AMIT ARORA WORLD OF CHEMISTRY: November 2016

50 Short Sure Questions Chemistry class-XII March 2015-16

Q1	(i) Why is Frenkel defect not found in pure alkali metal halides. (ii) What happens to the structure of CsCl when it is heated to about 760 k? (iii) Fe₃O₄ is ferrimagnetic at room temperature and becomes paramagnetic at 850 K.Why? (iv) When atoms are placed at the corners of all 12 edges, how many atoms are present per unit cell? Ans→Because ions can not get into interstitial sites due to their larger size.(b) CsCl structure transforms into NaCl structure.(c) due to randomization of spins at high temp.(d) at corners 8 x 1/8 = 1 atom
Q2	Explain intrinsic and extrinsic semiconductors with suitable examples. Ans→ Extrinsic contains impurities(B doped with Si) & intrinsic no impurities ( Si and Ge)
Q3	A metal crystallises into two cubic phases FCC & BCC whose edge lengths are 3.5 & 3.0 A⁰ respectively. Calculate the ratio of densities of FCC & BCC. Ans→ d(fcc) = 4 x M / N_A x (3.5)³, d(bcc) = 2 x M / N_A(3)³ d(fcc) / d(bcc) = 4 x 3³ / 2 x (3.5)³ = 1.26 ans
Q4	(a)Why is elevation in boiling point of water different in the following cases; (i) 0.1 M NaCl solution (ii) 0.1 M sugar solution (b)Which is more concentrated 1 M or 1 m solution & why? (c)Two liquids A & B boil at 145⁰C 190⁰C respectively. Which of them will have higher V.P at 80⁰C? Ans→(a) 0.1M NaCl due to more number of ions (b) 1Molar because it contains solvent & solute both(c) liq A
Q5	State Henry^,S law for solubility of a gas in liquid.Explain the significance of Henry^,S constant(K_H). At the same temperature, H₂ is more soluble than He in water. Which of them will have higher value of K_H& Why? Ans→ statement, Solubility α 1 / K_H, H₂ has lower value of K_H
Q6	Molar mass of CH₃CH₂CHClCOOH = 122.5, moles of CH₃CH₂CHClCOOH= 10/122.5 = 0.0816, m = 0.0816/ 0.250 kg = 0.3264 α = √ K_a/C = √ 1.4 x 10^—³/ 0.3264 = 0.065, i—1 i—1 i—1 α = --------, 0.065 = -------- = -------, i = 1.065 m—1 2—1 1 ∆T_f = i x K_f x m = 1.065 x 1.86 x 0.3264 = 0.65⁰ (ANS)
Q7	Which will have greater molar conductivity? (i) Solution containing 1 mol of KCl in 200 ml or 1 mol of KCl in 500 ml. (ii) Solution containing 1 mol of LiCl in 500 ml or 1 mol of KCl in 500 ml. (b) Why is it not possible to determine Λ^∞_m for weak electrolytes by extrapolation? Ans→(a) (i) 1 mol of KCl in 500 ml . (ii) 1 mol of KCl in 500 ml (b) graph does not intersect the conc axis.
Q8	(a) Can a solution of 1 M CuSO₄ be stored in a Ni vessel? E⁰(Cu⁺²/Cu) = 0.34 V, E⁰ (Ni⁺²/Ni) = -0.25V. (b) Suggest a way to determine the Λ^∞_m value of water. (c) Which reaction is feasible (i) I₂ + 2e^-→ 2I^-, E⁰ = 0.54 V. (ii) Br₂ + 2e^- → 2Br^-, E⁰ = 1.08 V. Ans→ (a) No. because Cu reduces due to its high reduction potential. (b) Λ^∞_m(H₂O) → Λ^∞_m(HCl) + Λ^∞_m(NaOH) -Λ^∞_m(NaCl) (c) reaction (ii) is feasible because E⁰ of Br₂ is more than I₂.
