CHEM 101 Midterm: CHEM 101 Drexel CHEM 101 Exam 2 WINTER 08 09 VER. A with answers
CHEM 101 WINTER 08-09 EXAM II
On the answer sheet (Scantron) write you name, student ID number, and recitation section number. Choose the
best (most correct) answer for each question and enter it on your answer sheet.
Avogadro’s Number: 6.022 × 1023 mol-1
Speed of Light: c = 3.00 x 108 mys-1
Planck’s Constant: h = 6.626 x 10-34 Jys
Rydberg Constant: R = 2.179 x 10-18 J
E = hc/λ = hυ
q = m c ΔT
1 cal = 4.184 J
1. Please choose the letter “a” as your answer for this question.
2. Which statement about energy is false?
a. Chemical reactions are processes that transfer energy.
b. Thermodynamics is the science of working and heating processes.
c. The chemical energy of foods and fuels is a type of potential energy.
d. Working and heating are processes that transfer energy.
e. The thermal energy of nanoscale objects is a type of potential energy.
3. Determine the incorrect relationship given below.
a. 80.0 cal/g = 312 J/g
b. 1 μJ = 1 × 10−6 J
c. 1000 cal = 1 kcal
d. 1000 J = 1 kJ
e. 44.0 kJ = 1.05 × 104 cal
4. The First Law of Thermodynamics states that:
a. The total energy of the universe is constant.
b. The total entropy of the universe is increasing.
c. Molecules move faster as temperature increases.
d. Samples with different temperatures that come in contact with one another will reach
thermal equilibrium.
e. Energy transfers from hotter objects to cooler objects.
5. If heat is transferred from the system to the surroundings then
a. qs
y
ste
m
and q
s
urroundin
g
s are both negative
b. qs
y
ste
m
is positive and q
s
urroundin
g
s is negative
c. qs
y
ste
m
= q
s
urroundin
g
s = 0
d. qs
y
ste
m
is negative and q
s
urroundin
g
s is positive
e. qs
y
ste
m
and q
s
urroundin
g
s are both positive
6. Heating a 25.0 g sample of each substance below with 375 J of energy will cause which substance to have the
smallest increase in temperature?
a. water (specific heat = 4.184 J g−1 °C−1)
b. iron (specific heat = 0.451 J g−1 °C−1)
c. gold (specific heat = 0.128 J g−1 °C−1)
d. copper (specific heat = 0.385 J g−1 °C
−
1)
e. Not enough information to determine.
7. A 20.0 g sample of aluminum (specific heat = 0.902 J g−1 °C−1) with an initial temperature of 48.6°C is heated with
427 J of energy. What is the final temperature of the sample?
a. 76.8°C
b. 26.2°C
c. 72.3°C
d. 23.7°C
e. 24.9°C
8. What is the molar heat capacity of magnesium difluoride, MgF2 (specific heat = 1.00 J g−1 °C−1)?
a. 245 J mol−1 °C−1
b. 62.3 J mol−1 °C−1
c. 117 J mol−1 °C−1
d. 43.3 J mol−1 °C−1
e. 5.30 × 1022 J mol−1 °C−1
9. Determine the quantity of ice required to absorb exactly 50 kJ of energy when the ice warms from −50.0°C to
−10.0°C (specific heat of ice = 2.06 J g−1 °C−1).
a. 0.485 g
b. 607 g
c. 2.43 × 103 g
d. 485 g
e. 0.607 g
10. Which process is exothermic?
a. warming milk
b. subliming dry ice
c. evaporating alcohol
d. freezing rain drops
e. defrosting frozen food
11. Based on the following thermochemical equation, which statement is false?
NH3 (l) NH3 (g) H° = +23.4 kJ
a. The internal energy of the surroundings increases.
b. The enthalpy change for the gas condensing into a liquid is known.
c. The enthalpy change is endothermic.
d. The atmospheric pressure for the process is known.
e. The thermochemical equation represents a physical change.
Document Summary
On the answer sheet (scantron) write you name, student id number, and recitation section number. Choose the best (most correct) answer for each question and enter it on your answer sheet. Speed of light: c = 3. 00 x 108 m(cid:121)s-1. Planck"s constant: h = 6. 626 x 10-34 j(cid:121)s. Rydberg constant: r = 2. 179 x 10-18 j. E = hc/ = h q = m c t. 1: water (specific heat = 4. 184 j g. 1 c iron (specific heat = 0. 451 j g. 1: gold (specific heat = 0. 128 j g. 1 c: copper (specific heat = 0. 385 j g, not enough information to determine. 1) with an initial temperature of 48. 6 c is heated with: a 20. 0 g sample of aluminum (specific heat = 0. 902 j g. What is the final temperature of the sample: 76. 8 c, 26. 2 c, 72. 3 c, 23. 7 c, 24. 9 c. 1: 43. 3 j mol, 5. 30 1022 j mol.
