CHEMISTRY 1031 EXAM III QUESTIONS FOR THE REVIEW WORKSHOP (You will need a periodic table. Useful information is on page 4. Answers are on page 5.

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1 CHEMISTRY 1031 EXAM III QUESTIONS FOR THE REVIEW WORKSHOP (You will need a periodic table. Useful information is on page 4. Answers are on page 5.) 1 1. Calculate the minimum energy required to decompose 765 g of PCl 3, according to the reaction: 4 PCl 3 (g) P 4 (s) + 6 Cl 2 (g) ΔH o rxn = kj. The molar mass of PCl 3 is g/mol. 2. The reaction: 2 K(s) + 2 HBr(aq) 2 KBr(aq) + H 2 (g) has an enthalpy of 315 kj per mole of potassium. If 3271 J of heat are produced, how many grams of potassium reacted? 3. Use the standard reaction enthalpies given below to determine ΔH o rxn for the following reaction: 2 NO(g) + O 2 (g) 2 NO 2 (g) ΔH o rxn =? Given: N 2 (g) + O 2 (g) 2 NO(g) ½ N 2 (g) + O 2 (g) NO 2 (g) ΔH o rxn= +183 kj ΔH o rxn = +33 kj 4. Use the ΔH o f and ΔH o rxn information provided to calculate ΔH o f for SO 3 (g): 2 SO 2 (g) + O 2 (g) 2 SO 3 (g) ΔH o rxn = 198 kj ΔH o f SO 2 (g) = 297 kj/mol 5. A ml sample of M NaOH(aq) is mixed with a ml sample of M HNO 3 (aq) in a coffee-cup calorimeter. If both solutions were initially at C and the temperature of the resulting solution was recorded as C, determine the value of ΔH o rxn, in kj/mol, for this neutralization reaction. Assume that no heat is lost to the calorimeter or the surroundings, and that the density of the solution is 1.00 g/ml and its specific heat capacity is J/g C. 6. A 1.00 g sample of coffee beans was completely combusted in a bomb calorimeter with a total heat capacity of 62.1 J/ o C) and caused the temperature of the water in the calorimeter to increase from K to K. (a) What is the change in temperature of the water in Celsius? (b) Calculate the heat released by the coffee beans in Joules. (c) If one cup of black coffee is made from 237 g of coffee beans, how many Calories are in one cup of black coffee? 7. To calibrate a bomb calorimeter, a g sample of glucose (molar mass = g/mol) was combusted, causing a temperature increase of the calorimeter and its contents of 5.70 C. If the combustion of 1.00 mole of glucose releases 2.82 x 10 3 kj of heat, what is the heat capacity, in J/ o C, of the calorimeter and its contents? 8. After calibration of the calorimeter in problem 7, g of glucose was combusted. What would be the change in temperature of the calorimeter and its contents? 9. How much energy, in kj/mol, would be required to completely remove the electrons from 1.00 mole of hydrogen atoms, i.e., for: H H + + e, when the electrons are in the ground state?

2 10. If an electron in a hydrogen atom jumps from level n = 6 and emits one photon of energy 4.85 x J, what level does the electron jump to? In 2009 the Jamaican sprinter Usain Bolt (nicknamed the lightning bolt ) ran the 100 m race in a world-record time of 9.58 s. Bolt weighs 86 kg. What was Bolt s wavelength in meters? What type of electromagnetic radiation would this wavelength be associated with? 12. Which set of quantum numbers cannot occur together to specify an orbital? A. n = 2, l = 1, m l = 0 C. n = 3, l = 2, m l = 3 B. n = 3, l = 2, m l = 0 D. n = 2, l = 0, m l = Which of the following orbitals can exist in an atom? A. 3f B. 5p C. 1d D. 4g 14. How many electrons can have the quantum numbers n = 4 and l = 3? A. 14 B. 10 C. 7 D The total number of nodes in a 4s orbital is: A. 4 B. 3 C. 2 D Which of the following visible colors of light has the lowest frequency? A. red B. blue C. yellow D. orange 17. Which of the following forms of electromagnetic radiation has the longest wavelength? A. gamma rays B. infrared C. X-rays D. ultraviolet 18. What is the expected electron configuration for osmium (Os) in its ground state, and how many unpaired electrons are in an atom of osmium? 19. Which of the following transition metal cations is diamagnetic? A Ti 2+ B. Cr 3+ C. Co 2+ D. Cu + Use the following electron configurations to answer questions A. 1s 2 2s 2 2p 3 x 2p 0 0 B. 1s 2 2s 2 2p 1 x 2p 1 1 C. 1s 2 2s 2 2p 2 x 2p 1 0 D. 1s 2 2s 2 2p 1 x 2p 1 y 2p 0 z 3s Which configuration does not obey Hund s rule? 21. Which configuration does not obey Pauli s exclusion principle? 22. Which configuration is that for the nitrogen in an excited state?

