Question

Chapter 5 and Chapter 10 Problem solving (please practice the following questions and make sure that you understand the principles behind: you can find Ar from textbook or website I. A 145 g sample of copper metal at 100.0°C is placed into 250.0 g of water at 25.0°C in a calorimeter. When the system reaches thermal equilibrium, the temperature of the water in the calorimeter is 28.8°C. Assume the calorimeter is perfectly insulated. What is the specific heat capacity of copper? 12.45.0 g of ice at -10.0 "Cis mixed with 325 g of water at 37.0 °C. Calculate the final temperature of the nixture. Assume that no energy in the form of heat is transferred to the environment. (Heat of fusion - 333 J/g; specific heat capacities: ice = 2.06 J/g.K, liquid water = 4.18 J/g.K) 3. The thermochemical equation for the combustion of butane is shown below. CHI(g) + 13/2 O2(g) 4 CO2(g) + 5 H2O(1) AH -2877 kJ/mol-rxn What is the enthalpy change for the following reaction? 8 CO(g) + 10 H2O(1) 2 C.H.(g) + 13 O2(g) 4. Iron oxide reacts with aluminum in an exothermic reaction. Fe2O3(s) + 2 Al(s) 2 Fe(s) + Al2O3(s) The reaction of 5.00 g Fe,O, with excess Al(s) evolves 26.6 kJ of energy in the form of heat. Calculate the enthalpy change per mole of Fe2O, reacted. 5 Determine the standard enthalpy of formation of Fe.O.(8) given the thermochemical equations below. 2Fe(s) + 3/2 O (8) ► Fe2O3(s) A F°(Fe,Os) = ? Fe(s) + 3 H2O(1) ► Fe(OH)>(s) + 3/2 H2(g) A Hº +160.9 kJ/mol-rxn H2(g) + 1/2 O2(g) → H2O(l) A.H° = -285.8 kJ/mol-rxn Fe2O,(s) + 3 H2O(1) ► Fe(OH)3(s) AH = +288.6 kJ/mol-rxn 6. The standard enthalpy change for the combustion reaction of 1 mole of ethanol is -1058 kJ. C2H5OH (g) + 3 O2(g) → 2 CO2(g) + 3 H2O(g) Calculate 4/1° for ethanol based on the All of CO2 (g) and H20 (g). 7. A balloon at 0.98 atm contains 0.16 mol of CH4, 0.23 mol of N2, 0.012 mol of He and 0.018 mol of H2. What are the partial pressure of each gas? 8. A gas in a 2.00 L of ballon weigh 7.14 g at 2.00 atm and 27.0°C. What is the molar mass of the gas? 9. Sulfuric acid (H2SO4), the industrial chemical produced in greatest quantity (almost 45 million tons per year in the United States alone), is prepared by the following chemical reaction in the presence of a catalyst. 2S(s) + 302(g) + 2H2O(l) - 2H2SO4(aq) What volume of Oz (in liters) at 22°C and 0.95 atm is required to produce 454 g of H:SO?

Answer 1

1. qcu m *C AT = 145 g* C * (28.8 - 100.0) °C = -10324 * C qwater m *C AT = 250.0 g * 4.184 * (28.8- 25.0) °C 3974.8 At thermal equilibrium, qcu+qwater 0 -10324 C 3974.8 0 10324 C 3974.8 C 0.385006 J/(g.°C) Specific heat capacity of copper 0.385 J/(g.°C)

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2.

Total Mass of ice = 45 g Let T,be the final temperature of water after addition of ice. By the conversion of ice to water at Tf, the following processes will be taken place 1. Ice at 0 °C to water at 0 °C 2. Water at 0 °C to water at T Step- Energy associated with ice at -10.0 °C to ice at 0°C xAT 45 gx2.06 J.g1'C-x(0-(-10)) C 927 J q mxCwater X Energy associated with Ice at 0 °C to water at 0 °C =45 gx333 J.g =1.0 molx 6020 J.mol"1 =14985 J q2=mxAH Energy associated with water at 0 °C to water at T xAT 45 gx4.18 J.g1Cx(T,-0) 'C =188.17, 9 — тxC. water Energy associated with the conversion of ice at 0 °C to water at T is 2q3 =927+14985+188.1 T, =15912 188.1 T, ice Step 2 Mass of water at 37.0 °C is 325 g Energy associated with water of 325 g at 37.0 °C to water at T, is Ямаеr — тxСуаer, х ДТ %3 325 gx4.18 J.mol1:C1x (T, -37.0) "С %31358.51, —50264.5 Step -3 At themal equilibrium ice+ter 0 15912 188.1 T, +1358.5T, - 50264.5 0 1546.6xT, 34352.5 = T 22.21 °C The final temperature of the water after addition of ice = 22.2 °C

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4. Number of moles of Fe203 = mass/mol.wt. 5.00 g/(159.69 g/mol) 0.031311 mol Heat energy released -26.6 kJ Enthalpy change= - 26.6 kJ/ 0.031311 mol = -849.5508 kJ/mol Enthalpy change -849.55 kJ/mol