CHEM 1220 - Practice Exam 1v1 - Exam

Question 1 A reaction with activation energy of 123 kJ/mol has a rate constant of 0.200 s at 38 o C. At what temperature will the rate constant be 0.400 s -1 ? 31 o C 43 o C 76 o C 225 o C 349 o C I am unsure and need to study this concept to prepare for the exam Question 2 The rate constant of a second-order reaction is 3.86 x 10 -2 M -1 s -1 . If the concentration of reactant A is 0.160 M after 75.6 sec, what was the initial concentration, [A] 0 ? (Assume the reaction is A → B + C) 0.300 M 0.325 M 1.50 M 2.96 M 3.08 M I am unsure and need to study this concept to prepare for the exam Question 3 A nonelectrolyte has the empirical formula C 3 H 9 Al. A solution of 0.144 g of the compound in 10.0 g of benzene (C 6 H 6 ) boils at 80.35 o C. The normal boiling point of benzene is 80.10 o C; the K is 2.53 o C/molal. What is the molecular formula of the compound? C 3 H 9 Al C 12 H 36 Al 4 C 6 H 18 Al 2 C 9 H 27 Al 3 I am unsure and need to study this concept to prepare for the exam Question 4 What is the concentration of a 1.570 x 10 -6 M aqueous solution of AgNO 3 expressed in parts-per-million (ppm)? Assume a density of 1.00 g/mL. (MM of AgNO = 169.88 g/mol) 1.57 ppm 1.57 x 10 -3 ppm 2.67 x 10 -1 ppm 2.67 x 10 2 ppm 9.24 x 10 -3 ppm I am unsure and need to study this concept to prepare for the exam

Question 5 In the collision model, which factor is most sensitive to changes in temperature? The fraction of molecules with energy greater than the activation energy. The frequency of collisions that occur between reactant molecules. The orientation factor for a given reactant molecule. The magnitude of the activation energy for a given reaction. I am unsure and need to study this concept to prepare for the exam Question 6 Which solute (listed first) would be the least soluble in the given solvent (listed second)? Na 2 CO 3 in C 6 H 12 CH 3 CN in C 2 H 5 OH HF in H 2 O Br 2 in CCl 4 KCl in H 2 O I am unsure and need to study this concept to prepare for the exam Question 7 Taking ion-pairing into account, which of the following solutions should have the smallest ΔTf? 0.10 m NaCl 0.10 m CaCl 2 0.10 m K 2 SO 4 0.10 m MgSO 4 I am unsure and need to study this concept to prepare for the exam Question 8 A student obtains the following plots from data collected in lab. Which rate law below is the most likely for the reaction? rate = k rate = k[A] rate = k[A] 2 rate = k[A] 1/2 rate = k[A] -1 I am unsure and need to study this concept to prepare for the exam

Question 12 For a particular ionic substance, ΔH soln is +22 kJ/mol and ΔH mix is -629 kJ/mol. Estimate the magnitude of the lattice energy for the substance. (Disregard the enthalpy required to separate the water molecules.) 651 kJ/mol 22 kJ/mol 629 kJ/mol 607 kJ/mol I am unsure and need to study this concept to prepare for the exam Question 13 For the energy profiles shown below, which statement is true? Reaction X has the same activation energy in both the forward and reverse directions. Reaction Z has 1 intermediate and 2 transition states. Reaction W has the largest rate constant in the forward direction. Reaction Y is exothermic. I am unsure and need to study this concept to prepare for the exam

Question 14 The solubility of potassium dichromate is shown below: If 31 grams of K 2 Cr 2 O 7 is placed in 50.0 grams of water at 50 o C, what is the molality of the resulting solution? (MM of K 2 Cr 2 O 7 = 294.185 g/mol, MM of water = 18 g/mol) 0.51 m 1.0 m 1.3 m 2.1 m 0.78 m I am unsure and need to study this concept to prepare for the exam Question 15 The rate of disappearance of O 2 was measured and the following data was collected: Time (seconds) [O 2 ] (M) 0.0 2.30 30.0 1.65 60.0 1.23 90.0 1.01 120.0 0.95 Which time range has the greatest average rate? t = 0.0 s to t = 30.0 s t = 30.0 s to t = 60.0 s t = 60.0 s to t = 120.0 s t = 0.0 s to t = 120.0 s I am unsure and need to study this concept to prepare for the exam

Question 19 What is the mole fraction of heptane (C 7 H 16 ) in the vapor phase of a solution of 0.226 mol CBr 4 and 0.271 mol C 7 H 16 at 100°C? (Vapor pressures of pure substances at 100°C: CBr 4 = 47.2 torr; C 7 H 16 = 493.19 torr) 0.256 0.481 0.859 0.926 0.545 I am unsure and need to study this concept to prepare for the exam Question 20 Which of the following solutes would be the least soluble in the given solvent? NaCl in CCl 4 CH 3 OH in H 2 O NH 4 F in H 2 O Br 2 in C 6 H 6 I am unsure and need to study this concept to prepare for the exam