Q9	A solution of Ni(NO₃)₂is electrolyzed between Pt electrodes using a current of 5 A for 20 minutes. What mass of Ni is deposited at the cathode? Ans→ Q = I x t = 5 x 20 x 60 = 6000 coulomb. Ni⁺² + 2e^- = Ni ( atomic mass of Ni = 58.7) 2 x 96500 coulomb candeposite = 58.7gm Ni 6000 coulomb candeposite = 58.7 x 6000/2 x 96500 = 1.28gm(Ans)
Q10	The reaction A + B → C has zero order. What is the rate equation? Ans→ rate = k(A)⁰(B)⁰
Q11	Define activation energy of a reaction. Ans→ Extra amount of energy that is supplied from outside so that colliding particles must produce Effective Collisions.
Q12	Give an example of a pseudo first order reaction. Ans→CH₃COOC₂H₅ + H₂O → CH₃COOH + C₂H₅OH
Q13	How does the value of rate constant vary with reactant concentration ? Ans→α 1/ C^n-1
Q14	Identify the order of reaction. Ans→Zero order
Q15	Define the following terms: (i) Zeta potential (ii) Kraft temperature (iii) Emulsion Ans→(i) potential difference between the fixed layer and the diffused layer of opposite charges is called the electrokinetic potential or zeta potential. (ii)The formation of micelles takes place only above a particular temperature called Kraft temperature (Tk) and above a particular concentration called critical micelle concentration (CMC). (iii) These are liquid-liquid colloidal systems, i.e., the dispersion of finely divided droplets in another liquid. If a mixture of two immiscible or partially miscible liquids is shaken, a coarse dispersion of one liquid in the other is obtained which is called emulsion.
Q16	What is Hardy Schulze rule? What modification do you suggest in this law? Ans→ The power of coagulation is directly proportional to the fourth power of active ion. Law must be modified as; When equimolar proportions of two oppositely charged sols are mixed, they mutually neutralize their charge and both get coagulated
Q17	Discuss the effect of temperature and pressure on adsorption of gases by solids Ans→Book
Q18	Explain what is observed when? (i) An electrolyte is added to ferric hydroxide sol. (ii) An emulsion is subjected to centrifugation. (iii) Direct current is passed through a colloidal solution. Ans→(a) Coagulation (b) de-emulsification (c) electrophoresis.
Q19	What is pyrometallurgy? Ans→ The process of extraction of metal by heating the metal oxide with a suitable reducing agent is called thermal reduction or pyrometallurgy
Q20	What is the role of cryolite in electrometallurgy of Aluminium? Ans→ To reduce the melting point of alumina.
Q21	Out of C and CO, Which is better reducing agent at 673K&Why? Ans→ When C reacts with O₂ two reactions are possible; C + O₂ → CO₂(1) 2C+O₂→2CO (2). It is clear from Ellingham diagram that at 673K, ∆G⁰ for the oxidation of CO is more –ive than the reaction 1 & 2. Therefore CO is better reducing agent.
Q22	Metals do not occur in nature as nitrates. Why? Ans→ Nitrates of almost all metals are soluble in water.
Q23	How is nitric acid manufactured by Ostwald process? Give all chemical reactions involved in the process. Ans→Catalytic oxidation of NH₃ by atmospheric oxygen Nitric oxide thus formed combines with O₂ to give NO₂ NO₂ so formed, dissolved in water to give Nitric acid
Q24	Give reason for the followings: • Nitrogen does not form pentahalides. • All five bonds in PCl₅ are not equivalent. • SF₆can not be hydrolysed easily. Ans→(A) Absence of vacant d orbital (b) Axial bond pairs suffer more repulsion than equatorial bond pairs. (c) Sulphur is sterically protected.
