Chemistry Practice Test PDF

# PRACTICE TEST ## Time allowed: 45 Minutes ## Marks: 35 ### (i) The atomic number of an element is 35. What is the total number of electrons present in all the p orbitals of the ground state atom of that element: * (A) 17 * (B) 11 * (C) 23 * (D) 6 ### (ii) The value of magnetic quantum number...

# PRACTICE TEST ## Time allowed: 45 Minutes ## Marks: 35 ### (i) The atomic number of an element is 35. What is the total number of electrons present in all the p orbitals of the ground state atom of that element: * (A) 17 * (B) 11 * (C) 23 * (D) 6 ### (ii) The value of magnetic quantum number which gives us information about the number of orbitals is determined by: * (A) 2l - 1 * (B) 2(2l + 1) * (C) 2n + 1 * (D) 2l + 1 ### (iii) Which one of the following is not isoelectronic pair? * (A) Mg2+, Be2+ * (B) N3-, O2- * (C) N2-, O2- * (D) F-, Al3+ ### (iv) Which of the following is not permissible? * (A) n = 4, l = 3, m = 0 * (B) n = 4, l = 2, m = 1 * (C) n = 4, l = 4, m = 1 * (D) n = 4, l = 0, m = 0 ### (v) What is the value of (n + l) for the 3d subshell: * (A) 3 * (B) 5 * (C) 4 * (D) 6 ### (vi) Ionization energy for Mg → Mg+ + 1e has ΔH: * (A) 738 kJ mol-1 * (B) 238 kJ mol-1 * (C) 448 kJ mol-1 * (D) 138 kJ mol-1 ### (vii) Which element has highest ionization potential? * (A) Li * (B) Be * (C) B * (D) C ## SHORT QUESTIONS (3×5 = 15) ### (i) How two electron of 2px obey Pauli's exclusion principle in O? OR ### What is the difference between orbit and orbital? ### (ii) Arrange the orbitals of an atom from 4s to 7s according to (n + l) rule. OR ### How mass of electron can be calculated from e/m ratio and charge? ### (iii) Why 4s is orbital lower in energy than 3d orbital? OR ### State Heisenberg's uncertainty principle and Hund's rule. ### (iv) Write electronic configuration of 25Mn2+, 30Zn2+, 64Cd3+ and 13Al3+. OR ### What is the cause of greater stability of exactly half-filled and completely filled configurations? ### (v) Bohr's model says that the angular momentum of moving electron is quantized. What do you mean by this? OR ### Second I.E value is always higher than first I.E value. Justify ## LONG QUESTIONS (6+7 = 13) ### 1) Explain quantum numbers in detail. OR ### What is mass spectrometry explain its working and tell how the data is analyzed? ### 2) Explain ionization energy trends in the periodic table with justifications of these trends and anomalies. OR ### Explore the practical applications of atomic emission spectroscopy. # PRACTICE TEST ### (i) Which of the following molecules has zero dipole moment? * (A) NH3 * (B) CHCl3 * (C) H2O * (D) BF3 ### (ii) Which of the following species has unpaired electrons in anti-bonding molecular orbitals: * (A) O2 * (B) N2 * (C) B2 * (D) F2 ### (iii) Coordinate covalent bond is present in: * (A) H2O * (B) NH3 * (C) CH4 * (D) H3O+ ### (iv) Which of the following have maximum bond dissociation energy: * (A) F2 * (B) Cl2 * (C) Br2 * (D) I2 ### (v) In the formulation of N2 from N2, the electron is removed from: * (A) σ2px orbital * (B) σ*2px orbital * (C) π2p orbital * (D) π*2p orbital ### (vi) The geometry of PFs molecules is: * (A) Planar * (B) Square planar * (C) Trigonal bipyramidal * (D) Tetrahedral ### (vii) sp³ hybridization is important in describing the bonding in: * (A) NH4+ * (B) CCl4 * (C) H3O+ * (D) AgCl ## SHORT QUESTIONS (3x5 = 15) ### (i) What are the limitations of VBT? OR ### Bond angle in NF3 (102°) is less than in NH3 (107.5°). Justify. ### (ii) Why pi (π) bonds are more diffused than sigma (σ) bonds? OR ### Why ice is less dense than water? ### (iii) O2 is paramagnetic and N2 is diamagnetic nature". How can you justify this statement by using molecular orbital theory? OR ### Tetrachloromethane, CCl4, is a non-polar molecule. Draw a diagram to show the shape of this molecule. Explain why this molecule