TABLE OF CONTENTS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 2 TOPIC PAGE CHEMISTRY – DK024 Chapter 1 – Reaction Kinetics 3 Chapter 2 – Thermochemistry 13 Chapter 3 – Electrochemistry 27 Chapter 4 – Introduction to Organic Chemistry 37 Chapter 5 – Alkanes 55 Chapter 6 – Alkenes 65 Chapter 7 – Benzene and its Derivatives 79 Chapter 8 – Alcohols 87 Chapter 9 – Carbonyl Compounds 104 Chapter 10 – Carboxylic acids 116 DK024 Past Paper Collections PSPM DK024 2022/2023 128 PSPM DK024 2021/2022 134 PSPM DK024 2020/2021 141 PSPM DK024 2019/2020 148 ACKNOWLEDGEMENT
CHAPTER 1 REACTION KINETICS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 3 CHAPTER 1 REACTION KINETICS
CHAPTER 1 REACTION KINETICS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 4 SUBJECTIVE PRACTICES 1. a) Define reaction rate. b) Write the differential rate equation for the following reactions: i. I − (aq) + OCl− (aq) → Cl− (aq) + OI− (aq) ii. 3O2 (g) → 2O3 (g) iii. 4NH3 (g) + 5O2 (g) → 4NO (g) + 6H2O (g) iv. N2 (g) + 3H2 (g) → 2NH3 (g) ANSWER a) Reaction rate is the change in the concentration of a reactant or a product with time. b) i d I d OCl d Cl d OI [ ] [ ] [ ] [ ] Rate dt dt dt dt − − − − = − = − = + = + ii 2 3 1 1 [ ] [ ] 3 2 d O d O Rate dt dt = − = + iii 3 2 2 1 1 1 [ ] 1 [ ] [ ] [ ] 4 5 4 6 d NH d O d H O d NO Rate dt dt dt dt = − = − = + = + iv 2 2 3 [ ] [ ] 1 1 [ ] 3 2 d N d H d NH Rate dt dt dt = − = − = + 2. For the reaction R → P, the concentration of a reactant changes from 0.03 M to 0.02 M in 25 minutes. Calculate the average rate of reaction using units of time both in minutes and seconds. ANSWER 6 1 [ ] 0.02 0.03 (25 60) 6.67 10 R Average rate of reaction t s Ms − − = − = = −
CHAPTER 1 REACTION KINETICS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 5 3. Ethane, C2H6 can be converted to butane, C4H12 through dimerization. Using the graph below, determine the average rate of reaction from t = 2000 seconds until t = 6000 seconds and the instantaneous rate at 4500 seconds. 226 → 412 ANSWER 4 12 6 1 [ ] 0.0110 0.0020 (6000 2000) 2.25 10 C H Average rate of reaction t s Ms − − = − = − = 4 12 6 1 6 1 [ ] tan 0.00680 4500 1.51 10 ( :1.51 1.55 10 ) C H Ins taeous rate time M s Ms range to Ms − − − − = = = Slope for average rate Concentration for instantaneous rate
CHAPTER 1 REACTION KINETICS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 6 4. a) Explain the following terms: i. rate law ii. rate constant ANSWER i) An equation that relates the rate of a reaction to the rate constant, k and concentration of the reactants raised to some powers. ii) The proportionality constant in the equation that expresses the relationship between the rate of a chemical reaction and the concentrations of the reacting substances. b) Consider the reaction as zero, first and second order reaction, → i. Write the rate law. ii. Determine the unit of rate constant. ANSWER i) ( ) ( ) ( ) 2 1 0 [ ] [ ] 2 st nd order order rate k order rate k A rate k A = = = ii) ( ) ( ) ( ) 1 1 1 1 1 0 2 st nd k s order k M s order k Ms order − − − − = = = 5. Consider the reaction: 2 2 3 N g H g NH g ( ) 3 ( ) 2 ( ) + → Supposed that at a particular moment during the reaction, molecule of hydrogen is reacting at the rate of 0.074 M s–1 . Calculate the rate of: a) formation of ammonia b) depletion of nitrogen ANSWER a) 2 2 3 [ ] [ ] 1 1 [ ] 3 2 d N d H d NH Rate dt dt dt = − = − = + 3 2 3 2 1 1 3 1 1 [ ] [ ] , 2 3 [ ] 2 [ ] 3 2 0.074 3 0.049 d NH d H from the equation dt dt d NH d H dt dt Ms rate of formation NH Ms − − + = − = = =
CHAPTER 1 REACTION KINETICS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 7 b) 2 2 3 [ ] [ ] 1 1 [ ] 3 2 d N d H d NH Rate dt dt dt = − = − = + 2 2 2 2 1 1 2 [ ] [ ] 1 , 3 [ ] [ ] 1 3 1 0.074 3 0.025 d N d H from the equation dt dt d N d H dt dt Ms rate of depletion N Ms − − − = − = = = 6. The data below were obtained from the following reaction at 27oC. 3()3 + → 3()3 + Exp. [CH3CH(Cl)CH3] / M [NaOH] / M Reaction rate / M min−1 1 0.15 0.25 3.0 ⋅ 10-3 2 0.15 0.50 6.0 ⋅ 10-3 3 0.45 0.25 9.0 ⋅ 10-3 a) What is the order with respect to each reactant? b) Write the rate equation. ANSWER a) [ ] [ ] 3 3 ( ) x y Rate k CH CH Cl CH NaOH = ( ) ( ) 3 3 3 3 3 3 1 : 2 [ ] [ ] [ ] [ ] 3.0 10 [0.15] [0.25] 6.0 10 [0.15] [0.50] 1 1 2 2 1 x y x y x y x y y Exp Exp rate k CH CH Cl CH NaOH rate k CH CH Cl CH NaOH k k y first order of reaction with respect to NaOH − − = = = = ( ) ( ) ( ) 3 3 3 3 3 3 3 3 1 : 3 [ ] [ ] [ ] [ ] 3.0 10 [0.15] [0.25] 9.0 10 [0.45] [0.25] 1 1 3 3 1 x y x y x y x y x Exp Exp rate k CH CH Cl CH NaOH rate k CH CH Cl CH NaOH k k x first order of reaction with respect to CH CH Cl CH − − = = = = b) Rate k CH CH Cl CH NaOH = [ ][ ] 3 3 ( )
CHAPTER 1 REACTION KINETICS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 8 7. The reaction of nitric oxide with hydrogen at 1280 °C is: 2 2 2 2 ( ) 2 ( ) ( ) 2 ( ) NO g H g N g H O l + → + The following data was collected at this temperature: Experiment [NO] / M [H2] / M Initial rate / M s−1 1 5.00 × 10−3 2.00 × 10−3 1.25 × 10−5 2 10.00 × 10−3 2.00 × 10−3 5.00 × 10−5 3 10.00 × 10−3 4.00 × 10−3 10.00 × 10−5 Based on the data, determine: a) The rate law. b) The rate constant. ANSWER a) 2 [ ] [ ] x y Rate k NO H = 2 2 5 3 3 5 3 3 1 : 2 [ ] [ ] [ ] [ ] 1.25 10 [5.00 10 ] [2.00 10 ] 5.00 10 [10.00 10 ] [2.00 10 ] 1 1 4 2 2 second x y x y x y x y x Exp Exp rate k NO H rate k NO H k k x order of reaction with respect to NO − − − − − − = = = = 2 2 5 3 3 5 3 3 2 2 : 3 [ ] [ ] [ ] [ ] 5.00 10 [10.00 10 ] [2.00 10 ] 10.00 10 [10.00 10 ] [4.00 10 ] 1 1 2 2 1 x y x y x y x y y Exp Exp rate k NO H rate k NO H k k y first order of reaction with respect to H − − − − − − = = = = 2 2 : [ ] [ ] Rate Law Rate k NO H = b) 2 2 5 3 2 3 2 1 [ ] [ ] 10.00 10 [10.00 10 ] [4.00 10 ] 250 Rate k NO H k M s − − − − − = = =