Q25	Arrange the following as indicated: 3 (a) HF ,HCl , HBr , HI ( decreasing order of acidic character) (b) NH₃, PH₃, AsH₃, SbH₃( decreasing order of themal stability) (c) H₂O, H₂S, H₂Se, H₂Te ( decreasing order of reducing property) Ans→(a) HF <HCl<HBr< HI (b) (b) NH₃> PH₃> AsH₃> SbH₃(c) H₂O< H₂S< H₂Se< H₂Te
Q26	What is lanthaniodcontraction? What is its reason? What are its consequences? Ans→ BooK
Q27	Account for the following; (a) The enthalpies of atomisation of the transition metals are very high. (b) Transition metals generally form coloured ions. (c) Transition metals and many of their compounds show paramagnetic behaviour. Ans→(a) due to unpaired electrons (b) due to d – d transition (c) due to unpaired electrons
Q28	Describe the preparation of K₂Cr₂O₇ from chromite ore. What is the effect of increasing p^H on a solution of potassium dichromate? Ans→4FeCr₂O₄ + 8Na₂CO₃(or NaOH) + 7O₂ → 8Na₂CrO₄ + 2Fe₂O₃ +8CO₂(or 8H₂O) 2Na₂CrO₄+ H₂SO₄ → Na₂Cr₂O₇ + Na₂SO₄ + H₂O Na₂Cr₂O₇ + KCl → K₂Cr₂O₇ + 2 NaCl On increasing the P^H dichromate ion (orange) will change into chromate ion (yellow). K₂Cr₂O₇ + KOH → K₂CrO₄ + H₂O
Q29	What is meant by chelate effect? Give an example. Ans→ The complexes formed by chelating ligands like (en) and EDTA are more stable than formed by monodentate ligands like H₂O and NH₃. This enhanced stability of complexes containing ligands is called chelate effect. Example [PtCl₂(en)]
Q30	Define the following terms; (a) Homoleptic complexes (b) Coordination entity (c) ligands Ans→(a)The complex in which metal ion is bonded to only one kind of donor ligands. eg [Co(NH₃)]⁺³ (b) The central metal ion together with ligands directly attached to it is termed as coordination sphere. It is written in square bracket. example [Co(NH₃)]⁺³
Q31	(a) Geometrical isomerism is not possible in tetrahedral complexes. Why? (b) Give the evidence that [Co (NH₃)₅Cl]SO₄ and [Co(NH₃)₅ SO₄]Cl are ionisational isomers. Ans→(a) All positions are cis,There is no trans position. (b) They give different types of ions SO₄^-2 and Cl^- ions respectively.
Q32	Write IUPAC names of (a) CH₃-NH-CH(CH₃)₂ (b) m-BrC₆H₄NH₂ . Ans→(a) N-methyl propan-2-amine (b) 3-bromo benzenamine
Q33	Explain Why (a)Alkyl halides, though polar,are immiscible with water. (b) Grignard reagents should be prepared under anhydrous conditions (c) o-nitrophenol is more steam volatile than p-nitrophenol. (d) o-methoxyphenol is less acidic than o-nitrophenol. Ans→(a) Alkyl halides are polar compounds and they do not form H-bonding with water. (b) They react with water. R-Mg-X + HOH → R-H + Mg(OH) X (c) o-nitro phenol is steam volatile due to intramolecular H- bonding and intermolecular H- bonding in p-nitro phenol. (d) o-methoxy phenol is less acidic because of +I effect in it.
Q34	Write the equations for the following reactions. (a) Riemer-Tiemann reaction (b) Finkelstein reaction Ans→Reimer-Tiemann reaction; Phenol + CHCl₃+ NaOH + Heat → Salicylaldehyde. Phenol + CCl₄ + NaOH + Heat → Salicylic acid. Finkelstein reaction ; CH₃CH₂Br +NaI → CH₃CH₂I + NaBr OR CH₃CH₂Cl +NaI → CH₃CH₂I + NaCl
Q35	Arrange the following in increasing order of basic strength . (a) Pri, Sec , Ter amine. (gas phase) . (b) Ans→(a) Pri< Sec < Ter amine. (b) Sec >Pri> Ter.
Q36	Account for the following (a) There are two –NH₂ groups in semicarbazides.However, only one is involved in the formation of semicabazones. (b) FCH₂COOH is stronger than ClCH₂COOH. Ans→(a) methylamine gives carbylamine test. (b) benzylamine reacts with HNO₂ to form C₆H₅CH₂N₂Cl which is unstable and form C₆H₅CH₂OH with water.
