7. Question 7 [10 marks total] At 20 C, a cube of zinc (Zn) has an edge length of 10 cm. The mass of the cube is 7.14 kg. L = 10 cm a. Calculate the density of zinc at 20 .C. [2] The temperature of the block is changed to Tr. The percentage change in density, %Ap, is - 4.1%. The linear coefficient of thermal expansion of zinc, azinc = 40 x 10-6 .C-1 b. Calculate the density of the zinc at Tf. [2] c. Calculate the edge length of the zinc cube at T. Give your answer in cm to 4 decimal places.[2] d. Calculate the value of Ti. [4] PAGE 8 OF 119. Question 9 [10 marks total] Consider the stress-strain graph shown below for material A and material B: 1000 800 600 Stress (MPa) 400 B 200 0.01 0.02 0.03 0.04 0.05 0.12 Strain a. Calculate the Young's modulus for each material. b. Which material has a higher stiffness? Explain your reasoning. [2] c. Which material is more brittle? Explain your reasoning. [2] d. Estimate the toughness of Material B. [2] PAGE 10 OF 111. Question 1 [10 marks total] A gas sample is made of a mixture of two ideal gases. The sample has a total pressure of 1.0 x 105 Pa and a voiume of 0.040 m3 at a temperature of 80 \"C. a) Calculate the total number of moles of gas in the sample. [2] The gas mixture contains two gases: carbon dioxide (C02) and neon (Ne). The mole fraction of Ne in the mixture is 0.34 (xNa = 0.34). b) For the conditions given in part (a). calculate the density of the gas. Give your answer in gim3. [5] The temperature of the sample is increased to 150 C. The volume and number of moles of gas remain constant. c) Calculate the new pressure of the gas sample. [2] d) State whether the density will increase, decrease, or remain the same. Explain your reasoning. [1] PAGE 2 OF 11 5. Question 5 [10 marks total] When a material changes phase, heat is either absorbed or released. a) The enthalpy of vaporization (AHvap) is the heat associated with vaporization (liquid ) gas). Is AHvap positive, negative, or equal to zero? Explain your reasoning. [2] A 20 9 sample of an unknown material is initially at a temperature of 10 C and solid. The sample absorbs 15700 J of heat and reaches a final temperature of 100 00, where it is a gas. Some useful constants are included in the table below. Constant Value Units Specific heat capacity of the solid, Csalid 1.60 J g\" "0'1 Specic heat capacity of the liquid, Cliquid 2.20 J g" "(3'1 Specific heat capacity of the gas. Cgas 1.10 J g'1 "C'1 Melting point. Tm 10 C Boiling point, TI, 85 C Molar mass, M 80 9 mar1 Heat of fusion, rtHruS 10.2 kJ mol'1 b) Using the data in the table above, calculate the number of moles in the sample. [1] c) Using the data in the table above, calculate AHvap for the unknown material. Give your answer in kJ mol". PAGE 6 OF 11 [7] . Question 3 [10 marks total] a. Calculate the change in internal energy of the system for the following processes: [2] i) 20 J of heat is released by the system. and 40 J of work is done on the system. ii) 460 J of heat is absorbed by the system. and the system does 50 J of work. A 4.8 mol sample of an ideal gas expands from an initial state (P = 4 x 105 Pa, V = 0.02 m3) to a nal state (P = 'l x 105 Pa, V = 0.08 m3). The initial and final state are shown on the pressure-volume diagram below. 400 Pressure (kPa) _\\ O O 0.02 0.08 Volume (ms) The gas can expand by: a Path 1: two step expansion. (Grey line) . Path 2: isothermal expansion at T = 200 K. (Red line) b. Calculate the work done by the gas on path 1. [3] c. Calculate the work done by the gas on path 2. [3] d. Determine the value of Q for path 2 and state whether heat is absorbed or released. [2] PAGE 4 OF 11