i) Anisole is treated with CH3Cl / anhydrous AlCl3 ?
(ii) Phenol is oxidised with Na2Cr2O7 / H+ ?
(iii) (CH3)3C–OH is heated with Cu / 573 K ?
Write chemical equation in support of your answer.
(a) (i) Mechanism:
Ethanol is protonated to form ethyl oxonium ion. One ethanol molecule
acts as nucleophile and attacks the protonated ethanol, followed by
loss of water forming diethyl ether.
(a) (ii)
Ortho-nitrophenol shows intramolecular hydrogen bonding, lowering
its boiling point and making it steam volatile. Para-nitrophenol
shows intermolecular hydrogen bonding, resulting in higher boiling
point.
(OR – b)
(i) Anisole undergoes Friedel–Crafts alkylation giving
o- and p-methylanisole.
(ii) Phenol is oxidised to p-benzoquinone.
(iii) Tertiary alcohol does not undergo dehydrogenation; it
forms alkene by dehydration.
Question 27
Answer any three of the following :
(a) Which isomer of C5H10 gives a single monochloro compound
C5H9Cl in bright sunlight ?
(b) Arrange the following compounds in increasing order of reactivity
towards SN2 reaction :
(c) p-Dichlorobenzene is more symmetrical and packs better in crystal lattice,
hence higher melting point.
(d) A = Grignard reagent (RMgBr)
B = Alkane (RH)
Question 28
A first order reaction is 50% complete in 30 minutes at 300 K and in
10 minutes at 320 K. Calculate activation energy (Ea) for the
reaction.
[R = 8.314 J K−1 mol−1]
For first order reaction, t1/2 = 0.693 / k
k1 / k2 = t2 / t1 = 30 / 10 = 3
log(k2/k1) = log 3 = 0.4771
Ea = 2.303 R log(k2/k1) × (T1T2 / (T2−T1))
Ea = 52.8 kJ mol−1
Question 29
When 19.5 g of F–CH2–COOH (Molar mass = 78 g mol−1)
is dissolved in 500 g of water, the depression in freezing point is
1 °C. Calculate the degree of dissociation.
(a) Draw the geometrical isomers of [Co(en)2Cl2]+.
Which geometrical isomer is not optically active and why ?
(b) Write the hybridisation and magnetic behaviour of [CoF6]3−.
(a) cis- and trans-isomers exist.
Trans-isomer is optically inactive due to plane of symmetry.
(b) Co3+ = d6, F− is weak field ligand.
Hybridisation = sp3d2
Complex is paramagnetic.
Case-based Questions
Question 31
The carbon–oxygen double bond is polarised in aldehydes and ketones due to
higher electronegativity of oxygen relative to carbon. Therefore they undergo
nucleophilic addition reactions with a number of nucleophiles such as HCN,
NaHSO3, alcohols, ammonia derivatives and Grignard reagents.
Aldehydes are easily oxidised by mild oxidising agents as compared to ketones.
The carbonyl group of carboxylic acid does not give reactions of aldehydes and
ketones. Carboxylic acids are considerably more acidic than alcohols and most
of simple phenols.
Answer the following :
(a) Write the name of the product when an aldehyde reacts with excess alcohol
in presence of dry HCl.
(b) Why carboxylic acid is a stronger acid than phenol ?
(c) (i) Arrange the following compounds in increasing order of their reactivity
towards CH3MgBr :
CH3CHO, (CH3)3C–CO–CH3, CH3–CO–CH3
(ii) Write a chemical test to distinguish between propanal and propanone.
OR
(c) Write the main product in the following :
(i) Cyclohexanone-CHO
—[Ag(NH3)2]+→
(ii) Benzaldehyde
—H2NCONHNH2→
(a) Acetal
(b) Carboxylate ion is stabilised by resonance over two oxygen atoms,
whereas phenoxide ion is less stabilised. Hence carboxylic acids are stronger
acids.
(c) (i)
(CH3)3C–CO–CH3 <
CH3–CO–CH3 <
CH3CHO
(c) (ii) Use Tollen’s test.
Propanal gives silver mirror while propanone does not react.
(OR – c)
(i) Aldehyde group is oxidised to carboxylic acid; ketone remains unchanged.
