101, CHEM Spring 2006 Exam for 3rd Exam (April 18, 2005) 1. According to VSEPR theory, which one of the following molecules should be nonlinear? A. CO2 B. SO2 2. C. TeCl2 D. HCN
6.
For a particular process q = 20 kJ and w = 15 kJ at constant pressure. Which of the following statements is true? A. B. C. D. Heat flows from the system to the surroundings The system does work on the surroundings E = 35 kJ All of the above are true
According to VSEPR theory, which one of the following molecules has a tetrahedral shape? A. B. C. D. E. NH3 CCl4 CO2 SO3 HCN
7.
The Hfusion for sulfur is 17.7 kJ/mol. How many grams of sulfur can be melted by 29.0 kJ of energy? A. 9.8 g B. 26.2 g C. 52.5 g D. 40.7 g
8.
What hybridization do you expect for the central atom in PCl5? A. sp3d2 C. sp3d E. sp3 B. sp2 D. sp
3.
Which represents a valid Lewis structure for dinitrogen tetroxide, N2O4? 9.
An atom has two hybrid orbitals arranged in a linear geometry. Which of the following statements is true? A. The atom has one p orbital available for pi bonding. B. The atom has two p orbitals available for pi bonding. C. The atom has no pi orbitals. D. The atom has an s orbital available for sigma bonding.
10. Consider the following reaction: C2H5OH(l) + 3O2(g) CO2(g) + 3H2O 4. Sulfur atoms in the gas phase condense to form covalently bonded sulfur molecules via the reaction depicted below. Which statement about this process is true? 8S (g) S8 (g) H = - 1370 kJ. When a 15.1 g sample of ethyl alcohol (C2H5OH) is burned, how much energy is released as heat? A. 0.449 kJ C. 449 kJ B. 2250 kJ D. 1020 kJ E. 196 kJ
A. Energy is released as bonds are formed. B. Energy is required to form bonds. C. The energy of the reactants is the same as that of the products. D. Cannot tell from the information given.
11. What is the sign of H2O (g) H2O(l) A. B. C. D.
H for the following process.
5.
The H-C-C angle in C2H4 is: A. B. C. D. 90 109 120 180
positive, the process is endothermic negative, the process is endothermic positive, the process is exothermic negative, the process is exothermic
12. The bond in which one of the following pairs of atoms would be the most polar? A. B - C B. C - N C. C - O D. Si - O E. C - C
18. Find the standard enthalpy of formation of ethylene, C2H4(g) given the following data: 2C(s) + 2H2(g) C2H4(g) H f = ?
13. According to the VSEPR theory, the molecular geometry of the carbonate ion, CO32 , is A. square planar. B. tetrahedral. C. trigonal planar. D. trigonal pyramidal. E. octahedral.
C2H4(g) + 3O2(g) 2CO2(g) + H 2H2O(l) = 1411 kJ C(s) + O2(g) CO2(g) H f = 393.5 kJ H2(g) + 1/2O2(g) H2O(l) H f = 285.8kJ A. B. C. D. E. 52 kJ 87 kJ 731 kJ 1410 kJ 2770 kJ
14. Which of the following is the best Lewis structure for the nitronium ion (NO2 +)?
.. : O N O:
.. .. .. : O N O: ..
+
+
19. At STP, 2.75 liters of a gas has a mass of 5.39 grams. The gas is: A. N2 B. N2O C. NO D. NF3
A.
B.
C.
.. : O N O:
.. .. O N O .. ..
+
+
20. What mass of propane, C3H8(g), must be burned to supply 2580 kJ of heat? The standard enthalpy of combustion of propane at 298 K is 2220 kJ mol 1. A. 25.6 g B. 51.2 g C. 102 g D. 75.9 g E. 37.9 g
D.
21. The following drawing is a representation of a reaction for which H = +102 kJ. This reaction is likely 15. The formal charge on the Cl atom in the ClO2 ion is: A. 0 B. +1 C. 1 D. +2 E. +3
16. What hybridization do you expect for the central atom in NH3? A. sp3d2 B. sp3d C. sp3 D. sp2 E. sp
A. nonspontaneous at all temperatures B. nonspontaneous at low temperatures and spontaneous at high temperatures C. spontaneous at low temperatures and nonspontaneous at high temperatures D. spontaneous at all temperatures
17. The enthalpy change for the reaction 2HF(g) H2(g) + F2(g) 22. An empty 2.0 liter soda bottle is tightly capped at 22 C and 650 mmHg. If the bottle is placed in water at 95 C, what is the pressure in the bottle? A. 520 mmHg B. 780 mmHg C. 930 mmHg D. 810 mmHg
is 542.2 kJ. The enthalpy of formation of HF(g) in kilojoules per mole must be A. 542.2. B. 271.2. C. 135.6. D. 135.6. E. 271.2
23. Gaseous C2H4 reacts with O2 according to the following equation: C2H4(g) + 3O2(g) 2CO2(g) + 2H2O(g) What volume of oxygen at STP is needed to react with 1.50 mol of C2H4? A. B. C. D. E. 4.50 L 33.6 L 101 L 67.2 L 45 L
25.
If the process shown is spontaneous, what are the relative thermodynamic values? A. B. C. D. G , G +, G +, G , H , and H , and H +, and H +, and S S S S+
24. An atom has three hybrid orbitals arranged in a trigonal planar geometry. Which of the following statements is true? A. B. C. D. The atom has one p orbital available for pi bonding. The atom has two p orbital available for pi bonding. The atom has no p orbitals available for pi bonding. The atom has an s orbital available for sigma bonding.
26. With valve A closed and valve B open in the accompanying diagram of an open-end manometer, what can one say about the pressure of the gas in the bulb?
B
A. B. C. D.
Less than atmospheric pressure Same as atmospheric pressure More than atmospheric pressure Cannot tell from the diagram