CHE132S2006Ex01

CHE132S2006Ex01 - CHE132 Midterm 1 Form 0 CHE132 Midterm 1...

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CHE132 Midterm 1 Form 0 1 CHE132 Midterm 1 Spring 2006 Form 0 There are 20 multiple choice questions. Each question is worth 5 points. The entire exam is worth 100 points. Constants The Gas constant = R = 8.314 J mol -1 K -1 = 0.08206 L atm mol -1 K -1 The molar heat capacity of water is 75.291 J mol -1 K -1 . The specific heat capacity of water is 4.184 J g -1 °C -1 The molar mass of water is 18.02 g mol -1 The density of liquid water is 1 g/mL. 1 atm = 1.013 x 10 5 Pa. 1 cm 3 = 1 x10 -3 L = 1 x 10 -6 m 3 1 cal = 4.184 J Equations E sys = q sys + w sys H = q p w sys = -P ext V q = nC T reaction = coeff p f (products) - coeff r f (reactants) S = q T /T G° = H° - T G reaction,T reaction,298K - T reaction,298K S (P 1 atm) = S - RlnP S (c 1 M) = S - Rlnc G reaction = reaction + RTlnQ
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CHE132 Midterm 1 Form 0 2 Question 1. A 20 g piece of iron with T = 300 °C is placed in 250 mL of water in a glass beaker with T = 30 °C. What is the final temperature of the water and iron at thermal equilibrium assuming that q water = -q iron ? The specific heat capacity of iron is 0.451 J g -1 °C -1 . A: 270°C B: 330°C C: 32.31°C D: 27.65°C E: 165°C -m iron c iron (T final – 300) = m water c water (T final – 30) -20x0.451(T final – 300) = 250x4.184(T final – 30) -9.02T final + 2706 = 1046T final – 31380 34086 = 1055.02T final so T final = 32.31 °C Question 2. A 40g sample of water cools from 50 C to 30 C. During this process, 7,420 J of heat are transferred from the water to the surroundings. Calculate the change in energy per mole of the water ( E water ) given that the volume of water is constant during this process. A: -7.5 kJ/mol B: -3.34 kJ/mol C: -1.51 kJ/mol D: The answer cannot be calculated since we do not know the expansion work done by the water. E: 3.36 kJ/mol q water = -7420 J, Moles of water = 2.22. V = 0, so E water = q water / 2.22 = - 3.34 kJ/mol Question 3 Which one of the following statements is not correct: A: A phase change can be exothermic or endothermic. B: The enthalpy change for a chemical reaction ( H) is equal to the heat transferred at constant pressure (q p ). C: Exothermic reactions are always spontaneous. D: If the volume of an ideal gas at constant temperature increases by a factor of 2 then the pressure of the gas will decrease by a factor of 2. E: The combustion of octane is an exothermic reaction. Question 4 Which one of the following statements is not correct: A: In an open system, both matter and energy can be transferred from the system to the surroundings. B: In a closed system, energy but not matter can be transferred from the system to the
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CHE132S2006Ex01 - CHE132 Midterm 1 Form 0 CHE132 Midterm 1...

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