CHAPTER 1 REACTION KINETICS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 9 8. a) What is meant by activation energy? b) State two requirements for effective collisions. c) Give two factors that affect the rate of reaction for chemical reaction. Explain your answers. ANSWER a) The minimum amount of energy required to initiate a chemical reaction. b) • Colliding molecules must possess a minimum amount of energy called activation energy. • Collision must be in correct orientation in order to form products. 9. The following equation shows the decomposition of NH3: 1 3 2 2 2 ( ) 3 ( ) ( ) 92.2 Fe NH g H g N g H kJmol − + = + a) The above reaction is catalysed by iron. What is the function of iron? b) Draw and label the potential energy profile for the reaction with and without iron. ANSWER a) Fe - as a catalyst to increase the reaction rate by providing an alternative pathway with lower activation energy. b)
CHAPTER 1 REACTION KINETICS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 10 MCQ PRACTICES 1. What is rate of reaction? A How fast the reaction is. B How loud the reaction is. C How big a reaction is. D How much gas a reaction produces. 2. Which of the following is a unit of rate of reaction? A s -1 B Ms-1 C M D M-1 s -1 3. Instantaneous rate of change means the same thing as: A slope of the tangent line. B slope of the normal line. C slope of the secant line. D slope of the linear line. 4. A scientist conducts an experiment to determine the rate of the following reaction: 2 2 N O NO + → 2 If the initial concentration of N2 was 0.500M and the concentration of N2 was 0.450M after 0.100 s, what is the rate of the reaction? A 5.00 M/s B 1.00 M/s C 0.50 M/s D 0.25 M/s 5. What are the units of k for the rate law: Rate = k[A][B]2 when the concentration unit is mol/L? A Ms-1 B M C M-1 s -1 D M-2 s -1 6. Given the following data for this reaction: NH aq NO aq N g H O l 4 2 2 2 ( ) ( ) ( ) 2 ( ) + − + → + Exp. [NH4 + ] / M [NO2 - ] / M Rate / Ms-1 1 0.010 0.020 0.020 2 0.015 0.020 0.030 3 0.010 0.010 0.005 The rate law for the reaction is: A Rate = k[NH4 + ][NO2 - ] B Rate = k[NH4 + ] 2 [NO2 - ] 2 C Rate = k[NH4 + ] 2 [NO2 - ] D Rate = k[NH4 + ][NO2 - ] 2 7. The rate constant of a reaction is k = 3.28 × 10-4 s -1 . Find the order of the reaction. A Zero order B First order C Second order D Third order 8. The collision theory of reaction rates: I. Helps to expose how temperature affects the rate. II. Assumes that the rate depends on the frequency at which reactants collide. III. Assumes that reactants must be in correct orientation to react. IV. Assumes that only collisions with energy above the activation energy are successful. A I, II, and III are correct. B I, III, and IV are correct. C II, III, and IV are correct. D All are correct statements.
CHAPTER 1 REACTION KINETICS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 11 9. The rate law for the iodine clock reaction is given by: Rate = k[IO3 - ][I- ] 2 [H+ ] 2 . Which of the following statement below is correct: A This reaction is first order with respect to IO3 - and third order overall. B This reaction is second order with respect to Iand third order overall. C This reaction is first order with respect to IO3 - and fifth order overall. D This reaction is third order with respect to H+ . 10. In an endothermic reaction the products have A More energy than the reactants. B Less energy than the reactants. C The same energy as the reactants. D No energy. 11. Which of the following factors cannot affect the rate of a chemical reaction? A Temperature B Catalyst C Size of container D Concentration 12. Catalyst is a substance, which __________. A increases the speed of a reaction. B decreases the kinetic energy of particles. C increase the Activation Energy, Ea. D alters the value of equilibrium constant in a reversible. 13. What is the unit of the rate constant (k) for a first-order reaction? A M/s B L/mol C s -1 D J/mol 14. What is the purpose of the rate law in a chemical reaction? A It describes the stoichiometry of the reaction. B It relates the rate to the concentration of reactants. C It predicts the time at which the reaction will reach completion. D It explains the effect of temperature on the reaction. 15. In a chemical reaction, what is the measure of "Δ[A]/Δt" used to represent in the rate equation? A The change in activation energy. B The overall energy change in the reaction. C The change in concentration of reactants or products over time. D The change in temperature during the reaction. 16. According to the rate equation, how does the rate of reaction change with time? A It remains constant throughout the reaction. B It increases as the reaction progresses. C It decreases as the reaction proceeds. D It varies depending on the type of reaction. 17. In the context of reaction rates, what does the term "activation energy" refer to? A The energy of the products. B The energy needed to initiate a reaction. C The energy released during a reaction. D The energy of the reactants. 18. Which of the following factors can influence the rate of a chemical reaction? A The colour of the reactants. B The size of the reaction vessel. C The concentration of reactants. D The presence of a precipitate.