Q37	An organic compound A (C₂H₆O) reacts with sodium to form compound B with evolution of hydrogen and gives a yellow compound C when treated with iodine &NaOH. On heating with conc H₂SO₄ at 413 K, it gives a compound D(C₄H₁₀O) which on treatment with HI at 373K gives E. D is also obtained when B is heated with E.Identify the compounds and write the equations involved. Ans→
Q38	Name the reagents used in the following reactions. (a) Oxidation of a primary alcohol to aldehyde. (b) Bromination of phenol to 2.4.6 tribromophenol. (c) butan-2-one to butan-2-ol. Ans→(a) Pyridinium Chloro Chromate PCC in CH₂Cl₂ (b) Br₂/ H₂O(c) H₂/ Ni, LiAlH₄, NaBH₄
Q39	Account for the following (a) Ortho-nitrophenol is more acidic than ortho-methoxyphenol/. (b) Alcohols are weaker acid than water. (c) Alcohols are more soluble in water than hydrocarbons Ans→(a) Due to +I effect of OCH₃ group, H⁺can not be released easily from ortho-methoxyphenol. (b) Due to +I effect of alkyl group in alcohol, H⁺can not be released easily from ortho-methoxyphenol. (c) alcohols forms H-bonding with water.
Q40	Give equations for the following reactions. (a) Dilute HNO₃ with phenol. (b) Bromine with CS₂ with phenol. (c) 1-phenylethanol from a suitable alkene. Ans→(a) O-nitrophenol and P-nitrophenol (b) O-bromophenol and P-bromophenol (c)
Q41	What are reducing and non-reducing sugars? Give one example of each. Ans→ Sugars which can reduce the Fehling^,S solution or Tollen^,S reagent are called reducing sugars. Examples- all monosachharides, ribose,mannose,andgalactose. Sugars which can not reduce the Fehling^,S solution or Tollen^,S reagent are called non reducing sugars. Examples-maltose,lactose and sucrose.
Q42	What happens when D-glucose is treated with the following reagents? (a) HI (b) Bromine water (c) conc HNO₃ Ans→(a) glucose + HI→ n-hexane (b) glucose + Br₂(aq)→ gluconic acid[ COOH—(CH₂OH)₄—CH₂OH]. (c) glucose + Conc HNO₃ → glucaric or sachharic acid [COOH—(CH₂OH)₄—COOH].
Q43	What are essential and non-essential amino acids? Give one example of each type. Ans→ Essential-Which can not be synthesized in our body.Valine and Leucine Non-essential- Which can be synthesized in our body.Glycine and Alanine.
Q44	Name the polymer used for making nonstick utencils. Name→(I) Teflon, Melamine
Q45	Give one point of difference between thermosets &thermoplasts. Ans→BooK
Q46	--- (--CH₂-CH---)_n--- │ C₆H₅ Is the above polymer homopolymer or copolymer? Is it an addition or condensation? Ans→ Homo & addition.
Q47	What is the difference between polyacrylate& polyester? Ans→ polyacrylate—homo,addition,polymerization across C=C bond. Polyester—copolymer,condensation,polymerization through ester linkage.
Q48	Why do drugs designed to cure some ailment in one organ in the body not affect the other parts? Explain with an example. Ans→ An important point about the receptors is that they are not disturbed evenly around the body. For example- heart has more β adrenergic receptors than α adrenergic receptors .This means that a drug designed to interact with β adrenergic receptors will act on heart rather than a tissue which are rich in α adrenergic receptors .
Q49	Define the following terms with one example(Any two) (a) Antipyretics (b) Antioxidants (c) Antifertility drugs Ans→ Antipyretics—The chemical substances used to bring down the body temperature are called antipyretics.Paracetamol.Phenacetin, Analgin. Antioxidants--The substance which when added to the fat and fat containing foods prevents their oxidation and thus prolongs their life.Withoutthem,fatty foods such as potato chips can not be stored for long time. Examples—Butylatedhydroxyanisol(BHA), Butylatedhydroxy toluene (BHT), Propyl gallate(PG),Tertiary butyl hydroquinone(TBHQ), Antifertility drugs—The chemicals which are used to control pregnancy are called antifertility drugs.They are mostly hormonal contraceptives and are available for females only.They are gonadal steroids(Oestrgen and Progesteron).
Q50	Account for the followings: (a) The use of aspartame is limited to cold foods and drinks. (b) Synthetic detergents are called soapless soaps. (c) Medicines should not be taken without consulting doctors. Ans→(a) It decomposes on heating. It nearly 100 times as sweet as cane sugar.Chemically it is methyl ester of dipeptide of Aspartic acid and phenylalanine. (b) Synthetic detergents are sodium compounds of benzene sulphonic acids whereas soaps are sodium compounds of higher fatty acids.Soaps are based on oils. Synthetic detergents are based on hydrocarbons. (c) Medicines should not be taken without consulting doctors because their wrong choice and over dose can cause havoc and may even prove to be fatal.

