Gen. Chem. - Chap. 8
Choose the correct answer for each question.
 

1A reaction which causes the surroundings to become hotter can be classified as what? What is the sign of dH for this reaction?
exothermic, +
exothermic, -
endothermic, +
spontaneous, -

2A 100. g sample of a certain metal absorbs 392.2 J of heat which causes the temperature of the metal to increase from 22.0C to 55.4C. Which of the following could be the metal? (c= specific heat)
Au (c = 0.129 J/g-C)
Cr (c = 0.449 J/g-C)
Ti (c = 0.523 J/g-C)
Al (c = 0.902 J/g-C)

3Given the following chemical equation...
2 H2 + O2 ----> 2 H2O dH = -571.6 kJ
What is dH when 5.25 g of H2O is formed?
-571.6 kJ
-108 kJ
-166.6 kJ
-83.3 kJ

42.60 g of NH4NO3 are dissolved in a coffee-cup calorimeter containing 62.1 g of H2O originally at 20.5C. Calculate the dH for the reaction if the final temperature of the H2O is 17.0C.
+234 J
-909 J
+909 J
-234 J

5Diethyl ether (C4H10O) is a compound that was once used an a general anesthetic. When 5.00g of diethyl ether is burned in a bomb calorimeter (Ccal = 10.10 kJ/C) the temperature goes up from 22.50C to 40.73C. Calculate the heat released per mole of C4H10O.
177 kJ/mol
184 kJ/mol
468 kJ/mol
2730 kJ/mol

6Given that dH is +3073 kJ for the following reaction, find the enthalpy change for the production of 8.0 mol of nitroglycerine, C3H5(NO3)3.
3 N2(g) + 1/2 O2(g) + 5 H2O(l) + 6 CO2(g) ----> 2 C3H5(NO3)3(l)
+3841 kJ
+12,290 kJ
-768.0 kJ
-1.45 kJ

7Calculate dH for the following reaction given dHf CaCl2 = -795.8 kJ/mol dHf Ca2+ = -542.8 kJ/mol and dHf Cl- = -167.2 kJ/mol
Ca2+(aq) + 2 Cl-(aq) ----> CaCl2
-81.4 kJ
+81.4 kJ
-85.8 kJ
-1506 kJ

8Which of the following substances has a dHf = 0 at 25C and 1 atm?
Na+ (aq)
H2O (l)
Cu (s)
HCl (g)

9Given the following thermochemical equations...
2 C(graphite) + 2 O2 ----> 2 CO2 dH = -786 kJ
C(diamond) + O2 ----> CO2 dH = -395.4 kJ

Calc. the dH for the conversion of graphite into diamond:
C(graphite) ----> C(diamond)
+2.4 kJ
-390.6 kJ
-1181 kJ
+47.5 kJ

1062 J of heat is absorbed by a system and 51 J of work is done on it. The system then does 80 J of work. What is the change in energy for the system?
+33 J
-91 J
+91 J
+193 J