(ii) Benzaldehyde semicarbazone
Question 32
Carbohydrates are optically active polyhydroxy aldehydes and ketones.
They are also called saccharides. All those carbohydrates which reduce
Fehling’s solution and Tollen’s reagent are referred to as reducing sugars.
Glucose, the most important source of energy for mammals, is obtained by
the hydrolysis of starch. Vitamins are accessory food factors required in the
diet. Proteins are the polymers of α-amino acids and perform various structural
and dynamic functions in the organisms. Deficiency of vitamins leads to many
diseases.
Answer the following :
(a) The penta-acetate of glucose does not react with Hydroxylamine.
What does it indicate ?
(b) Why cannot vitamin C be stored in our body ?
(c) Define the following as related to proteins :
(i) Peptide linkage
(ii) Denaturation
OR
(c) Define the following as related to carbohydrates :
(i) Anomers
(ii) Glycosidic linkage
(a) It indicates that the aldehyde group of glucose is not free and is
present in cyclic (hemiacetal) form.
(b) Vitamin C is water soluble and hence excess is excreted through urine.
(c) (i) Peptide linkage is the –CO–NH– bond formed between two amino acids.
(c) (ii) Denaturation is the loss of biological activity of protein due to
change in its native structure.
(OR – c)
(i) Anomers are stereoisomers differing in configuration at anomeric carbon.
(ii) Glycosidic linkage is the bond formed between two monosaccharide units
through an oxygen atom.
Long answer type Questions
Question 33
(a) (I) Account for the following :
(i) E° value for Mn3+/Mn2+ couple is much more positive than that
for Cr3+/Cr2+.
(ii) Sc3+ is colourless whereas Ti3+ is coloured in an aqueous
solution.
(iii) Actinoids show wide range of oxidation states.
(II) Write the chemical equations for the preparation of KMnO4 from MnO2.
OR
(b) (I) Account for the following :
(i) Transition metals form alloys.
(ii) Ce4+ is a strong oxidising agent.
(II) Write one similarity and one difference between chemistry of Lanthanoids
and Actinoids.
(III) Complete the following ionic equation :
Cr2O72− + 2OH− → ?
(a) (I) (i)
Mn3+ readily gets reduced to Mn2+ which has a stable half-filled
d5 configuration. Hence Mn3+/Mn2+ has high positive E° value,
unlike Cr3+/Cr2+.
(ii)
Sc3+ has d0 configuration, so no d–d transition occurs and it is colourless.
Ti3+ has d1 configuration, allowing d–d transition, hence coloured.
(iii)
Actinoids show variable oxidation states because 5f, 6d and 7s orbitals are
of comparable energy.
(II)
2MnO2 + 4KOH + O2 → 2K2MnO4 + 2H2O
3K2MnO4 → 2KMnO4 + MnO2 + 2KOH
(OR – b)
(I) (i)
Transition metals have similar atomic sizes and can replace each other in
metallic lattices forming alloys.
(ii)
Ce4+ readily gets reduced to Ce3+ attaining stable noble gas
configuration, hence acts as strong oxidising agent.
(II)
Similarity: Both show contraction in atomic radii.
Difference: Actinoids show greater number of oxidation states than lanthanoids.
(III)
Cr2O72− + 2OH− → 2CrO42− + H2O
Question 34
(a) (I) Give reasons :
(i) Aniline on nitration gives good amount of m-nitroaniline, though –NH2
group is o/p directing.
(ii) (CH3)2NH is more basic than (CH3)3N in aqueous solution.
(iii) Ammonolysis of alkyl halides is not a good method to prepare pure
primary amines.
(II) Write the reaction involved in the following :
(i) Carbylamine test
(ii) Gabriel phthalimide synthesis
OR
(b) (I) Write the structures of A, B and C in the following reactions :
(i) C6H5N2+Cl− —CuCN→ A —H2O/H+→ B —NH3, Δ→ C
(ii) Nitrobenzene —Fe/HCl→ A —NaNO2/HCl (273 K)→ B —C2H5OH→ C
(II) Why aniline does not undergo Friedel-Crafts reaction ?