CHAPTER 1 REACTION KINETICS Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 12 19. In an exothermic reaction the products have A More energy than the reactants. B Less energy than the reactants. C The same energy as the reactants. D No energy. 20. How is the rate of reaction typically expressed mathematically? A Rate = Δ[A] / Δt B Rate = [A] × [B] C Rate = Kc / Kp D Rate = Temperature × Pressure
CHAPTER 2 THERMOCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 13 CHAPTER 2 THERMOCHEMISTRY
CHAPTER 2 THERMOCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 14 SUBJECTIVE PRACTICES 1. The following terms are often used in thermochemistry. a) Differentiate exothermic process and endothermic process by using the energy profile diagrams. b) Explain standard enthalpy change by giving an appropriate example. ANSWER a) Exothermic reaction is the process of heat being released to the surroundings. Endothermic reaction is the process of heat being absorbed from the surroundings. b) Heat given off or absorbed during a reaction at standard state. 2. Define and write an example of thermochemical equation for each of the following terms: a) Standard enthalpy of formation b) Standard enthalpy combustion c) Standard enthalpy of neutralisation ANSWER a) Standard enthalpy of formation: The heat change when 1 mole of a compound is formed from its elements in their most stable states under standard condition (25°C and 1 atm). Example: ( ) ( ) ( ) 1 2 4 C s H g CH g H a kJ mol − + → = b) Standard enthalpy of combustion: The heat released when 1 mole of substances is burnt completely in excess oxygen under standard condition (25°C and 1 atm). Example: ( ) ( ) ( ) ( ) 1 4 2 2 2 CH g O g CO g H O l H b kJ mol 2 2 − + → + = − c) Standard enthalpy of neutralisation: The heat released when 1 mole of water, H2O, is formed from the neutralisation of an acid and a base under standard condition (25°C and 1 atm). Example: ( ) ( ) ( ) ( ) 1 2 NaOH aq HCl aq NaCl aq H O l H c kJ mol − + → + = −
CHAPTER 2 THERMOCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 15 3. Consider the following reaction: H g O g H O g H kJ 2 2 2 ( ) ½ 241.8 + → = − ( ) ( ) a) Sketch the energy profile diagram of the above reaction. b) Which enthalpy is larger: reactants or product? c) For the reaction, 2 2 H O g H g O g 2 2 2 ( ) → + ( ) ( ) What is the enthalpy change under the same condition? ANSWER a) b) Reactant c) 2 241.8 ( ) 483.6 H kJ kJ = + = + 4. The following reaction occurs at room temperature and pressure: 2 Cl g Cl g ( ) → 2 ( ) a) State which has higher enthalpy under this condition, Cl (g) or Cl2 (g) b) At a constant pressure, a complete combustion of butane, CH4 (g) releases 890.3 kJmol-1 . Write a balanced thermochemical equation for the reaction. c) Draw the energy profile diagram for the reaction. ANSWER a) Reactant, Cl b) ( ) ( ) ( ) ( ) 1 4 2 2 2 CH g O g CO g H O l H kJ mol 2 2 890.3 − + → + = − c)
CHAPTER 2 THERMOCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 16 5. Define: a) heat capacity, C b) specific heat capacity, c ANSWER a) Heat capacity, C Amount of heat (q) required to raise the temperature of a given quantity of substance by 1 K or 1oC Unit of C : JK–1 or J oC –1 b) Specific heat capacity, c Amount of heat (q) required to raise the temperature of 1 gram of a substance by 1 K or 1oC Unit of c: J g –1 K –1 or J g –1 oC –1 6. A constant volume bomb calorimeter with the heat capacity 1500 J ℃-1 is used to burn 0.1234 g of magnesium. The calorimeter was surrounded with 1000 g of water. Once the sample is burnt, the temperature of the calorimeter and water raised by 1.653 ℃. Calculate the enthalpy of combustion of magnesium in kJ mol-1 . ANSWER ( )( )( ) ( )( ) ( ) 1000 4.18 rxn water cal water water cal Heat released by combustion heat absorbed by water and calorimeter q q q m c T C T g = − = + = + = ( )( ) ( )( ) 1 1 1 -1 -3 1.65 1500 1.65 24.3 0.1234 24.3 5.078 10 o J g C C J C C Molar mass of Mg gmol Mol of Mg mol − − − + = − = = = q 9372 J rxn 5.078 x 10-3 mol of Mg combusted released 9372 J of heat. Therefore, 1 mol of Mg combusted releases: = 1845608.51 J = 1845.6 kJ ∴ ∆Hc of Mg = − 1845.6 kJmol−1
CHAPTER 2 THERMOCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 17 7. When 150 mL of 1.00 M HCl is mixed with 150 mL of 1.00 M NaOH in a Styrofoam ‘coffee-cup’ calorimeter, the temperature rose from 25.00 ℃ to 31.72 ℃. By assuming the specific heat capacity of the solution is 4.18 J g-1 ℃-1 and the density of the solution is 1 g mL-1 , determine the heat of the neutralization. ANSWER Equation for the neutralization reaction: ( ) ( ) ( ) 2 HCl aq NaOH aq NaCl aq H O l + + → ( ) 1 1.00 0.150 0.150 1 1.00 0.150 0.150 Mol of HCl used mol L L mol Mol of NaOH used mol L L mol − = = − = = Since both of HCl and NaOH are in stoichiometric proportions, Therefore, mol of H2O produced in the reaction is 0.150 mol By assuming the densities and specific heat capacities of the solution as the same as for water: Mass of HCl = mass of NaOH = 150 g ∴mass of solution = mass of HCl + mass of NaOH = (150 + 150) g = 300 g q q q rxn soln cal = + – ( ) Since the heat capacity of calorimeter is not given, it is assumed that no heat lost to calorimeter Therefore, ( ) ( )( )( ) ( )( )( ) 1 1 – 300 4.184 31.72 – 25.00 8434.944 soln soln o o o m c T g J g C C C J − − = = − = − = − q q rxn soln 0.15 mol of H2O produced from the reaction released – 8434.94 J of heat 2 , 1 : 56232.96 . Therefore mol of H O releases J − − = − = − 1 H 56 233 kJmol neut