is non-polar. ### (iv) Explain the geometries of PbCl2 & SO3 on the basis of VSEPR theory. OR ### Why is the energy of σ2px orbital higher than that of 2py & π2pz orbitals in the molecule orbital diagram of N2? ### (v) Explain why hydrogen selenide, H2Se, has a higher boiling point than hydrogen sulphide, H2S. OR ### Draw a dot-and-cross diagram for xenon tetrafluoride, XeF4. ## LONG QUESTIONS (6+7 = 13) ### 1) Describe the differences between molecular orbital theory and valence bond theory. OR ### Write important postulates of valence bond theory. How bonding can be explained in oxygen and nitrogen molecule with respect to valence bond theory? ### 2) Explain paramagnetic and diamagnetic behavior of O2, O2- and O2 using molecular orbital theory? OR ### Explain the hybridization plan in CH≡CH and CH2 = CH2. # PRACTICE TEST ## Time allowed: 45 Minutes ## Marks: 35 ### (i) What is the mass of aluminium in 204 g of the aluminium oxide, Al2O3? * (A) 26 g * (B) 27 g * (C) 54 g * (D) 108 g ### (ii) If four moles of SO2 are oxidized to SO3, how many moles of oxygen molecules are required. * (A) 0.5 * (B) 1.0 * (C) 1.5 * (D) 2.0 ### (iii) The Avogadro's constant is the number of: * (A) Atoms in 1g of Helium * (B) Molecules in 35.5g of Chloride * (C) Electrons needed to deposit 24g of Mg * (D) Atoms in 24g of Mg ### (iv) How many moles of oxygen are needed for complete combustion of two moles of butane (C4H10)? * (A) 2 * (B) 8 * (C) 10 * (D) 13 ### (v) Maximum number of molecules will be in: * (A) 1 g of H2 * (B) 10 g of H2 * (C) 22 g of O2 * (D) 44 g of CO2 ### (vi) The weight of a single atom of oxygen is: * (A) 5.057 x 10-23 g * (B) 1.556 × 10-23 g * (C) 2.656 × 10-23 g * (D) 4.538 x 10-23 g ### (vii) A mixture of 8 g of H2 with 8 g of O2 is ignited 2H2 + O2 →2H2O. what is the mass of water formed? * (A) 9 g * (B) 36 g * (C) 16 g * (D) 72 g ## SHORT QUESTIONS (3×5 - 15) ### (i) Calculate moles of chlorine atoms are 0.822 gram of C2H4Cl2. OR ### Concept of limiting reactant is not applicable to the reversible reactions. Explain. ### (ii) Define Limiting reactant. How it can be identified? OR ### One mole of H2SO4 should completely react with two moles of NaOH. How does Avogadro's number help to explain it? ### (iii) Prove that one mole of each N2, CO2 and H2 contains equal number of molecules. OR ### Calculate the weight of oxygen gas evolved when 5.0g of KClO3 are completely decomposed thermally. ### (iv) Calculate the number of water molecules in 10 g of ice. OR ### The actual yield is lesser than the theoretical yield. Give reasons. ### (v) Calculate the mass in kilograms of 2.6 x 1023 molecules of SO2. OR ### What is number of H+ ions in 10 g of H3PO4? ## LONG QUESTIONS (6+7 = 13) ### 1) Differentiate between limiting and non-limiting reactants. Calculate the mass of NH3 produced when 100 g Ca(OH)2 is reacted with 100 g NH4CL. Ca(OH)2 + 2NH4Cl → CaCl2 + 2NH3 + 2H2O OR ### Aluminium reacts with bromine to form Aluminium bromide, as shown by the balanced chemical equation, 2Al + 3Br22AlBr3 If 15.8 g Al and 55.6g of Br2 are available for reaction, then determine: (a) The limiting reactant (b) The mass of AlBr3 produced ### 2) Calculate the following in 10g of NH3 at STP (Molar masses: N = 14, H = 1 gm/mol): i. Number of moles ii. Number of molecules iii. Volume in dm³ OR ### The liquid CHBr3 has a density of 2.89 g dm³. What volume of this liquid should be measured to contain a total of 4.8 x 1024 molecules of CHBr3? # PRACTICE TEST ## Time allowed: 45 Minutes ## Marks: 35 ### (i) Amount of heat absorbed when one mole of a solid melts into liquid at its melting point is called: * (A) Molar heat of sublimation * (B) Heat of vaporization * (C) Latent heat of fusion * (D) Molar heat of fusion ### (ii) Which has least vapour pressure? * (A) Ethanol * (B) Acetone * (C) Acetic acid * (D) Water ### (iii) Vapour pressure is affected by: * (A) Size of the molecules * (B) Temperature * (C) Inter molecules forces * (D) All of these ### (iv) In which of the following hydrogen bonding is not present? * (A) Water * (B) ether * (C) Ethanol * (D) Ammonia ### (v) Surface tension of a liquid is directly related to the strength of inter molecular force of attraction. Indicate the one with lowest surface tension among the following: * (A) Benzene * (B) Water * (C) Methanol * (D) Ethanol ### (vi) Which of the following has highest value of surface tension? * (A) H2O * (B) C5H12 * (C) C6H12 * (D) C7H16 ### (vii) The boiling points of NH3, H2 and HF decrease in the order: * (A) HF > NH3> H2O * (B) H2O > NH3> HF * (C) H2O > HF > NH3 * (D) HF > H2O > NH3 ## SHORT QUESTIONS (3×5 = 15) ### (i) In a Pressure cooker, food can be cooked quickly, as compared to the simple cooker, Give reason. OR ### Why water is a liquid and H2S is a gas at room temperature? ### (ii) Describe vacuum distillation, giving its one application. OR ### Explain why Evaporation is a cooling process ### (iii) Briefly explain why the climate near large water bodies is moderate than interior of the land? OR ### Why distillation under reduced pressure is often used in the purification of chemicals? ### (iv) Why temperature of a boiling liquid does not raise at its boiling point? OR ### Why ethane (C2H6) is a gas whereas C6H14 hexane is liquid at STP? ### (v) Ice floats on water. Justify it. OR ### Evaporation takes place at all temperatures. Justify. ## LONG QUESTIONS (6+7 = 13) ### 1) Define boiling point. How will you explain the two practical applications regarding the effect of pressure on the boiling point of a liquid? OR ### What are London Dispersion forces? Also discuss the factors affecting these forces. ### 2) Define hydrogen bonding. Explain hydrogen bonding with at least three examples. OR ### Use the concept of hydrogen bonding to explain the following properties of water? i. High surface tension ii. High heat of vaporization # PRACTICE TEST ## Time allowed: 45 Minutes ## Marks: 35 ### (i) The enthalpy of formation of CO2 is -394 kJmol¹. The enthalpy change for the reaction. 2CO2(g) → 2C(s) + 2O2(g) is: * (A) + 92kJ * (B) + 788kJ * (C) + 184kJ * (D) + 23kJ ### (ii) Born-Haber cycle is a special application of: * (A) Hess's law * (B) Rate law * (C) Boyle's law * (D) Henry's law ### (iii) For an endothermic reaction the energy of product is: * (A) Equal to that of reactant * (B) Equal to the energy of activation * (C) Higher than that of reactants * (D) Lower than that of reactants ### (iv) The standard enthalpy of formation is zero for: * (A) C6H12O6 * (B) O2 * (C) N2O * (D) NaCl ### (v) In a bomb calorimeter, the reactions are carried out at constant: * (A) pressure * (B) temperature * (C) volume * (D) none of above ### (vi) A spontaneous change is one in which the system suffers: * (A) an increase in internal energy * (B) lowering in entropy * (C) lowering in free energy * (D) no energy change ### (vii) 1 J is equivalent to: * (A) 0.4184 cal * (B) 4.18 cal * (C) 0.239 cal * (D) 0.39 cal ## SHORT QUESTIONS (3x5 = 15) ### (i) Give two definitions of Lattice Energy with an example in each case. OR ### Justify that heat of formation of compound is sum of all the other enthalpies. ### (ii) Comment that enthalpy of neutralization is merely the heat of formation of one mole of liquid water. OR ### Differentiate between internal energy and enthalpy. ### (iii) What is Born Haber cycle? Draw a labelled Born-Haber cycle for the formation of NaCl. OR ### State Hess's law and give one example. ### (iv) Differentiate between constant pressure and constant volume calorimetry. OR ### Define enthalpy of atomization, enthalpy of solution, enthalpy of neutralization. ### (v) What is the internal energy of a system? Justify that internal