1 1. TABLE 1 shows the standard electrode potentials for various metals. TABLE 1 Metal ion|Metal ... more 1 1. TABLE 1 shows the standard electrode potentials for various metals. TABLE 1 Metal ion|Metal B + |B C 2+ |C D 2+ |D E 2+ |E F 3+ |F E o (V) +0.80-0.28 +0.34-0.76 +1.42 i. Arrange the strength of the above metal ions as reducing agent in ascending order. ii. Referring to the cell notation below, write the redox equation for the cell reaction. C(s) | C 2+ (aq) || D 2+ (aq) | D(s) iii. Calculate E cell at 25 o C, if the concentrations of C 2+ and D 2+ are 0.01 M and 0.10 M respectively. [5 marks] 2. a) Explain the term standard reduction potential of hydrogen electrode and standard reduction potential of electrode. [4 marks] b) Draw a labeled diagram to show how the potential of a galvanic cell derived from the following two half reactions can be measured. Cu 2+ (aq) + 2e Cu(s) Ag + (aq) + e Ag(s) E o = 0.34 V E o = 0.80 V Explain the chemical reactions taking place in the cell. [7 marks] c) Compare and contrast between an electrolytic cell and a galvanic cell. [4 marks] 3. a) When 0.60 A of an electrical current is passed for 11.7 minutes, all the permanganate ions in 15.0 mL solution have been reduced. Determine the original concentration of permanganate ions. Given: MnO 4-+ 8H + + 5e- Mn 2+ + 4H 2 O [5 marks] b) The cell potential for the galvanic cell below is 2.299 V at 25 o C. Zn(s) | Zn 2+ (0.040 M) || Cl 2 (g, 1 atm) | Cl-(0.005 M) | Pt(s) Write the half-reactions of the anode and cathode, and the overall reaction. Calculate the standard electrode potential, E o for the Cl 2 | Cl-electrode. Determine the equilibrium constant of the reaction. (E o Zn Zn | 2 =-0.763 V) [10 marks]
Determine the enthalpy change, ΔH f for the reaction C(graphite) + 2H 2 (g) CH 4 (g) Given: C(g... more Determine the enthalpy change, ΔH f for the reaction C(graphite) + 2H 2 (g) CH 4 (g) Given: C(graphite) + O 2 (g) CO 2 (g) ΔH 1 =-393.5 kJ 2H 2 (g) + O 2 (g) 2H 2 O(l) ΔH 2 =-571.6 kJ CH 4 (g) + 2O 2 (g) 2H 2 O(l) + CO 2 (g) ΔH 3 =-890.4 kJ [3 marks] 2. Draw the Born-Haber cycle for the formation of magnesium chloride, MgCl 2 from magnesium metal and chlorine gas. Calculate the enthalpy of formation of MgCl 2. Given: Heat of sublimation of magnesium, ΔH 1 = 149 kJ mol-1 First ionization energy of magnesium, ΔH 2 = 740 kJ mol-1 Second ionization energy of magnesium, ΔH 3 = 1456 kJ mol-1 Heat of atomization of chlorine, ΔH 4 = 240 kJ mol-1 Electron affinity of chlorine, ΔH 5 =-369 kJ mol-1 Lattice energy of MgCl 2 , ΔH 6 =-3933 kJ mol-1 [10 marks] 3. FIGURE 1 shows an energy cycle for the dissolution of halogen, X 2. X represents bromine or iodine.