3 23. The electron configuration for an atom of sulfur in the ground state is: 3 A. 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 4p 2 B. 1s 2 2s 2 2p 6 3s 2 3p 6 C. 1s 2 2s 2 2p 6 D. 1s 2 2s 2 2p 6 3s 2 E. 1s 2 2s 2 2p 6 3s 2 3p 4 Use the electron configurations in question 23 to answer questions Which is the electron configuration of the S 2 anion? 25. Which is the electron configuration of the S 6 anion? 26. Which is the electron configuration of the S 4+ cation? 27. Which is the electron configuration of the S 6+ cation? 28. Which of the ions in questions would you expect to be the least stable? 29. The reason for your answer to question 28 is: A. the ion is not stable because it does not have a full shell B. the ion is not stable because it exceeds the number of electrons allowed C. the ion is not stable because electrons have been placed in a higher energy level D. the ion is not stable because the number of electrons does not equal the number of protons 30. Rank the following: Br As S B Ar N, in order of decreasing radii. A. Br > As > Ar > S > N > B C. Br > As > S > Ar > N > B B. N > B > Ar > S > Br > As D. As > Br > S > Ar > B > N 31. Rank the following: Al Mg P S, in order of increasing first ionization energy: A. Mg < Al < P < S B. S < P < Al < Mg C. Al < Mg < P < S D. Al < Mg < S < P 32. The reason for your answer to question 31 is: A. going across a period, ionization energies decrease due to electrons repelling one another B. going across a period, ionization energies increase due to electrons attracting one another C. going across a period, ionization energies increase due to a decrease in nuclear charge D. none of these reasons are correct 33. To which element do the following successive ionization energies, in kj/mol, belong? IE 1 = 1012 IE 2 = 1907 IE 3 = 2914 IE 4 = 4963 IE 5 = 6274 IE 6 = 21,267 IE 7 = 25,431 A. F B. Al C. P D. Cl

4 34. Electron affinity is defined as: 4 A. the tendency to attract electrons in a covalent bond B. the opposite of ionization energy C. the energy for the process: X(g) + e X (g) D. the energy for the process: X + (g) + e X(g) 35. Which of the following has the lowest (most negative) value of electron affinity? A. Ne B. F C. O D. N 36. Which of the following ions has the largest ionic radius? A. S 2 B. Cl C. K + D. Ca The reason for your answer to question 36 is: A. the ion chosen has the same number of electrons than the others but a smaller nuclear charge B. the ion chosen has the same number of electrons than the others but a greater nuclear charge C. the ion chosen has more electrons than the others D. the ion chosen has fewer electrons than the others Potentially Useful Information: 1 cal = J 1000 cal = 1 Cal Avogadro s Number = x mol 1 c = 3.00 x 10 8 m/s h = x J s mass e = x kg 1 J = 1 kg m 2 /s 2 E n = x J 2 n

5 ANSWERS kj 20 C g 21 A kj 22 D kj/mol 23 E kj/mol 24 B 6 (a) 2.56 o C (b) 159 J (c) 9.01 Cal 25 A J/ o C 26 D o C 27 C kj/mol 28 A 10 n = 2 29 A x m; no EM radiation has this 30 D 12 C 31 D 13 B 32 D 14 A 33 C 15 B 34 C 16 A 35 B 17 B 36 A 18 [Xe]4f 14 5d 6 6s 2 4 unpaired electrons 37 A 19 D