energy is a state function. OR ### Describe the difference between heat capacity and molar heat capacity. ## LONG QUESTIONS (6+7 = 13) ### 1) Hydrochloric acid is neutralized with sodium hydroxide in the following reaction: HCl + NaOH → NaCl + H2O ΔΗ = -57.68 KJ/mol In a coffee cup calorimeter 100cm³ of 1M HCl and 100 cm³ of 1M NaOH are mixed 24.6°C. What is the final temperature of a mixture? Assume that density of both solution is 1.00 g/ml and heat capacity of water is 4.08 J/g°C. OR Methane is the major substance in natural gas. How much heat is released when 20g of methane burns in excess of air under standard conditions? The standard enthalpies of CO2, H2O and CH4 are -393.5kJ mol¹, 285.8kJ mol¹ and 74.6kJ mol respectively. ### 2) Define Hess's law of constant heat summation with two examples. OR Define the following terms with examples: i. State function ii. Heat Capacity iii. Enthalpy of substance # PRACTICE TEST ## Time allowed: 45 Minutes ## Marks: 35 ### (i) The rate constant is equal to the rate of reaction if the order of reaction is: * (A) 0 * (B) 1 * (C) 2 * (D) 3 ### (ii) The rate of a chemical reaction is measured in: * (A) mol.dm³.s-1 * (B) mol.dm³.s * (C) mol.dm³.s * (D) dm³.mol-1.s-1 ### (iii) The units of rate constant and the rate of reaction will be the same when order of reaction is: * (A) 2 * (B) 3 * (C) 0 * (D) 1 ### (iv) When concentration of a reactant is double, the rate of reaction becomes half. The order of reaction with respect to that substance is: * (A) 0 * (B) 1/2 * (C) -1 * (D) 1 ### (v) If the rate of decay of a radioactive isotope decreases from 200 counts per minutes to 25 counts per minute after 24 hours. What is half life? * (A) 3 hours * (B) 4 hours * (C) 6 hours * (D) 8 hours ### (vi) Which change will never happen in a catalyst during reaction? * (A) Appearance * (B) Chemical composition * (C) Surface area * (D) Physical state ### (vii) The order of reaction CH3COOC2H5 + H2O → CH3COOH + C2H5OH * (A) Pseudo first * (B) Two * (C) Three * (d) Zero ## SHORT QUESTIONS (3x5 = 15) ### (i) What is the effect of catalyst on the following? (a) The rate reaction (b) The energy of activation (c) The equilibrium position of a reversible reaction OR ### Define the following: (a) Average rate of reaction (b) Instantaneous rate of reaction (c) Order of reaction ### (ii) What is Arrhenius equation? How this equation described the effect of increase in temperature on the rate constant and rate of a reaction? OR ### Differentiate between homogeneous and heterogeneous catalysis, giving one example of each. ### (iii) The reaction given below is first order in H: H2(g) + Br2(g)→2HBr (g) Write rate equation (rate law) of the reaction and deduce overall order of reaction. OR ### Indicate the Slow step (b) Determine the order of reaction (c) Write overall reaction, with the help of the information given below: Rate = k[NO2]² Step 1: NO2(g) + NO2(g) →NO3(g) +NO(g) Step 2: NO 3(g) + CO(g) →NO2 +CO (g) ### (iv) What is Arrhenius equation? How this equation describes the effect of increases in temperature on the rate constant and rate of a reaction? OR ### Which of the following reactions will show high rate of reaction? Also give reason. Zn(s) + 2HCl(aq) → ZnCl2(aq) +H2(g) (Zninpowdered form) OR Zn(s) + 2HCl(aq)→ZnCl2(aq) +H2(g) (Znin form of bigpieces) ### (v) How the mechanism of a chemical reaction can help to point out the rate-determining step? OR ### What is a first order reaction? Give two examples. ## LONG QUESTIONS (6+7 = 13) ### 1) Discuss the effect of change in concentration of reactants and the change in surface area of the reactants on the rate of reaction. OR ### Explain collision theory of reaction rates with reference to activation energy, formation of activated complex and enthalpy changes in a chemical reaction. ### 2) Define enzymes? Give two