1 | A d d i t i o n a l Q u e s t i o n s C h a p t e r 9 T h e r m o c h e m i s t r y S K 0 2 6... more 1 | A d d i t i o n a l Q u e s t i o n s C h a p t e r 9 T h e r m o c h e m i s t r y S K 0 2 6 1 a) i. Define standard enthalpy of formation, H° f. ii. Calculate the standard enthalpy of formation of ethanol if, ∆Hºc [C (s)] = 393 kJ mol 1 ∆Hºc [H 2 (g)] = 293 kJ mol 1 ∆Hºc [C 2 H 5 OH (l)] = 1376 kJ mol 1 [5 marks] b) Construct a Born-Haber cycle for magnesium chloride compound and determine the second ionization energy of magnesium by using the data given below: Enthalpy of sublimation = +149 kJ mol 1 First ionization energy of magnesium = +740 kJ mol 1 Enthalpy of atomization of chlorine = +121 kJ mol 1 Electron affinity of chlorine = 364 kJ mol 1 Lattice energy of magnesium chloride = 2773 kJ mol 1 Enthalpy of formation of magnesium chloride = 870 kJ mol 1 [5 marks] 2 a) Define the enthalpy of combustion. [1 mark] b) In a calorimetry study, powdered xylose, C 5 H 10 O 5 combusted in a bomb calorimeter. The following data was obtained: mass of xylose burned = 1.183 g heat capacity of calorimeter = 4.728 kJ C 1 initial calorimeter temperature = 23.29 C final calorimeter temperature = 27.19 C i. Calculate the heat of combustion of xylose in kilojoule per mole. ii. Write the thermochemical equation for the combustion of xylose. [7 marks] c) Which substance in the following pair has a larger lattice energy? Explain. KCl or RbCl [2 marks] 3 a) A 0.1375 g of magnesium is burned in a constant volume bomb calorimeter that has a heat capacity of 1769 J C 1. If the calorimeter contains 300 g of water and the temperature increases by 1.126C, calculate the heat of combustion of magnesium in kJ mol 1. [5 marks] b) Based on the data given below: ∆H hydration Na + = 390 kJ mol 1 ∆H hydration Cl = 380 kJ mol 1 ∆H solution NaCl = +6 kJ mol 1 i. Construct an energy cycle diagram to show the dissolution of solid NaCl. ii. Calculate the lattice energy of NaCl. [5 marks]
Energy Reaction coordinate M Q R P N 1 a) The reaction, 2ClO 2 (aq) + 2OH (aq) ClO 3 (aq) + C... more Energy Reaction coordinate M Q R P N 1 a) The reaction, 2ClO 2 (aq) + 2OH (aq) ClO 3 (aq) + ClO 2 (aq) + H 2 O (l) was studied and the following results were obtained. Experiment [ClO 2 ], M [OH ], M Rate, Ms 1 1 0.060 0.030 0.02480 2 0.020 0.030 0.00276 3 0.020 0.090 0.00828 i. Determine the rate law for the reaction. ii. Calculate the rate constant. iii. Calculate the reaction rate when [ClO 2 ] = 0.010 M and [OH ] = 0.015 M. [9 marks] b) i. Of the curves, M and N, one represents the uncatalysed reaction and the other reaction is in the presence of a catalyst. Which is which? ii. What are the quantities marked P, Q and R. iii. How does a catalyst work? [6 marks]
1 1. TABLE 1 shows the standard electrode potentials for various metals. TABLE 1 Metal ion|Metal ... more 1 1. TABLE 1 shows the standard electrode potentials for various metals. TABLE 1 Metal ion|Metal B + |B C 2+ |C D 2+ |D E 2+ |E F 3+ |F E o (V) +0.80-0.28 +0.34-0.76 +1.42 i. Arrange the strength of the above metal ions as reducing agent in ascending order. ii. Referring to the cell notation below, write the redox equation for the cell reaction. C(s) | C 2+ (aq) || D 2+ (aq) | D(s) iii. Calculate E cell at 25 o C, if the concentrations of C 2+ and D 2+ are 0.01 M and 0.10 M respectively. [5 marks] 2. a) Explain the term standard reduction potential of hydrogen electrode and standard reduction potential of electrode. [4 marks] b) Draw a labeled diagram to show how the potential of a galvanic cell derived from the following two half reactions can be measured. Cu 2+ (aq) + 2e Cu(s) Ag + (aq) + e Ag(s) E o = 0.34 V E o = 0.80 V Explain the chemical reactions taking place in the cell. [7 marks] c) Compare and contrast between an electrolytic cell and a galvanic cell. [4 marks] 3. a) When 0.60 A of an electrical current is passed for 11.7 minutes, all the permanganate ions in 15.0 mL solution have been reduced. Determine the original concentration of permanganate ions. Given: MnO 4-+ 8H + + 5e- Mn 2+ + 4H 2 O [5 marks] b) The cell potential for the galvanic cell below is 2.299 V at 25 o C. Zn(s) | Zn 2+ (0.040 M) || Cl 2 (g, 1 atm) | Cl-(0.005 M) | Pt(s) Write the half-reactions of the anode and cathode, and the overall reaction. Calculate the standard electrode potential, E o for the Cl 2 | Cl-electrode. Determine the equilibrium constant of the reaction. (E o Zn Zn | 2 =-0.763 V) [10 marks]
Determine the enthalpy change, ΔH f for the reaction C(graphite) + 2H 2 (g) CH 4 (g) Given: C(g... more Determine the enthalpy change, ΔH f for the reaction C(graphite) + 2H 2 (g) CH 4 (g) Given: C(graphite) + O 2 (g) CO 2 (g) ΔH 1 =-393.5 kJ 2H 2 (g) + O 2 (g) 2H 2 O(l) ΔH 2 =-571.6 kJ CH 4 (g) + 2O 2 (g) 2H 2 O(l) + CO 2 (g) ΔH 3 =-890.4 kJ [3 marks] 2. Draw the Born-Haber cycle for the formation of magnesium chloride, MgCl 2 from magnesium metal and chlorine gas. Calculate the enthalpy of formation of MgCl 2. Given: Heat of sublimation of magnesium, ΔH 1 = 149 kJ mol-1 First ionization energy of magnesium, ΔH 2 = 740 kJ mol-1 Second ionization energy of magnesium, ΔH 3 = 1456 kJ mol-1 Heat of atomization of chlorine, ΔH 4 = 240 kJ mol-1 Electron affinity of chlorine, ΔH 5 =-369 kJ mol-1 Lattice energy of MgCl 2 , ΔH 6 =-3933 kJ mol-1 [10 marks] 3. FIGURE 1 shows an energy cycle for the dissolution of halogen, X 2. X represents bromine or iodine.