CHAPTER 2 THERMOCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 18 8. 0.4321 g of aluminium is completely combusted in a bomb calorimeter with the heat capacity of 4.95 kJ °C-1 and the temperature rose from 24.95 oC to 28.55 oC. What is the heat of combustion of aluminium expressed in kJ mol-1 ? ANSWER 28.55 – 24.95 3.60 o o o = = T C C C ( ) 1 4.95 3.60 17.82 – cal cal o o q C T kJ C C kJ − = = = = + q q q rxn water cal Since the mass of water is not given, water is assumed as a part of the calorimeter itself Therefore, qrxn = – qcal = − 17.82 kJ 1 27.0 0.4321 27 0.016 Molar mass of Al gmol Mol of Al mol − = = = 0.016 mol Al release - 17.82 kJ of heat , 1 Al : 1113.75 c Therefore mol of releases kJ H of Al − = − = − 1113.75 -1 kJ mol 9. A cook wanted to boil 2.0 kg of water in a pot. If the initial temperature of the water is 20 oC, what is the mass of natural gas, CH4 must be burned to raise the temperature of the water to 100 oC? Assume there is no heat loss to the surrounding. [Given: Specific heat capacity of water = 4.18 J g-1 ℃-1 ; ∆H of CH4 = -890 kJ/mol] ANSWER ( )( )( ) ( )( )( ) 4 1 1 2000 4.18 100 20 668800 . rxn water water water o o o rxn Heat released by combustion of CH Heat absorbed by water q q m c T g J g C C C q J − − = − = = = − = − = −668 8 kJ ( ) 1 4 1 12.0 1.0 4 16.0 Molar mass of CH gmol gmol − − = + = 890 kJ of heat released by combustion of 16.0 g of CH4 Therefore, 668.8 kJ of heat released by combustion of 12.023 g of CH4 ∴ mass of CH4 combusted = 12.023 g
CHAPTER 2 THERMOCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 19 10. A quantity of 1.922 g of methanol (CH3OH) was burned in a constant-volume bomb calorimeter. Consequently, the temperature of the water rose by 4.20 °C. If the quantity of water surrounding the calorimeter was exactly 2000 g and the heat capacity of the calorimeter was 2.02 kJ °C-1 , calculate the molar heat of combustion of methanol. [The specific heat of water is 4.18 J g-1 ℃-1 ]. ANSWER ( ) ( )( ) ( )( ) ( ) ( ) 1 1 1 4.20 2000 4.18 4.20 35112 35.112 2.02 4.20 8.484 35.112 8.484 q m c T Cc T w w T C q g J g C C water J kJ q kJ C C cal kJ q q q rxn water cal kJ kJ − − − = = = = = = = = = − + = − + = − 43.596 kJ 1 1.922 3 32 0.060 3 0.060 43.596 3 43.596 ) , 1 ( 1 3 0.06 726.60 g Mol of CH OH gmol mol CH OH mol CH OH kJ kJ So mol CH OH mol mol kJ H − = = − − = − = −726.60 -1 kJ mol
CHAPTER 2 THERMOCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 20 11. The enthalpy of combustion of benzoic acid is -3226.7 kJ mol-1 . When 3.2 g benzoic acid, C6H5COOH is completely combusted in a bomb calorimeter containing 2.0 g of water, the temperature of the water increased by 3.8 ℃. Calculate the heat capacity of the calorimeter. [The specific heat of water is 4.18 J g-1 ℃-1 ]. ANSWER ( ) ( ) ( ) 6 5 1 1 6 5 6 5 3.2 122 0.0262 1 3226.7 3226.7 0.0262 0.026 1 84.540 rxn mass n of C H COOH Mr g gmol mol mol of C H COOH kJ mol x mol C H COOH kJ q heat absorb calorimeter heat absorb by water C − − = = = = = = = − + = − ( ) ( ) 84.540 3.8 2.0 4.18 3.8 T mc T C x x x C + = − + = 22.239 o -1 J C Heat capacity of calorimeter , C = 22.239 J oC-1
CHAPTER 2 THERMOCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 21 12. Ethanol, CH3CH2OH, is produced from fermentation of sugarcane and widely used as an alternative fuel to replace petrol. A 1.00 g sample of ethanol was burned in a bomb calorimeter, which has a total heat capacity of 11.0 kJ ℃-1 . The temperature of the calorimeter and its contents increased from 25.0 ℃ to 27.7 ℃. a) Write a balanced chemical equation for the reaction that takes place in the bomb calorimeter. b) Calculate the enthalpy of combustion of ethanol per mol. ANSWER a) CH CH OH l O g CO g H O l 3 2 2 2 2 3 2 3 ( ) + → + ( ) ( ) ( ) b) 1 1 . 1.00 46 0.02174 mol 11.0 27.7 25.0 29.7 kJ 29.7 0.0217 ( ) 4 rxn c o o c g Mol of ethanol used gmol q C T kJ C C q H n − − = = = = − = − = − = = − 1366.145 -1 kJ mol
CHAPTER 2 THERMOCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 22 13. In an experiment to measure the enthalpy change of neutralisation, 25.0 mL of 1.0 M HCl is placed in a polystyrene cup, At the same temperature 25.0 mL of 1.0 M NaOH is added and stirred. The temperature of the resulting solution increases by 7.0 ℃. Calculate the enthalpy of neutralisation for this reaction. [Assume the density and specific heat capacity of the final solution are the same as water] ANSWER ( ) ( ) ( ) , 25 25 4.18 7.0 1463 @ 1.463 Heat released q mc T J kJ = = + = 2 HCl NaOH NaCl H O + → + 2 25 1 1000 0.025 1.463 0.025 mol HCl mol NaOH mol H O mol of water mol q Enthalpy of neutralization n kJ mol = = = = = − = = −58.52 -1 kJ mol
CHAPTER 2 THERMOCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 23 14. The combustion of ethanol C2H5OH, occurs according to the following reaction equation: C2H5OH (l) + 3 O2 (g) → 2 CO2 (g) + 3 H2O (g) ΔHo c = ? When a 3.68 g sample of ethanol was burned in excess oxygen in a bomb calorimeter. The temperature rose from 25 ℃ to 66 ℃. a) Define the standard enthalpy of combustion of ethanol. b) If the heat capacity of the calorimeter is 1.98 kJ ℃-1 , calculate ΔHo c? ANSWER a) Standard enthalpy of combustion of ethanol is the heat released when one mol of ethanol @ compound @ substance is combusted @ burned completely @ reacted in excess oxygen at 25℃ and 1 atm @ standard condition. b) ( ) . 3.68 46 0.08 mol 1.98 66 25 81.18 kJ 81.18 0.08 . rxn c c g Mol of ethanol used q C T x q H n = = = = − = − = − = = − 1014 75 -1 kJ mol