examples in which enzymes act as catalyst. OR ### Explain the effects of concentration, temperature and surface area on reaction rates. # PRACTICE TEST ## Time allowed: 45 Minutes ## Marks: 35 ### (i) Kc is Independent of: * (A) Temperature * (B) Pressure * (C) Both temperature and pressure * (D) Kp ### (ii) The most favorable conditions for the manufacture of NH3 is: * (A) high temperature and high pressure * (B) high temperature and low pressure * (C) low temperature and low pressure * (D) low temperature and high pressure ### (iii) What happens if pressure is applied to the equilibrium Ice ↔ Water? * (A) More amount of water is formed * (B) More amount of ice is formed * (C) Water changes to vapours * (D) No change ### (iv) The chemical equilibrium of a reversible reaction is not influenced by: * (A) catalyst * (B) temperature * (C) pressure * (D) concentration ### (v) Which of the following relationship is incorrect * (A) Kp =Kc when Δη = 0 * (B) Kp <kc when An<0 * (C) Kp > Kc whenAn>0. * (D) KcKc when An=0 ### (vi) For the reaction, H2(g) + 12(g) 2HI(g) the equilibrium constant "K," changes with * (A) total pressure * (B) catalyst * (C) amounts of H2 and 12 taken * (D) temperature ### (vii) For the following reaction: 2A(g) + B(g) 3C(g) We can write: * (A) Kc > Kp * (B) Kc < Kp * (C) Kp - Kc = 0 * (D) Kp - Kc = -1 ## SHORT QUESTIONS (3×5 = 15) ### (i) Write any four important features of equilibrium constant. OR ### What will be the effect of change in pressure on ammonia (NH3) synthesis? ### (ii) Differentiate between reversible and irreversible reactions with examples. OR ### Differentiate between homogeneous and heterogeneous equilibria. ### (iii) Consider the following reaction: N2(g) + O2(g)2NO (g) Kc = 0.1 at 2000°C If original concentrations of N₂ and O2 were 0.1M each. Calculate the concentration of NO at equilibrium. OR ### Consider the following equilibrium 2I(g) 12(g) What would be the effect on the position of equilibrium when temperature is deceased? ### (iv) What are K, and K. How they can be related to each other? OR ### Explain the effect of addition of catalyst on equilibrium. ### (v) Describe the effect of increase in pressure and temperature on the following reaction at equilibrium: 25O2(g) + O2(g): 2SO3(g)∆H = -198 kJmol¹ OR ### Write Kc and Kp expressions for each of the following reactions. i. FeO(s) + CO(g) - Fe(s) + CO2(g) ii. P4(s) + 502(g) - P4010(s) lil. CH4(g) + 4Cl2(g) - CCl4(g) + 4HCl(g) ## LONG QUESTIONS (6+7 = 13) ### 1) Discuss physical and chemical method for determining the value of Kc. OR ### What is solubility product? Give its applications for any two precipitation reactions. ### 2) State Le-Chatelier's principle. Explain the effect of change in temperature and pressure on equilibrium for Contact's process. OR ### What is Le-Chateller's principle? Describe three major steps which could be taken in order to get maximum yield of NH3 In Haber's process. # PRACTICE TEST ## Time allowed: 45 Minutes ## Marks: 35 ### (i) Water cannot act as: * (A) Lewis acid * (B) Lewis base * (C) Bronsted acid * (D) Bronsted base ### (ii) The pH of human blood is: * (A) 3.5 * (8) 5.35 * (C) 7.35 * (D) 8.35 ### (iii) Strength of an acid is determined from the value of: * (A) Kw * (B) Kc * (C) Ka * (D) Kp ### (iv) A buffer solution contains 0.1 mol dm³ of CH3COOH and CH3COONa each. pk, for acetic acid is 4.76. What is the pH of buffer? * (A) 4.76 * (B)-4.76 * (C) 9.24 * (D) 9.52 ### (v) pH of 0.001 M NaOH solution is: * (A) 10-3 * (B) 11 * (C) 10-11 * (D) 3 ### (vi) Which of the following is an amphoteric oxide? * (A) MgO * (B) Cr2O3 * (C) NO2 * (D) Na2O ### (vii) Which salt will form acidic solution in water? * (A) K2CO3 * (B) KCL * (C) NaBr * (D) NH4Cl ## SHORT QUESTIONS (3×5 = 15) ### (i) Define pH. How it can be related with pOH and pkw. What are the values of pH