50 Short Sure Questions Chemistry class-XII March 2016-17

Q1	Calculate the packing efficiency of a metal crystal for a simple cubic lattice. Suppose edge length of unit cell = a Radius of sphere = r Sphere are touching each-other a = 2r No of spheres per unit cell = 1 Volume of sphere = 4πr³/3 Volume of unit cell = a³ = (2r)³ = 8r³ Packing efficiency 4πr³/3 = ---------- x 100 = 52.4 % 8r³
Q2	An element with density 2.8 gm/ cm^-3 forms a fcc unit cell with edge length 4 x 10^-8 cm. calculate the molar mass of element. ( N_A = 6.022 x 10²³ mol^-1) Ans→
Q3	How will tou distinguish between the following pairs? (a) Tetrahedral and octahedral voids (b) crystal lattice and unit cell Ans→ (a) Tetrahedral void→ Vacant space among four spheres having tetrahedral arrangement is called tetrahedral void. Octahedral void →The void formed by two equilateral triangles (six spheres) with apices in opposite directions is called octahedral void. (b) A regular three dimensional arrangement of points in space is called a crystal lattice. The smallest repeating unit in a space lattice in three dimensional form is called a unit cell.
Q4	State Raoult^,s law for solutions of volatile liquid components. Taking a suitable example , explain the meaning of positive deviation from Raoult^,s law. Ans→ This law states that at a given temperature ,the partial vapour pressure of each component in the solution is equal to the product of vapour pressure of pure component and its mole fraction. Consider two liquids A and B. positive deviation from Raoults law→ Consider a binary solution of two components A and B. These solutions are formed when A—B interactions are weaker than A—A and B—B interactions. The escaping tendency of molecules increases. For these solutions P_A>P_A⁰X_A and P_B> P_B⁰X_B example ethanol and water. Ethanol and acetone
Q5	Explain the following; (a) Hanry^,s law about the dissolution of a gas in a liquid. (b) Boiling point elevation constant for a solvent. Answer → definition in book
Q6	What type of deviation is shown by a mixture of ethanol and acetone? Give reason. Ans→It shows positive deviation It is due to the weaker interaction between acetone and ethanol than ethanol-ethanol interaction.
Q7	(i) Write colligative property which is used to find molecular mass of macromolecules. (ii) In non-ideal solution, what type of deviation shows the formation of minimum boiling azeotropes? Ans→ (i) Osmotic pressure (ii) Positive deviation from Raoult,s law
Q8	What type of cell is a lead storage battery? Write the anode and cathode reactions and the over all cell reactions. And the overall cell reactions occurring in the use of a lead storage battery. Ans→ Lead storage battery is a secondary cell.It can be recharged by passing electric current again & again.In these cells reactions are reversible. Anode→ Pb + SO₄^-2 → PbSO₄ + 2e^- Cathode→ PbO₂ + 4H⁺ + SO₄^-2 + 2e^- → 2PbSO₄ + 2H₂O Overall→ Pb + PbO₂ +2H₂SO₄→ 2PbSO₄ + 2H₂O
Q9	A solution of Ni(NO₃)₂is electrolyzed between Pt electrodes using a current of 5 A for 20 minutes. What mass of Ni is deposited at the cathode? Ans→ Q = I x t = 5 x 20 x 60 = 6000 coulomb. Ni⁺² + 2e^- = Ni ( atomic mass of Ni = 58.7) 2 x 96500 coulomb candeposite = 58.7gm Ni 6000 coulomb candeposite = 58.7 x 6000/2 x 96500 = 1.28gm(Ans)
Q10	State Kohlrausch law of independent migration of ions. Why does the conductivity of a solution decrease with dilution. Ans→ The law states that limiting molar conductivity of an electrolyte can be stated as the sum of individual contributions of the anions and cations of the electrolyte. Conductivity of solution decreases as the number of ions per unit volume of the solution decreases.