CHAPTER 2 THERMOCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 24 MCQ PRACTICES 1. Which of the following is an exothermic process? A ice melting B boiling soup C water evaporating D condensation of water vapour 2. A _____________ ΔH corresponds to an ___________ process. A negative, endothermic B negative, exothermic C zero, endothermic D zero, exothermic 3. The enthalpy of combustion of butane gas (C4H10) is -2878 kJmol-1 . Which statement is incorrect? A Butane releases heat as it burns. B Δ Hf o (C4H10, g) = -2878 kJmol-1 . C Combustion of butane is an exothermic process. D The enthalpy change that accompanies the combustion of 2.500 moles of butane is -7195 kJ. 4. Which statement about enthalpy is true? A heat is given off to the surroundings in endothermic reactions. B some substances have a negative specific heat capacity. C specific heat capacity is the same for all liquids. D the sign of delta H is always negative in exothermic reactions. 5. Consider the following reaction: 2Na2O2 (s) + 2H2O(l) → 4 NaOH (s) + O2 (g) ΔH = -126 kJ The amount of heat released by the reaction of 25.0 g of Na2O2 with water is … A 20.2 kJ B 40.4 kJ C 67.5 kJ D 80.8 kJ 6. An iron nail weighing 4.5 g is cooled from 45 °C to 25 °C. How much is given off in the cooling process? (Given: specific heat of iron = 0.450 Jg-1 °C1 ) A -40.5 kJ B -40.5 J C -405 J D -4.05 kJ 7. A sample of aluminium metal absorbs 9.86 J of heat when its temperature increases from 23.2 °C to 30.5 °C. If the specific heat capacity of aluminium is 0.90 Jg-1 °C-1 , the mass of the sample is … A 1.5 g B 15 g C 8.1 g D 65 g 8. Choose a substance with Δ = 0 A I2 (s) B Na (s) C Br2 (l) D CO2 (g)
CHAPTER 2 THERMOCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 25 9. Which statement is correct for the process H2O (g) → H2O (l)? A ΔH is negative and the process is endothermic. B ΔH is positive and the process is endothermic. C ΔH is negative and the process is exothermic. D ΔH is positive and the process is exothermic. 10. Which of the reactions is the enthalpy of formation? A H g F g HF g 2 2 ( ) + → ( ) 2 ( ) B HCl aq NaOH aq H O l ( ) + + ( ) 2 ( ) C C H l O g CO g H O l 7 16 2 2 ( ) + → + 11 7 8 ( ) ( ) ( ) D I2 (s) → I2 (g) 11. Which of the following reactions is not an equation corresponding to an enthalpy change of formation? A Si (s) + 2H2 (g) → SiH4 (g) B C (s) + 1/2 O2 (g) → CO (g) C Al (s) + 3/2 Br2 (l) → AlBr3 (l) D Fe (s) + S (s) + 2 O2 (g) → FeSO4 (s) 12. The amount of heat required to raise the temperature of one gram of a substance by one degree celsius is called: A heat capacity B heat of combustion C specific heat combustion D specific heat capacity 13. Which of the following processes is exothermic? A K (g) → K+ (g) + eB Br (g) + e- → Br - (g) C 1/2 Br2 (l) → Br (g) D KBr (s) → K+ (g) + Br- (g) 14. Calculate the amount of heat needed to increase the temperature of 2.0 g of iron (Fe) by 2°C. Given the specific heat capacity of iron is 0.44 Jg-1 °C-1 A 0.88 J B 1.76 J C 0.44 J D 0.66 J 15. Given the following data: ( ) ( ) ( ) ( ) ( ) ( ) 2 3 2 2 3 3 395.2 2 2 2 198.2 S s O g SO g kJ SO g O g SO g kJ + → = − + → = − Calculate ΔH for the reaction: S (s) + O2 (g) → SO2 (g) A -296.1 kJ B 226 kJ C -11 kJ D 255.95 kJ 16. In an experiment, 2.4 g of magnesium powder is added to 100 cm3 of 2.0 mol/cm3 copper (II) sulphate solution. The temperature of the mixture increases by 1.0 °C. What is the heat of the reaction in the experiment? [specific heat capacity of solution is 4.2 Jg1 °C-1 ; relative atomic mass of Mg = 24] A -0.42 kJmol-1 B -0.48 kJmol-1 C -4.20 kJmol-1 D -4.80 kJmol-1 17. V cm3 of water is being cooled from 30°C to 4°C inside the refrigerator. 54.6 kJ of heat is released. What is the volume of V? A 0.5 cm3 B 5 cm3 C 50 cm3 D 500 cm3
CHAPTER 2 THERMOCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 26 18. The following thermochemical equation shows a reaction. Based on the equation, which statement is correct? 2 2 CuO H Cu H O H kJ 130.5 + → + = + A The reaction is exothermic. B The activation energy is 130.5 kJmol-1 . C The temperature of the mixture decrease. D The total energy of the reactants is higher than the products. 19. The following chemical equation shows the reaction of the formation of magnesium carbonate. 2 2 1 3 3 Mg CO MgCO H kJmol 25.2 + − − + → = + Heat change Type of reaction A Heat is released Endothermic B Heat is absorbed Exothermic C Heat is released Exothermic D Heat is absorbed Endothermic 20. The following information shows the results of an experiment to study the heat of combustion of butanol, C4H9OH. ➢ Volume of water in the metal container = 250 cm3 ➢ Initial temperature of water = 25.0°C ➢ Highest temperature of water = T °C What is the highest temperature, T °C obtained in this experiment if 1.11 g of butanol is completely burnt? [specific heat capacity of water = 4.2 Jg-1 °C-1 ; relative molecular mass of butanol = 74; heat of combustion of butanol = 2 450 kJmol-1 ] A 60.0 °C B 42.0 °C C 35.0 °C D 30.0 °C
CHAPTER 3 ELECTROCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 27 CHAPTER 3 ELECTROCHEMISTRY
CHAPTER 3 ELECTROCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 28 SUBJECTIVE PRACTICES 1. a) Define i. electrode potential ii. oxidation iii. reduction iv. redox reaction ANSWER i) Electrode potential: The difference in electric potential between an electrode and the electrolyte with which it is in contact. ii) Oxidation: Loss of electrons / gain of oxygen / loss of hydrogen / or increase in oxidation number. iii) Reduction: Gain of electrons / loss of oxygen / or decrease in oxidation number. iv) Redox reaction: Reactions involving simultaneous oxidation and reduction. b) A galvanic cell consists of an Al electrode in 1.0 M Al(NO3)3, a Pb electrode in 1.0 M Pb(NO3)2 and a KCl salt bridge. i. Draw and label the cell diagram. ii. Write the half-cell and overall cell equations. iii. Write the cell notation. iv. State the functions of salt bridge. v. Which electrode will increase in weight? Explain your answer. ANSWER i) ii) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) 3 2 2 3 : 3 : 2 : 2 3 2 3 Anode Al s Al aq e Cathode Pb aq e Pb s Overall equation Al s Pb aq Al aq Pb s + + + + + → + → + → + iii) ( ) ( ) ( ) ( ) 3 2 Al s Al aq M Pb aq M Pb s , 1 , 1 + + iv) Functions of salt bridge: it maintains ionic balance in cell (maintain electrical neutrality). it prevents the electrolytes in two half-cells from mixing. complete the circuit by allowing ions carrying charge to move from one half-cell to the other. v) Cathode (Pb) because Pb2+ ions in the solution undergo reduction to form Pb atoms that deposit on the cathode.
