Exam 2

Name _____Mr. Perfect________________________________ Date __F 14_______
1. If the n quantum number of an atomic orbital is equal to 2, what are the possible values
of l ? What are the possible values of ml if the quantum number l is equal to 3? (5 pts)
l ranges from 0 to n-1
ml
0, 1
-3, -2, -1, 0, 1, 2, 3
2. Give the notation (using letter designations for l ) for the sub-shells denoted by the
following quantum numbers. (10 pts)
a) n = 2 , l = 0
b) n = 3 , l = 2
2s
c) n = 4 , l = 3
3d
4f
d) n = 1 , l = 0
1s
3. Write both the electron configurations and the orbital diagrams for the following
elements in their ground states. Also, state if the element is paramagnetic or diamagnetic.
(20 pts)
a) 35Br
[Ar] 4s23d104p5
[Ar] [↑↓] [↑↓][↑↓][↑↓][↑↓][↑↓] [↑↓][↑↓][↑ ]
4s
3d
4p
Paramagnetic
b) 4Be
1s22s2
[↑↓] [↑↓]
1s 2s
Diamagnetic
c) 14Si
[Ne] 3s23p2
[Ne] [↑↓] [↑ ][↑ ][ ]
3s
3p
Paramagnetic
d) 10Ne
1s22s22p6
[↑↓] [↑↓] [↑↓][↑↓][↑↓]
1s 2s
2p
Diamagnetic
Chemistry 101 Exam 2
Name _____Mr. Perfect________________________________ Date __F 14_______
4. Use the Rydberg equation to calculate the wavelength (in nm) of a photon when a
hydrogen atom undergoes a transition from n = 3 to n = 5. Clearly state if light was
absorbed or emitted in this transition. Would this transition occur in the infrared or
ultraviolet region of the electromagnetic spectrum? R = 1.0967 x 107 m-1 (15 pts)
1

 R(
1
1
 2)
2
n1 n2
n2 > n1
(
(
)
)
Light was absorbed
5. If ΔE for an electronic transition in a hydrogen atom is –3.029 x 10-19 J, find nf if
ni = 3. RH = 2.179 x 10-18 J (10 pts)
E   RH (
1
1
 2)
2
n f ni
(
)
(
√
Chemistry 101 Exam 2
)
Name _____Mr. Perfect________________________________ Date __F 14_______
6. An experiment shows a 113 mL gas sample has a mass of 0.171 g at a pressure of 721
mmHg and a temperature of 32 °C. Find the molar mass of the gas. (10 pts)
R = 0.0821 L atm/mol K
PV = nRT
T = 32 + 273 = 305 K
P = 721 mmHg x 1 atm/760 mmHg = 0.9486 atm
)(
)
(
(
)(
(
)
)
What volume will one mole of the above gas mixture occupy at STP? (5 pts)
STP (Standard Temperature and Pressure) 1 atm and 0 °C (273 K)
(
)(
)(
)
7. Mothballs are composed primarily of the hydrocarbon naphthalene (C10H8). When
1.025 g of naphthalene is burned in a bomb calorimeter, the temperature of the
calorimeter rises from 24.25 °C to 32.33 °C. Find ΔErxn (kJ/mol) for the combustion of
naphthalene. The heat capacity of the calorimeter is 5.86 kJ/ °C. (10 pts)
Qcal = Ccal ΔT
Qcal = 5.86 kJ/°C(32.33 °C – 24.25 °C) = 47.3 kJ
Qcal = - Qrxn
Qrxn = -47.3 kJ
1.025 g x 1mol/128g = 8.01 x 10-3 mol
Chemistry 101 Exam 2
Name _____Mr. Perfect________________________________ Date __F 14_______
8. Given the following data:
Reverse
2O3(g) → 3O2(g)
ΔH° = -427 kJ
2x
NO(g) + O3(g) → NO2(g) + O2(g) ;
ΔH° = -199 kJ
Reverse
O2(g) → 2O(g)
ΔH° = 495 kJ
;
;
Calculate the ΔH° for the following reaction: (10 pts)
NO(g) + O(g) → NO2(g)
3O2(g)
→
2O3(g)
ΔH° = ?
427 kJ
2NO(g) + 2O3(g) → 2NO2(g) + 2O2(g)
-398 kJ
2O(g) → O2(g)
-495 kJ
2NO(g) + 2O(g) → 2NO2(g)
-466 kJ
NO(g) + O(g) → NO2(g)
ΔH° = -233 kJ
9. The first ionization energies of As and Se are 0.947 MJ/mol for As and 0.941 MJ/mol
for Se. Explain this result using orbital diagrams. (5 pts)
As [Ar] [↑↓] [↑↓][↑↓][↑↓][↑↓][↑↓] [↑ ][ ↑ ][↑ ]
4s
3d
4p
Se [Ar] [↑↓] [↑↓][↑↓][↑↓][↑↓][↑↓] [↑↓][↑ ][↑ ]
4s
3d
4p
The periodic trend would predict Se to have a higher ionization energy than As but the
reverse is true. This is due to the electron-electron repulsion in the 4p orbital of Se.
10. (Extra Credit) A system releases 415 kJ of heat and does 125 kJ of work on the
surroundings. What is the change in internal energy of the system? (5 pts)
ΔE = q + w = (-415 kJ) + (-125 kJ) = -540 kJ
Chemistry 101 Exam 2