Q11	Define activation energy of a reaction. Ans→ Extra amount of energy that is supplied from outside so that colliding particles must produce Effective Collisions.
Q12	Give an example of a pseudo first order reaction. Ans→CH₃COOC₂H₅ + H₂O → CH₃COOH + C₂H₅OH
Q13	How does the value of rate constant vary with reactant concentration ? Ans→α 1/ C^n-1
Q14	.Write units of rate constants for zero order and second order reactions if the concentration is expressed in mol L^- and time in second. Ans→ Zero order reaction ----- mol L^-1S^-1. Second order reaction ---mol^-1 L S^-1.
Q15	Express the rate of the following reaction in terms of disappearance of hydrogen in the reaction, N₂ + 3H₂ → 2NH₃
Q16	.Rate constant of a first order reaction is 60 S^-1. How much time will it take to reduce the concentration of the reactant to 1/10^th of its initial value?
Q17	Define adsorption with an example. Why is adsorption exothermic in nature? Write the type of adsorption based nature of forces between adsorbate and adsorbent. Answer→ The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is termed adsorption. eg gases taken in a closed vessel containing powdered charcoal. Due to bond formation / heat released/ interaction between adsorbate and adsorbent. Physical ( Van der waal adsorption) and chemical ( Langmuir adsorption).
Q18	Explain what is observed when? (i) An electrolyte is added to ferric hydroxide sol. (ii) An emulsion is subjected to centrifugation. (iii) Direct current is passed through a colloidal solution. Ans→(a) Coagulation (b) de-emulsification (c) electrophoresis.
Q19	What is pyrometallurgy? Ans→ The process of extraction of metal by heating the metal oxide with a suitable reducing agent is called thermal reduction or pyrometallurgy
Q20	What is the role of cryolite in electrometallurgy of Aluminium? Ans→ To reduce the melting point of alumina.
Q21	Out of C and CO, Which is better reducing agent at 673K&Why? Ans→ When C reacts with O₂ two reactions are possible; C + O₂ → CO₂(1) 2C+O₂→2CO (2). It is clear from Ellingham diagram that at 673K, ∆G⁰ for the oxidation of CO is more –ive than the reaction 1 & 2. Therefore CO is better reducing agent.
Q22	Metals do not occur in nature as nitrates. Why? Ans→ Nitrates of almost all metals are soluble in water.
Q23	How is nitric acid manufactured by Ostwald process? Give all chemical reactions involved in the process. Ans→Catalytic oxidation of NH₃ by atmospheric oxygen Nitric oxide thus formed combines with O₂ to give NO₂ NO₂ so formed, dissolved in water to give Nitric acid
Q24	Give reason for the followings: • Nitrogen does not form pentahalides. • All five bonds in PCl₅ are not equivalent. • SF₆can not be hydrolysed easily. Ans→(A) Absence of vacant d orbital (b) Axial bond pairs suffer more repulsion than equatorial bond pairs. (c) Sulphur is sterically protected.