for acidic, basic and neutral solutions? OR ### An aqueous solution contains 1.0 × 10-9 moles/dm³ of hydronium ions. Calculate the pOH of these solutions. ### (ii) What is the percentage ionization of acetic acid in a solution in which 0.1M of it has been dissolved per dm³ of the solution? (Ka=1.8 x 10-5) OR ### What is acid ionization constant? How it can be related to pk, and can be used to measure the strength of an acid? ### (iii) Define water dissociation constant. What is the effect of temperature on the value of Kw? OR ### Explain conjugate acids and bases. Give conjugate acids for NH3 & OH- and bases for NH+ 4 & HCl? ### (iv) Explain conjugate acids and bases. Give conjugate acids for NH3 & OH- and bases for NH+ 4 & HCI? OR ### Define water dissociation constant. What is the effect of temperature on the value of Kw? ### (v) What is acid ionization constant? How it can be related to pk, and can be used to measure the strength of an acid? OR ### Define pH. How it can be related with pOH and pKw. What are the values of pH for acidic, basic and neutral solutions? ## LONG QUESTIONS (6+7 = 13) ### 1) Define ionic product of water and derive its expression. Also explain how pH and pOH in aqueous medium can be calculated using Kw? OR ### Explain how the mixture of CH3COOH and CH3COONa acts as a buffer. Also calculate the pH of a buffer containing 0.1 M CH3COOH and 1.0 M CH3COONa. The value of PKa for CH3COOH is 4.76. ### 2) What are buffer solutions? Elaborate with suitable examples. Also describe different types of buffers. OR ### Define ionic product of water. Prove mathematically pKa + pKb=14. # PRACTICE TEST ## Time allowed: 45 Minutes ## Marks: 35 ### (i) Carbon forms a large number of compounds because it has the unique property of; * (a) Isomerism * (b) Complexity of organic compounds * (c) Catenation * (d) Covalent nature ### (ii) Which of the following type of coal has maximum %age of carbon? * (a) Peat * (b) Lignite * (c) Anthracite * (d) Bituminous ### (lil) -SH is a functional group of which class of organic compounds? * (a) Ether * (b) Thioalcohol * (c) Aldehyde * (d) Carboxylic acid ### (iv) A nucleophile is: * (a) Electron-rich species * (b) A Lewis acid * (c) Electron-deficient species * (d) Positively charged species ### (v) How many isomers are possible for C2H6O? * (a) 2 * (b) 4 * (c) 8 * (d) 5 ### (vi) Ethanol and dimethyl ether are __ isomers of one another: * (a) Chain * (b) Position * (c) Functional Group * (d) Metamers ### (vii) The common name of butanoic acid is: * (a) Oxalic acid * (b) Valeric acid * (c) Malonic acid * (d) Succinic Acid ## SHORT QUESTIONS (3x5 = 15) ### (i) What is functional group? Give its three examples. OR ### How vital force theory was rejected by Wohler? ### (ii) Write down three reasons which give the importance of functional groups for the organic compounds. OR ### Give IUPAC names of the following: Glutaric acid Acyl chloride Methyl formate ### (iii) Define tautomerism with example. OR ### What are elimination reactions? Give example. ### (iv) Differentiate between hydrolysis and hydration. OR ### An organic compound has empirical formula 'CH' and molecular mass 78 amu. Calculate its molecular formula. ### (v) Draw displayed and skeletal formula of the following: Ethanol 2,2-dimethylpropane OR ### Write characteristics of homologous series. ## LONG QUESTIONS (6+7 = 13) ### 1) Explain free radical substitution reactions of alkanes taking an example of methane. OR ### Give systematic names to the following compounds. (CH3)2CHCH(Br)CH2CH3 CH3CH(CH3)CH2CH(OH)CH3 CH3CH(OH)CH2CH3 CH3CH = C(OH)CH3 CH3CH(OH)CH2CH3 CH3CH(OH)CH(Br)CH3 ### 2) Explain the following: Types of reagents used in chemical reactions Types of bond breakage in chemical reactions OR ### What is structural isomerism? Explain functional group and tautomerism with examples.