(III) Arrange the following in increasing order of boiling point :
C2H5OH, C2H5NH2, (C2H5)3N
(a) (I) (i)
In acidic medium aniline forms anilinium ion which is meta directing.
(ii)
(CH3)2NH is better solvated than (CH3)3N in water,
making it more basic.
(iii)
Further alkylation leads to mixture of amines.
(II)
(i) RNH2 + CHCl3 + KOH → RNC (foul smell)
(ii) Gabriel synthesis gives primary amines only.
(OR – b)
(I) (i)
A = C6H5CN
B = C6H5COOH
C = C6H5CONH2
(ii)
A = Aniline
B = Benzene diazonium chloride
C = Benzene
(II)
Aniline forms salt with AlCl3, reducing ring activation.
(III)
(C2H5)3N < C2H5NH2 < C2H5OH
Question 35
(a) Conductivity of 2 × 10−3 M methanoic acid is
8 × 10−5 S cm−1. Calculate its molar conductivity and degree
of dissociation if Λ°m for methanoic acid is
404 S cm2 mol−1.
(b) Calculate ΔrG° and log Kc for the given reaction at 298 K :
Ni(s) + 2Ag+(aq) ⇌ Ni2+(aq) + 2Ag(s)
E°Ni2+/Ni = −0.25 V,
E°Ag+/Ag = +0.80 V
1 F = 96500 C mol−1
(i) Protect –NH2 group by acetylation, then bromination, followed by hydrolysis.
(ii) Convert ethanoic acid to acetamide, then Hoffmann bromamide reaction.
(iii) Reduce nitrile using LiAlH4.
Question 28
0.3 g of acetic acid dissolved in 30 g benzene shows depression in freezing point of 0.45°C.
Calculate percentage association of acid if it forms dimer.
Moles of acetic acid = 0.3 / 60 = 0.005
Molality = 0.005 / 0.03 = 0.1667
ΔTf = iKfm
0.45 = i × 5.12 × 0.1667
i = 0.527
For dimerisation: i = 1 − α/2
α = 0.946 ≈ 94.6%
Question 29
The rate of reaction doubles when temperature changes from 27°C to 37°C.
Calculate activation energy.
Using Arrhenius equation:
log(k2/k1) = Ea / 2.303R × (T2 − T1) / (T1T2)
Ea = 52.9 kJ mol−1
Question 30
Write the structure of product when D-glucose reacts with (any three):
The polarity of C – X bond of alkyl halides is responsible for their nucleophilic substitution, elimination and their reaction with metal atoms to form organometallic compounds. Alkyl halides are prepared by the free radical halogenation of alkanes, addition of halogen acids to alkenes, replacement of –OH group of alcohols with halogens using phosphorus halides, thionyl chloride or halogen acids. Aryl halides are prepared by electrophilic substitution of arenes. Nucleophilic substitution reactions are categorised into SN1 and SN2 on the basis of their kinetic properties. Chirality has a profound role in understanding the SN1 and SN2 mechanism.
Answer the following questions :
(i) What happens when bromobenzene is treated with Mg in the presence of dry ether ?
(ii) Which compound in each of the following pairs will react faster in SN1 reaction with OH− ?
(1) CH2=CH–CH2–Cl or CH3–CH2–CH2–Cl
(2) (CH3)3C–Cl or CH3Cl
(iii) Write the equations for the preparation of 1-iodobutane from :
(1) 1-chlorobutane
(2) but-1-ene
OR
(iii) Write the structure of the major products in each of the following reactions :
(1) CH3–CH(Br)–CH3 + KOH (ethanol), heat
(2) Chlorobenzene + CH3COCl / anhyd. AlCl3
(i) Bromobenzene reacts with magnesium in dry ether to form phenyl magnesium bromide (Grignard reagent).
C6H5Br + Mg → C6H5MgBr
(ii)
(1) CH2=CH–CH2–Cl (allyl chloride) reacts faster due to resonance-stabilised carbocation.
(2) (CH3)3C–Cl reacts faster due to formation of stable tertiary carbocation.