Q25	Arrange the following as indicated: 3 (a) HF ,HCl , HBr , HI ( decreasing order of acidic character) (b) NH₃, PH₃, AsH₃, SbH₃( decreasing order of themal stability) (c) H₂O, H₂S, H₂Se, H₂Te ( decreasing order of reducing property) Ans→(a) HF <HCl<HBr< HI (b) (b) NH₃> PH₃> AsH₃> SbH₃(c) H₂O< H₂S< H₂Se< H₂Te
Q26	What is lanthaniodcontraction? What is its reason? What are its consequences? Ans→ BooK
Q27	Account for the following; (a) The enthalpies of atomisation of the transition metals are very high. (b) Transition metals generally form coloured ions. (c) Transition metals and many of their compounds show paramagnetic behaviour. Ans→(a) due to unpaired electrons (b) due to d – d transition (c) due to unpaired electrons
Q28	Describe the preparation of K₂Cr₂O₇ from chromite ore. What is the effect of increasing p^H on a solution of potassium dichromate? Ans→4FeCr₂O₄ + 8Na₂CO₃(or NaOH) + 7O₂ → 8Na₂CrO₄ + 2Fe₂O₃ +8CO₂(or 8H₂O) 2Na₂CrO₄+ H₂SO₄ → Na₂Cr₂O₇ + Na₂SO₄ + H₂O Na₂Cr₂O₇ + KCl → K₂Cr₂O₇ + 2 NaCl On increasing the P^H dichromate ion (orange) will change into chromate ion (yellow). K₂Cr₂O₇ + KOH → K₂CrO₄ + H₂O
Q29	What is meant by chelate effect? Give an example. Ans→ The complexes formed by chelating ligands like (en) and EDTA are more stable than formed by monodentate ligands like H₂O and NH₃. This enhanced stability of complexes containing ligands is called chelate effect. Example [PtCl₂(en)]
Q30	Define the following terms; (a) Homoleptic complexes (b) Coordination entity (c) ligands Ans→(a)The complex in which metal ion is bonded to only one kind of donor ligands. eg [Co(NH₃)]⁺³ (b) The central metal ion together with ligands directly attached to it is termed as coordination sphere. It is written in square bracket. example [Co(NH₃)]⁺³
Q31	(a) Geometrical isomerism is not possible in tetrahedral complexes. Why? (b) Give the evidence that [Co (NH₃)₅Cl]SO₄ and [Co(NH₃)₅ SO₄]Cl are ionisational isomers. Ans→(a) All positions are cis,There is no trans position. (b) They give different types of ions SO₄^-2 and Cl^- ions respectively.
Q32	Write IUPAC names of (a) CH₃-NH-CH(CH₃)₂ (b) m-BrC₆H₄NH₂ . Ans→(a) N-methyl propan-2-amine (b) 3-bromo benzenamine
Q33	Explain Why (a)Alkyl halides, though polar,are immiscible with water. (b) Grignard reagents should be prepared under anhydrous conditions (c) o-nitrophenol is more steam volatile than p-nitrophenol. (d) o-methoxyphenol is less acidic than o-nitrophenol. Ans→(a) Alkyl halides are polar compounds and they do not form H-bonding with water. (b) They react with water. R-Mg-X + HOH → R-H + Mg(OH) X (c) o-nitro phenol is steam volatile due to intramolecular H- bonding and intermolecular H- bonding in p-nitro phenol. (d) o-methoxy phenol is less acidic because of +I effect in it.
Q34	Write the equations for the following reactions. (a) Riemer-Tiemann reaction (b) Finkelstein reaction Ans→Reimer-Tiemann reaction; Phenol + CHCl₃+ NaOH + Heat → Salicylaldehyde. Phenol + CCl₄ + NaOH + Heat → Salicylic acid. Finkelstein reaction ; CH₃CH₂Br +NaI → CH₃CH₂I + NaBr OR CH₃CH₂Cl +NaI → CH₃CH₂I + NaCl
Q35	Arrange the following in increasing order of basic strength . (a) Pri, Sec , Ter amine. (gas phase) . (b) Ans→(a) Pri< Sec < Ter amine. (b) Sec >Pri> Ter.
Q36	Account for the following (a) There are two –NH₂ groups in semicarbazides.However, only one is involved in the formation of semicabazones. (b) FCH₂COOH is stronger than ClCH₂COOH. Ans→(a) methylamine gives carbylamine test. (b) benzylamine reacts with HNO₂ to form C₆H₅CH₂N₂Cl which is unstable and form C₆H₅CH₂OH with water.
Q37	Complete each synthesis by giving missing reagents or products in the following. Ans→
Q38	Name the reagents used in the following reactions. (a) Oxidation of a primary alcohol to aldehyde. (b) Bromination of phenol to 2.4.6 tribromophenol. (c) butan-2-one to butan-2-ol. Ans→(a) Pyridinium Chloro Chromate PCC in CH₂Cl₂ (b) Br₂/ H₂O(c) H₂/ Ni, LiAlH₄, NaBH₄
Q39	Account for the following (a) Ortho-nitrophenol is more acidic than ortho-methoxyphenol/. (b) Alcohols are weaker acid than water. (c) Alcohols are more soluble in water than hydrocarbons Ans→(a) Due to +I effect of OCH₃ group, H⁺can not be released easily from ortho-methoxyphenol. (b) Due to +I effect of alkyl group in alcohol, H⁺can not be released easily from ortho-methoxyphenol. (c) alcohols forms H-bonding with water.
