Download Exam 1

CHM136 Exam 1Review Sheet
Exam 1 will cover chapters 6 and 5 in the Tro text. The topics from each chapter that may appear on the exam are
listed below briefly. Following that there are several example problems that you can solve as practice in preparation
for the exam. The answers to all the questions appear at the end of the problem set.
Chapter 6
Chapter 5
Energy: units and types
Boyle’s Law (P1V1=P2V2)
Heat (q)
Charles’s Law (V1/T1 = V2T2)
Heat capacity
General Gas Law (PV/T = c)
Calorimetry
Ideal Gas Law (PV = nRT)
Heat of reaction
R = 0.0821
atm⋅L
mol⋅K
Phase changes
Gas Mixtures (Pt = P1+P2+…)
Enthalpy
Kinetic Mol. Theory
Hess’s Law of Heat Summation
Stoichiometry w/ Gases
Diffusion and Effusion
1. How many joules are equivalent to 235 calories?
2. If 1.00 mole of ethanol, CH3CH2OH, at 22.0 °C absorbs 1.45 kJ of heat, what is the final temperature
of the ethanol? The specific heat capacity of ethanol is 2.44 J/g·K.
3.
If 46.1 g Zn at 18.0 °C is placed in 80.0 g H2O at 75.0 °C, what is the final temperature of the
mixture? The specific heat capacities of zinc and water are 0.388 J/g·K and 4.184 J/g·K, respectively.
4. When 27.0 g of an unknown metal at 88.4 °C is placed in 115 g H2O at 21.0 °C, the final temperature
of the water is 23.7 °C. What is the specific heat capacity of the metal? The specific heat capacity of
water is 4.184 J/g·K.
5. A 4.25 g sample of cyclohexane (C6H12) is combusted in a bomb calorimeter with a total heat
capacity of 5.86 kJ/ ºC. The temperature of the calorimeter increases from 23.5 ºC to 39.8 ºC. What
is the heat of combustion for cyclohexane in kJ/ mol?
6. Which of the following substances (with specific heat capacity provided) would show the greatest
temperature change upon absorbing 100.0 J of heat?
A) 10.0 g Ag, CAg = 0.235 J/g°C
B) 10.0 g H2O, CH2O = 4.18 J/g°C
C) 10.0 g ethanol, Cethanol = 2.42 J/g°C
D) 10.0 g Fe, CFe = 0.449 J/g°C
E) 10.0 g Au, CAu = 0.128 J/g°C
7. The thermochemical equation for the combustion of hexane is shown below.
2 C6H14(g) + 19 O2(g) → 12 CO2(g) + 14 H2O(g)
ΔH° = -8326 kJ
What is the enthalpy change for the combustion of 2.50 g C6H14?
8. Determine the heat of reaction for the oxidation of iron,
4 Fe(s) + 3 O2(g) → 2 Fe2O3(s)
given the thermochemical equations below.
2 Fe(s) + 6 H2O(l) → 2 Fe(OH)3(s) + 3 H2(g) ΔH = +321.8 kJ
2 H2O(l) → 2 H2(g) + O2(g)
ΔH = +571.7 kJ
Fe2O3(s) + 3 H2O(l) → 2 Fe(OH)3(s)
ΔH = +288.6 kJ
9. Use the ΔH°f information provided to calculate ΔH°rxn for the following:
SO2Cl2(g)
H2O(l)
HCl(g)
H2SO4(l)
SO2Cl2 (g) + 2 H2O(l) → 2 HCl(g) + H2SO4(l)
ΔH°f (kJ/mol)
-364
-286
-92
-814
ΔH°rxn = ?
o
for the combustion of gaseous ethanol,
10. Calculate ΔH rxn
C2H5OH(g) + 3 O2(g) → 2 CO2(g) + 3 H2O(g)
using standard molar enthalpies of formation.
molecule
ΔHfº (kJ/mol)
C2H5OH(g)
-235.3
CO2(g)
-393.5
H2O(g)
-241.8
11. The standard molar enthalpy of formation of NH3(g) is -45.9 kJ/mol. What is the enthalpy change if
5.38 g N2(s) and 3.32 g H2(g) react to produce NH3(g)?
12. The lid is tightly sealed on a rigid flask containing 3.50 L H2 at 17 °C and 0.913 atm. If the flask is
heated to 71 °C, what is the pressure in the flask?
13. A 0.225-L flask contains CH4 at 27 °C and 318 mm Hg. What is the pressure of the CH4 if the volume
is increased to 0.500 L and the temperature increased to 95 °C?
14. If a 3.44-L flask of SO2 at 1.65 atm contains the same number of molecules as a 5.00-L flask of H2 at
-7 °C and 1.00 atm, what is the temperature (in °C) of the SO2?
15. A 50.0 L cylinder of Ar has a pressure of 137 atm at 25 °C. What mass of Ar is inside the cylinder?
(R = 0.08206 L·atm/mol·K)
16. What volume of O2(g), measured at 17.7 °C and 0.978 atm reacts with 15.1 g C4H10 to produce
CO2(g) and H2O(λ)? (R = 0.08206 L·atm/mol·K)
17. How many moles of helium are found in a balloon that contains 5.5 L of helium at a pressure of
1.15 atm and a temperature of 22.0 ºC?
18. (This is a challenging one.) Acetylene may be produced from
the reaction between calcium carbide and water. How many
moles of acetylene are present in a 500.0 mL sample of gas
collected over water at 20.0 ºC and a total pressure of 758 torr?
The vapor pressure of water at 20.0 ºC is 17.54 mm Hg.
Answers: (1) 983 J (2) 34.9 °C
(3) 72.1 °C
(4) 0.74 J/g·K
(5) -1890 kJ/molJ
(6) E) 10.0 g Au, CAu = 0.128 J/g°C
(7) -121 kJ (8) -1648.7 kJ
(9) – 62 kJ (10) -1277.1 kJ
(11) -17.6 kJ
(12) 1.08 atm
(13) 176 mmHg
4
(16) 41.2 L
(17) 0.26 mol
(18) 0.0203 mol
(14) 29 °C
(15) .12 × 10 g