(iii)
(1) CH3CH2CH2CH2Cl + NaI (acetone) → CH3CH2CH2CH2I + NaCl
(2) CH2=CH–CH2CH3 + HI (peroxide absent) → CH3CH2CH2CH2I
Coordination compounds are widely present in the minerals, plant and animal worlds and are known to play many important functions in the area of analytical chemistry, metallurgy, biological systems and medicine. Alfred Werner’s theory postulated the use of two types of linkages (primary and secondary), by a metal atom/ion in a coordination compound. He predicted the geometrical shapes of a large number of coordination entities using the property of isomerism. The Valence Bond Theory (VBT) explains the formation, magnetic behaviour and geometrical shapes of coordination compounds. It, however, fails to describe the optical properties of these compounds. The Crystal Field Theory (CFT) explains the effect of different crystal fields (provided by the ligands taken as point charges) on the degeneracy of d-orbital energies of the central metal atom/ion.
Answer the following questions :
(i) When a coordination compound NiCl2·6H2O is mixed with AgNO3 solution, 2 moles of AgCl are precipitated per mole of the compound. Write the structural formula of the complex and secondary valency for Ni2+.
(ii) Write the IUPAC name of the ionisation isomer of [Co(NH3)5(SO4)]Cl.
(iii) Using Valence Bond Theory, predict the geometry and magnetic nature of :
(1) [Ni(CO)4]
(2) [Fe(CN)6]3−
OR
(iii) Give reasons :
(1) Low spin tetrahedral complexes are not formed.
(2) [Co(NH3)6]3+ is an inner orbital complex whereas [Ni(NH3)6]2+ is an outer orbital complex.
(1) Δt is always small in tetrahedral complexes, hence pairing does not occur.
(2) Co3+ causes pairing of electrons while Ni2+ does not.
Long answer type Questions
Question 33
(a) (i) Account for the following :
(1) Transition metals form complex compounds.
(2) The E°Mn2+/Mn value for manganese is highly negative whereas
E°Mn3+/Mn2+ is highly positive.
(3) Cu+ ion is unstable in aqueous solution.
(ii) Write the equations involved in the preparation of KMnO4
from Pyrolusite ore (MnO2).
OR
(b) (i) Identify the following :
(1) Transition metal of 3d series that exhibits only one oxidation state.
(2) Transition metal of 3d series that acts as a strong reducing agent in +2 oxidation
state in aqueous solution.
(ii) Complete and balance the following equations :
(1) Cr2O72− + 14H+ + 6Fe2+ → ____
(2) KMnO4heat → ____
(iii) What is Misch metal ? Write its one use.
(a) (i) (1)
Transition metals have vacant d-orbitals and high charge density, enabling them to
form coordinate bonds with ligands and hence complex compounds.
(2)
Mn2+ has a stable half-filled 3d5 configuration, therefore Mn → Mn2+ is difficult
and E° value is highly negative. Mn3+ readily gets reduced to Mn2+, so
E°Mn3+/Mn2+ is highly positive.
(3)
Cu+ undergoes disproportionation in aqueous solution to form Cu2+ and Cu,
hence it is unstable.
(iii)
Misch metal is an alloy of rare earth metals. It is used in lighter flints.
Question 34
(a) (i) An organic compound (X) having molecular formula C5H10O can
show various properties depending on its structures. Draw each of the structures if it
(1) gives positive iodoform test.
(2) shows Cannizzaro’s reaction.
(3) reduces Tollen’s reagent and has a chiral carbon.
(ii) Write the reaction involved in the following :
(1) Wolff-Kishner reduction
(2) Hell-Volhard-Zelinsky reaction
OR
(b) (i) How can you convert each of the following compounds to Benzoic acid ?
(1) Acetophenone
(2) Ethylbenzene
(3) Bromobenzene
(ii) Arrange the following compounds in increasing order of :
(1) Acidic character : O2N-CH2-COOH, F-CH2-COOH, CN-CH2COOH
(b) State Kohlrausch law of independent migration of ions.
Why does the conductivity of a solution decrease with dilution ?
(a)
E°cell = 0.76 V
E = 0.76 − (0.059/2) log(10)
E = 0.73 V
(b)
Kohlrausch law states that at infinite dilution, molar conductivity is the sum
of individual ionic conductivities. Conductivity decreases with dilution due
to decrease in number of ions per unit volume.