CHAPTER 3 ELECTROCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 29 2. Which species in each pair is a better oxidising agent under standard state conditions? a) Br2 or Au3+ b) H + or Ag+ c) Cd2+ or Cr3+ d) O2 in an acidic medium or O2 in a basic medium ANSWER a) Au3+ b) Ag+ c) Cd2+ d) O2 in acidic medium 3. Which species in each pair is a better reducing agent under standard conditions? a) Na or Li b) H2 or Ic) Fe2+ or Ag d) Bror Co2+ ANSWER a) Li b) H2 c) Fe2+ d) Br − 4. Predict whether Fe3+ can oxidise Ito I2 under standard state conditions. ANSWER ( ) ( ) ( ) ( ) 2 3 2 2 2 0.53 0.77 o o I s e I aq E V Fe aq e Fe aq E V − − + − + + → = + + → = + 3 0.77 0.53 0.24 spontaneous reaction o o o E cell E E cathode anode V V V Fe can oxidise I + − = − = − = +
CHAPTER 3 ELECTROCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 30 5. a) The standard electrode potential for Ag+ |Ag and Pb2+|Pb are 0.799 V and -0.126V respectively. i. Determine the anode and cathode. ii. Calculate the standard cell potential. ANSWER i) of Ag is more positive undergoes reduction Cathode: Ag Anode: Pb o E red Ag + + ii) 0.799 (-0.126 ) 0.925 o o o E cell E E cathode anode V V V = − = − = + b) For the reaction, 24+ () + () → 23+ () + 2+() ˚ = +1.89 the standard reduction potential for Co2+ is -0.28 V. Calculate the standard reduction potential for the change of Ce4+ to Ce3+ . ANSWER ( ) ( ) ( ) ( ) 4 3 2 2 2 1.89 (-0.28 ) 1.61 o o o cathode anode o cathode o cathode Ce aq Co s Ce aq Co aq E cell E E E V E V + + + + → + = − = − = +
CHAPTER 3 ELECTROCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 31 6. Based on the cell notation below, Ag (s) | Ag+ (aq) || M3+ (aq) | M (s) E˚ = +1.00 V a) Write a balance equation for the spontaneous reaction in the cell. b) Name the oxidising agent. c) Calculate ˚3+|. [˚+| = +0.80 ] ANSWER a) ( ) ( ) ( ) ( ) 3 3 3 Ag s M aq Ag aq M s + + + → + b) 3 M + c) 3 3 3 / / / / 1.0 (-0.8 ) 1.8 o o o cathode anode o o M M Ag Ag o M M o M M E cell E E E E V E V E V + + + + = − = − = − = + 7. Predict whether the following reactions would occur spontaneously in aqueous solution at 25˚C. Assume that the initial concentrations of the dissolved species are all 1.0 M. a) Ca (s) + Cd2+ (aq) → Ca2+ (aq) + Cd (s) b) 2Br- (aq) + Sn2+ (aq) → Br2 (l) + Sn (s) c) 2Ag (s) + Ni2+ (aq) → 2Ag+ (aq) + Ni (s) d) Cu+ (aq) + Fe3+ (aq) → Cu2+ (aq) + Fe2+ (aq) ANSWER a) (-0.40 ) (-2.87 ) 2.47 (spontaneous) o o o E cell E E cathode anode V V V = − = − = + b) (-0.14 ) (1.07 ) 1.21 ( spontaneous) o o o E cell E E cathode anode V V V non = − = − = − − c) (-0.25 ) (0.80 ) 1.05 ( spontaneous) o o o E cell E E cathode anode V V V non = − = − = − − d) (0.77 ) (0.15 ) 0.62 (spontaneous) o o o E cell E E cathode anode V V V = − = − = +
CHAPTER 3 ELECTROCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 32 8. A galvanic cell consists of a lead anode immersed in a 1.00 M solution of Pb(NO3)2 and a platinum cathode that has gaseous hydrogen bubbling over it at a pressure of 1.00 atm. The hydrogen ion concentration of the solution is 1.00 M. a) Show the equations for the reactions that occur at anode and cathode. b) Write the cell notation for this reaction. c) Calculate the standard cell potential, E˚ cell. d) Predict the spontaneity of the reaction. [˚2+| = − 0.13 ; ˚+|2 = + 0.00 ] ANSWER a) ( ) ( ) ( ) ( ) ( ) ( ) 2 0 0 2 : 2 0.13 : 2 2 0.00 Anode Oxidation Pb s Pb aq e E V Cathode Reduction H aq e H g E V + + + = − + → + → = b) ( ) ( ) ( ) ( ) ( ) 2 2 Pb s Pb aq M H g atm H aq M Pt s , 1.00 , 1 ,1.00 + + c) (0 ) (-0.13 ) 0.13 o o o E cell E E cathode anode V V V = − = − = + d) Spontaneous reaction 9. The standard electrode potentials are given below: ( ) ( ) ( ) ( ) 2 2 2 0.250 2 0.136 Ni aq e Ni s E V Sn aq e Sn s E V + − + − + → = − + → =− a) Write the equation for the spontaneous reaction. b) Write the cell notation. c) Calculate the E˚ cell ANSWER a) ( ) ( ) ( ) ( ) 2 2 Sn aq Ni s Sn s Ni aq + + + → + b) ( ) ( ) ( ) ( ) 2 2 Ni s Ni aq M Sn aq M Sn s , 1 , 1 + + c) ( 0.136 ) ( 0.250 ) 0.114 o o o E cell E E cathode anode V V V = − = − − − = +
CHAPTER 3 ELECTROCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 33 10. Determine the gaseous products formed at the anode and the cathode in the electrolysis of, a) Molten MgCl2. b) Dilute NaCl solution. c) Concentrated NaCl solution. d) Aqueous Na2SO4 solution. ANSWER a) ( ) ( ) ( ) ( ) 2 2 : 2 2 : 2 Anode Cl l Cl g e chlorine gas Cathode Mg l e Mg s solid magnesium − − + − → + − + → − b) ( ) ( ) ( ) ( ) ( ) 2 2 2 2 : 2 4 4 : 2 2 2 Anode H O l O g H aq e oxygen gas Cathode H O e H g OH aq hydrogen gas + − − − → + + − + → + − c) ( ) ( ) ( ) ( ) – 2 – 2 2 : 2 2 : 2 2 2 Anode Cl aq Cl g e chlorine gas Cathode H O e H g OH aq hydrogen gas − − → + − + → + − d) ( ) ( ) ( ) ( ) ( ) 2 2 – 2 2 : 2 4 4 : 2 2 2 Anode H O l O g H aq e oxygen gas Cathode H O e H g OH aq hydrogen gas + − − → + + − + → + − 11. Consider the electrolysis of molten barium chloride, BaCl2. a) Write the half-reactions of the electrolysis. b) If the molten barium chloride is changed to dilute aqueous solution of barium chloride, write half equation at the anode and cathode. ANSWER a) ( ) ( ) ( ) ( ) 2 2 : 2 2 : 2 Anode Cl l Cl g e Cathode Ba l e Ba s − − + − → + + → b) ( ) ( ) ( ) ( ) ( ) 2 2 2 2 : 2 4 4 : 2 2 2 Anode H O l O g H aq e Cathode H O e H g OH aq + − − − → + + + → +
CHAPTER 3 ELECTROCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 34 MCQ PRACTICES 1. In a galvanic cell A Chemical energy is converted into electricity. B Chemical energy is converted into heat. C Electrical energy is converted into chemical energy. D Electrical energy is converted into heat. 2. The diagram of a standard hydrogen electrode is shown below: Which of the following statements is/are incorrect? I. The pressure of the hydrogen gas is 1.00 kPa. II. The acid solution used is 0.50 mol dm-3 sulphuric acid. III. The temperature of the acid solution is kept constant at 25oC. A I only B I and II only C II and III only D I, II and III 3. A decrease in oxidation number is called: A Oxidation B Reduction C Oxidation-Reduction D All the above represents the same entity. 4. The standard reduction potential for the half-cell reaction Fe3+ + ē → Fe2+ is +0.77V. Which cell would be used to determine this standard value? A Fe electrode in 1 mol dm-3 Fe3+ against Fe electrode in 1 mol dm-3 Fe2+ . B Pt electrode in 1 mol dm-3 Fe3+ against Pt electrode in 1 mol dm-3 Fe2+ . C Fe electrode in 1 mol dm-3 Fe3+ and 1 mol dm-3 Fe2+ against a standard hydrogen electrode. D Pt electrode in 1 mol dm-3 Fe3+ and 1 mol dm-3 Fe2+ against a standard hydrogen electrode. 5. The standard reduction electrode potential for several half-reactions at 298 K are shown below. Electrode reaction E˚ (V) X2 + 2ē → 2X- +0.54 Y 3+ + ē → Y2+ +0.77 Z 2+ + ē → Z -0.25 Which of the following species is the strongest oxidising agent? A X - B Y 3+ C Z D X2 6. The standard reduction potentials of X, Y, Z metals are 0.52, -3.03, -1.18 respectively. The order of reducing power of the corresponding metals is A Y > Z > X B X > Y > Z C Z > Y > X D Z > X > Y