Q40	An organic compound with molecular formula C₉H₁₀O forms 2.4 DNP derivative, reduces Tollens reagent and undergoes Cannizzaro reaction. On vigorous oxidation , it gives 1.2 benzenedicarboxylic acid. Identify the compound. NCERT Q,No 12.10 page 378 Answer→
Q41	What are reducing and non-reducing sugars? Give one example of each. Ans→ Sugars which can reduce the Fehling^,S solution or Tollen^,S reagent are called reducing sugars. Examples- all monosachharides, ribose,mannose,andgalactose. Sugars which can not reduce the Fehling^,S solution or Tollen^,S reagent are called non reducing sugars. Examples-maltose,lactose and sucrose.
Q42	What happens when D-glucose is treated with the following reagents? (a) HI (b) Bromine water (c) conc HNO₃ Ans→(a) glucose + HI→ n-hexane (b) glucose + Br₂(aq)→ gluconic acid[ COOH—(CH₂OH)₄—CH₂OH]. (c) glucose + Conc HNO₃ → glucaric or sachharic acid [COOH—(CH₂OH)₄—COOH].
Q43	What are essential and non-essential amino acids? Give one example of each type. Ans→ Essential-Which can not be synthesized in our body.Valine and Leucine Non-essential- Which can be synthesized in our body.Glycine and Alanine.
Q44	Explain the term co-polymerisation and give two examples of co-polymers and reactions for their preparation. Answer→
Q45	Write the name of the monomers used for getting the following polymers. (i) Terylene (ii) Nylon-6,6 Answer → (i) Ethylene glycol and terephthalic acid ( ethane 1.2 diol and benzene 1.2 dicarboxylic acid) (ii) Hexamethylene diamine and adipic acid
Q46	Write two uses of each of the following polymers: (i) Polyproplene (ii) PVC (iii) Nylon-6,6 Answer→ Uses : (i) Polypropene → Ropes , toys , pipes and fibres (ii) PVC → Rain coat, insulating material, and water pipes (iii) Nylon6,6 → sheets, bristles, brushes and textile industry
Q47	What is the difference between polyacrylate& polyester? Ans→ polyacrylate—homo,addition,polymerization across C=C bond. Polyester—copolymer,condensation,polymerization through ester linkage.
Q48	Why do drugs designed to cure some ailment in one organ in the body not affect the other parts? Explain with an example. Ans→ An important point about the receptors is that they are not disturbed evenly around the body. For example- heart has more β adrenergic receptors than α adrenergic receptors .This means that a drug designed to interact with β adrenergic receptors will act on heart rather than a tissue which are rich in α adrenergic receptors .
Q49	Define the following terms with one example(Any two) (a) Antipyretics (b) Antioxidants (c) Antifertility drugs Ans→ Antipyretics—The chemical substances used to bring down the body temperature are called antipyretics.Paracetamol.Phenacetin, Analgin. Antioxidants--The substance which when added to the fat and fat containing foods prevents their oxidation and thus prolongs their life.Withoutthem,fatty foods such as potato chips can not be stored for long time. Examples—Butylatedhydroxyanisol(BHA), Butylatedhydroxy toluene (BHT), Propyl gallate(PG),Tertiary butyl hydroquinone(TBHQ), Antifertility drugs—The chemicals which are used to control pregnancy are called antifertility drugs.They are mostly hormonal contraceptives and are available for females only.They are gonadal steroids(Oestrgen and Progesteron).
Q50	Account for the followings: (a) The use of aspartame is limited to cold foods and drinks. (b) Synthetic detergents are called soapless soaps. (c) Medicines should not be taken without consulting doctors. Ans→(a) It decomposes on heating. It nearly 100 times as sweet as cane sugar.Chemically it is methyl ester of dipeptide of Aspartic acid and phenylalanine. (b) Synthetic detergents are sodium compounds of benzene sulphonic acids whereas soaps are sodium compounds of higher fatty acids.Soaps are based on oils. Synthetic detergents are based on hydrocarbons. (c) Medicines should not be taken without consulting doctors because their wrong choice and over dose can cause havoc and may even prove to be fatal.