CHEM 101 Midterm: CHEM 101 Drexel CHEM 101 Exam 2 WINTER 09 10 VER. A no answers
CHEM 101 WINTER 09-10 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 ms-1
Planck’s Constant: h = 6.626 x 10-34 Js
Rydberg Constant: R = 2.179 x 10-18 J
E = hc/λ = hυ
q = m c ∆T
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.
Combustion reactions are exothermic processes.
c.
The bond energy of foods and fuels is a type of potential energy.
d.
Sublimation is an endothermic process.
e.
Vaporization is an exothermic process.
3. Determine the incorrect relationship given below.
a.
80.0 cal/g = 312 J/g
b.
1
µ
J = 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.
Since energy cannot be created or destroyed, the total energy of the universe is constant.
b.
The total entropy of the universe is increasing.
c.
In any process, the total change in energy of a system, ∆E, is equal to the sum of the heat,
q, and the work, w, transferred betwen the system and the surroundings.
d.
Samples with different temperatures that come in contact with one another will reach
thermal equilibrium.
e.
Both “a” and “c” above are correct.
5. If heat is transferred to the system from the surroundings then
a.
∆q
syste m
and ∆q
surroundings
are both negative
b.
∆qsyste m is positive and ∆qsurroundings is negative
c.
∆qsyste m = ∆qsurroundings = 0
d.
∆qsyste m is negative and ∆qsurroundings is positive
e.
∆q
syste m
and ∆q
surroundings
are both positive
6. A 25.0 kg sample of each substance below is cooled until each has released 25.0 kJ of energy. Which substance
will undergo the largest change 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. How much energy is required to raise the temperature of a 454.0 g sample of copper (specific heat = 0.385 J g−1
°C−1) from 60°C to 110°C?
a.
8.74 kJ
b.
8.74 x 103
µ
J
c.
8.74 J
d.
8.74 x 103 kJ
e.
None of the above answers is correct.
8. Solid sodium chloride, NaCl (s), has a molar heat capacity of 50.7 J mol−1 °C−1. What is the specific heat of sodium
chloride?
a.
58.5 J g−1 °C−1
b.
0.623 J g−1
°
C−1
c.
117 J g−1
°
C−1
d.
0.867 J g−1
°
C−1
e.
5.30 × 10
3
J g
−1
°C
−1
9. Determine the final temperature of 900 g of ice, initially at –40°C, after the release of exactly 45 kJ of energy. The
specific heat of ice is 2.06 J g−1 °C−1.
a.
+15.73°C
b.
–55.73
°
C
c.
–64.27
°
C
d.
–15.73°C
e.
+55.73°C
10. Which process is endothermic?
a.
cream becoming ice cream
b.
deposition of water vapor as frost
c.
condensation of alcohol vapor into liquid alcohol
d.
water turning into ice cubes
e.
a frozen pond becoming a lake
11. Based on the following thermochemical equation, which statement is false?
NH
3
(g) NH
3
(l)
H° = –23.4 kJ
a.
The energy of the surroundings increases.
b.
The heat of vaporization for ammonia is known.
c.
The equation represents an endothermic process.
d.
The pressure for the process is known.
e.
The thermochemical equation represents a change of physical state.
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 s-1. Planck"s constant: h = 6. 626 x 10-34 j 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: solid sodium chloride, nacl (s), has a molar heat capacity of 50. 7 j mol. 1 c: 0. 867 j g, 5. 30 103 j g. 1: determine the final temperature of 900 g of ice, initially at 40 c, after the release of exactly 45 kj of energy.