CHAPTER 3 ELECTROCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 35 7. Consider the half-cells below: Hal-cell reaction E˚ / V I Ba2+ + 2ē → Ba -2.9 II Cr 3+ + 3ē → Cr -0.74 III Co 2+ + 2ē → Co -0.28 IV PbO2 + 4H+ + 2ē → Pb2+ + 2H2O +1.17 Which of the following combinations give the highest standard cell potential? A I and II only B II and III only C II and IV D I and IV 8. Without losing its concentration ZnCl2 solution cannot be kept in contact with A Au B Al C Ag D Pb 9. The diagram below shows the arrangement of an electrochemical cell. The standard electrode potentials of some metals are given below: Electrode System E˚ / V Ag+ (aq) | Ag (s) +0.80 Cu2+ (aq) | Cu (s) +0.34 Fe2+ (aq) | Fe (s) -0.44 Zn2+ (aq) | Zn(s) -0.76 Which solution is suitable to be used as Mx+? I. AgNO3 II. CuSO4 III. ZnSO4 A I and II B II and III C I and III D I, II and III 10. The composition of a standard hydrogen electrode is: A Hydrogen gas B H + ions C Platinum electrode D All the above 11. Which of the following is NOT a characteristic feature of a salt bridge? A It does not maintain electrical neutrality of the electrolytic solutions of the halfcells. B Salt bridge joins the two halves of an electrochemical cell. C It completes the inner circuit. D It is filled with a salt solution. 12. Which of the following solution(s) will produce hydrogen gas when electrolyzed using platinum electrode? I. Water II. Dilute sodium hydroxide III. Dilute hydrochloric acid A I and II B II and III C I and III D I, II and III 13. What is the direction of flow of electrons in an electrolytic cell? A Anode to cathode externally. B Anode to cathode internally. C Cathode to anode externally. D Cathode to anode in the solution.
CHAPTER 3 ELECTROCHEMISTRY Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 36 14. The following factors on the selective discharge of a species at the electrodes are true except: A Concentration of the species. B Nature of electrodes. C Size of electrodes. D Standard Reduction Potential (SRP) of the species. 15. If electricity is passed through a CuSO4 solution by using a Pt electrode, then which of the following possible change occurs? A H2 is deposited at the cathode. B Colour of the solution becomes fade. C Cu is deposited at the anode. D All are possible. 16. The technique that uses electricity to break apart molecules is called: A Electrolysis. B Hydrolysis. C Electron reduction. D Photosynthesis. 17. Positive ions (cation) move towards the cathode (-) where they discharge by A Breaking apart. B Clamping together. C Losing electrons. D Gaining electrons. 18. What is the name given to the solution that is being electrolysed? A Electrolyte. B Salt solution. C Mineral solution. D Electric solution. 19. Explain why the electrolyte must be an aqueous/ molten/ liquid? A So that the ions can move. B So that it doesn’t get too hot. C So that the electron can move. D So that the ions will remain at electrode. 20. Which one of the following reactions will NOT occur spontaneously? A ( ) ( ) ( ) ( ) 2 Mg s Ag aq Mg aq Ag s 2 2 + + + + → B ( ) ( ) ( ) ( ) 2 2 Cu aq Zn s Cu s Zn aq + + + + → C ( ) ( ) ( ) ( ) 2 2 Hg aq Zn s Hg l Zn aq + + + + → D ( ) ( ) ( ) ( ) 2 2 2 Ag s Ni aq Ag aq Ni s + + + + →
CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 37 CHAPTER 4 INTRO TO ORGANIC CHEMISTRY
CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 38 SUBJECTIVE PRACTICES 1. Gives structures of all organic compounds below and identify the elements that made up the organic compounds. a) Methane b) Glucose c) Urea d) DDT e) Penicilin f) Nicotine g) Caffeine h) Glutamic acid ANSWER a) Structure: Elements: Methane (CH4) Carbon, Hydrogen b) Structure: Elements: Glucose (C6H12O6) Carbon, Hydrogen, Oxygen c) Structure: Elements: Urea (CO(NH2)2) Carbon, Hydrogen, Nitrogen, Oxygen d) Structure: Elements: DDT (C14H9Cl5) Carbon, Hydrogen, Chlorine e) Structure: Elements: Penicillin (C16H18N2O5S) Carbon, Hydrogen, Nitrogen, Sulphur, Oxygen f) Structure: Elements: Nicotine (C10H14N2) Carbon, Hydrogen, Nitrogen g) Structure: Elements: Caffeine (C8H10N4O2) Hydrogen, Nitrogen, Oxygen h) Structure: Elements: Glutamic acid (C5H9NO4) Carbon, Hydrogen, Nitrogen, Oxygen
CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 39 2. Complete the following table by drawing the structural formula of C3H7Cl based on the following description. Structural formulae Description Structural formula of C3H7Cl Expanded structure Show all atoms and bonds: bonds are drawn as lines Condensed structure Bonds are not always shown; subscripts are used to indicate the number of identical groups attached to a particular atom. Skeletal structure Shows the carbon skeleton and functional groups ANSWER Structural formulae Description Structural formula of C3H7Cl Expanded structure Show all atoms and bonds: bonds are drawn as lines Condensed structure Bonds are not always shown; subscripts are used to indicate the number of identical groups attached to a particular atom. Skeletal structure Shows the carbon skeleton and functional groups
CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 40 3. Draw the expanded, skeletal or condensed structure for the followings: Expanded Structure Condensed Structure Skeletal Structure CH CH CH NH 3 2 2 2 CH CH CH(Br)CH COOH 3 2 2
CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 41 ANSWER Expanded Structure Condensed Structure Skeletal Structure CH CH(CH )OH 3 3 CH CH CH COCH 3 2 2 3 CH CH CH NH 3 2 2 2 CH CH CH(Br)CH COOH 3 2 2 O=CHCH CH=CHCH 2 3 CH CHClCH COOCH 3 2 3
CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 42 4. Draw the expanded structure for each compound given below and classify each carbon and hydrogen atoms (where appropriate) as primary, secondary, tertiary or quaternary. a) b) 3 3 2 (CH ) CCH OH ANSWER: ANSWER: 5. Circle and name all the functional groups present in the following compounds below. a) b) c) d) e) f) g) h) i) j) k)
CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 43 ANSWER a) b) c) d) e) f) g) h) i) j) k) Carbon – carbon double bond carboalkoxy Carbon – carbon double bond
CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 44 6. Name the functional group present in the following compounds and classify the compounds according to their homologous series: a) CH3COCl b) CH3COOCOCH3 c) CH2=CH2 ANSWER a) CH3COCl - functional group = acyl | homologous series = acyl chloride b) CH3COOCOCH3 - functional group = anhydride | homologous series = anhydride c) CH2=CH2 - functional group = Carbon-Carbon double bond | homologous series = alkenes 7. Determine which of the following compounds are saturated and unsaturated hydrocarbons. a) b) c) d) e) f) g) h) i) j) ANSWER Saturated hydrocarbons= Structure A, G, I & J Unsaturated hydrocarbons= Structure B, C, D, E, F & H
CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 45 8. Complete the table below by drawing the isomer of given molecule based on the following description. Isomer Description Isomer of Chain isomer ➢ Differ in the carbon skeleton (different in the longest carbon chain). ➢ Possess same functional group and belong to the same homologous series. ➢ Have same chemical properties but different physical properties Positional isomer ➢ These isomers have a substituent group in different positions in the same carbon skeleton. Functional group isomer ➢ Have same general formula. ➢ Have different functional groups and belong to different homologous series with the same general formula. ➢ Different classes of compounds that exhibit functional group isomerism. ANSWER Isomer Description Isomer of Chain isomer ➢ Differ in the carbon skeleton (different in the longest carbon chain). ➢ Possess same functional group and belong to the same homologous series. ➢ Have same chemical properties but different physical properties Positional isomer ➢ These isomers have a substituent group in different positions in the same carbon skeleton. Functional group isomer ➢ Have same general formula. ➢ Have different functional groups and belong to different homologous series with the same general formula. ➢ Different classes of compounds that exhibit functional group isomerism.
CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 46 9. Draw all possible structure of isomers. Identify the types of isomerism present by give the pairs of isomers (if any) of the following compounds. a) CH2=CHCH2CH3 b) CH3CH2CH2CH2CH2OH ANSWER a) Chain isomers Positional isomers Functional group isomers b) Chain isomers Positional isomers Functional group isomers 10. A volatile, sweet-smelling organic compound X contains carbon, hydrogen, and oxygen. Its empirical formula is C4H8O2. a) Draw the structural formula of X. b) Draw 1 possible isomers of X with same functional group. c) Draw another isomer of X with different functional group. ANSWER a) b) c)
CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 47 11. a) State 3 differences between a homolytic and a heterolytic cleavage. b) Draw the products of homolytic or heterolytic of each indicated bond. i) Homolytic of: ii) Heterolytic of: Classify each carbon reactive intermediate as a carbon free radical or carbocation. ANSWER a) HOMOLYTIC CLEAVAGE HETEROLYTIC CLEAVAGE Covalent bond divided equally between 2 atoms. Covalent bond divided unequally between 2 atoms. Involving two atoms of same electronegativity. Involving two atoms of different electronegativity. Formed free radicals. Formed cation and anion. b) Homolytic of: Reactive intermediate: Carbon free radical Heterolytic of: Reactive intermediate: Carbocation
CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 48 12. Arrange the following carbocations in the increasing order of stability. Explain. a) I II III IV b) I II III ANSWER a) III < I < IV < II Carbocation is electron deficient. Carbocation stabilized by substituent such as the alkyl group which is electron releasing group. If number of alkyl group increase, the more stable the carbocation. Structure II most stable carbocation because have 3 alkyl groups attached to the carbocation. While structure III least stable because only hydrogen atom attached to the carbocation. b) III < I < II Carbocation is electron deficient. Carbocation stabilized by substituent such as the alkyl group which is electron releasing group. If number of alkyl group increase, the more stable the carbocation. Structure III has no alkyl group, thus it’s the less stable carbocation. Meanwhile structure I & II has 2 alkyl group and 3 alkyl group respectively. Structure II most stable because has 3 alkyl group attached to carbocation. 13. Arrange the following carbon free radicals in the decreasing order of stability. a) I II III IV b) I II III IV ANSWER a) III > IV > I > II b) I > IV > III > II
CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 49 14. State the type of each of the following chemical reactions. a) Cl2 , FeCl3 Cl + HCl b) + HBr Br c) d) H3 C C O Cl excess NH3 H C3 C O NH2 e) f) H C2 CH2 + HCl H C3 CH2 Cl g) H C3 CH Br CH3 KOH, CH3 CH2OH reflux H C3 CH CH2+ HBr h) CH4 Br2 uv CH3Br + HBr i) conc. HNO3 , conc. H2 SO4 NO2 j) OH conc. H2 SO4 + H2O ANSWER a) Substitution b) Addition
CHAPTER 4 INTRO TO ORGANIC CHEM Lecturer’s Edition DK024 Chemistry 2 Labuan Matriculation College 50 c) Addition d) Substitution e) Substitution f) Addition g) Elimination h) Substitution i) Substitution j) Elimination 15. a) Based on compound CH3CH(OH)COOH. i. Draw its skeletal and expanded structures. ii. Name all functional groups and homologous series present. b) Structural isomerism can be classified into a chain, positional and functional group isomerism. i. Define structural isomerism. ii. Compound A is a cyclic compound having the molecular formula of C5H10. Draw all possible structural isomer for compound A that have cyclic structures. c) Given the carbocations below: i. State the class of each carbocation. ii. Arrange the carbocations in order of increasing stability. d) Name the type of reaction for each of the following conversions. a) - - CH CH Cl + OH CH CH OH + Cl 3 2 3 2 → b) H H C H H C Cl H C H H KOH, Ethanol reflux H H C H C H C H H + HCl c) O H C C C H H H H H NaCN, HCl CN OH H C C C H H H H H e) State the number of 1o , 2o and 3o carbon(s) and hydrogens in the compound below.