1 | A d d i t i o n a l Q u e s t i o n s C h a p t e r 9 T h e r m o c h e m i s t r y S K 0 2 6... more 1 | A d d i t i o n a l Q u e s t i o n s C h a p t e r 9 T h e r m o c h e m i s t r y S K 0 2 6 1 a) i. Define standard enthalpy of formation, H° f. ii. Calculate the standard enthalpy of formation of ethanol if, ∆Hºc [C (s)] = 393 kJ mol 1 ∆Hºc [H 2 (g)] = 293 kJ mol 1 ∆Hºc [C 2 H 5 OH (l)] = 1376 kJ mol 1 [5 marks] b) Construct a Born-Haber cycle for magnesium chloride compound and determine the second ionization energy of magnesium by using the data given below: Enthalpy of sublimation = +149 kJ mol 1 First ionization energy of magnesium = +740 kJ mol 1 Enthalpy of atomization of chlorine = +121 kJ mol 1 Electron affinity of chlorine = 364 kJ mol 1 Lattice energy of magnesium chloride = 2773 kJ mol 1 Enthalpy of formation of magnesium chloride = 870 kJ mol 1 [5 marks] 2 a) Define the enthalpy of combustion. [1 mark] b) In a calorimetry study, powdered xylose, C 5 H 10 O 5 combusted in a bomb calorimeter. The following data was obtained: mass of xylose burned = 1.183 g heat capacity of calorimeter = 4.728 kJ C 1 initial calorimeter temperature = 23.29 C final calorimeter temperature = 27.19 C i. Calculate the heat of combustion of xylose in kilojoule per mole. ii. Write the thermochemical equation for the combustion of xylose. [7 marks] c) Which substance in the following pair has a larger lattice energy? Explain. KCl or RbCl [2 marks] 3 a) A 0.1375 g of magnesium is burned in a constant volume bomb calorimeter that has a heat capacity of 1769 J C 1. If the calorimeter contains 300 g of water and the temperature increases by 1.126C, calculate the heat of combustion of magnesium in kJ mol 1. [5 marks] b) Based on the data given below: ∆H hydration Na + = 390 kJ mol 1 ∆H hydration Cl = 380 kJ mol 1 ∆H solution NaCl = +6 kJ mol 1 i. Construct an energy cycle diagram to show the dissolution of solid NaCl. ii. Calculate the lattice energy of NaCl. [5 marks]
Energy Reaction coordinate M Q R P N 1 a) The reaction, 2ClO 2 (aq) + 2OH (aq) ClO 3 (aq) + C... more Energy Reaction coordinate M Q R P N 1 a) The reaction, 2ClO 2 (aq) + 2OH (aq) ClO 3 (aq) + ClO 2 (aq) + H 2 O (l) was studied and the following results were obtained. Experiment [ClO 2 ], M [OH ], M Rate, Ms 1 1 0.060 0.030 0.02480 2 0.020 0.030 0.00276 3 0.020 0.090 0.00828 i. Determine the rate law for the reaction. ii. Calculate the rate constant. iii. Calculate the reaction rate when [ClO 2 ] = 0.010 M and [OH ] = 0.015 M. [9 marks] b) i. Of the curves, M and N, one represents the uncatalysed reaction and the other reaction is in the presence of a catalyst. Which is which? ii. What are the quantities marked P, Q and R. iii. How does a catalyst work? [6 marks]
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