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Unformatted text preview: Sample Midterm 2 Exam Part 1: Multiple Choice.
(5 pts each, 40 pts total)
Instructions: Bubble in the correct answer on your Scantron™ form AND circle the answer on your
exam. Each question has one correct answer.
1.) The answer to question 1 is A. Bubble in A on your Scantron™ form. 2.) To which orbital does the plot of |ψ|2 vs φ correspond?
A.) 1s B.) 2s C.) 2px D.) 2py E.) 2pz 2 |ψ | 0
0 3.) B.) H (2s) C.) H (4s) D.) He+ (4s) E.) He+ (8s) Identify the atom or ion with the electronic configuration [Ne]3s3p6?
A.) Ar+ 5.) 2π The ionization of which with UV light at 90 nm will produce electrons with the longest de Broglie
A.) H (1s) 4.) φ B.) K+ C.) Ar E.) Cl– D.) K Which has the largest atomic or ionic radius?
A.) Ar+ B.) K+ C.) Ar D.) K E.) Cl– Page 2 of 4 6.) Which is the most electronegative?
A.) H 7.) Name: _________________________________________ B.) Na C.) K D.) Cl E.) Br Which is not paramagnetic in its ground state?
2p A.) O B.) O– C.) O2– E.) O2– D.) O2 π2p
σ2p z σ*
O2 8.) After diving, which ascent poses the gravest danger to a diver holding his or her breath?
A.) 10m→0m B.) 20m→10m
D.) 60m→30m C.) 40m→20m
E.) 100m→40m water 10 m The atoms or molecules of which ideal gas have the greatest average kinetic energy?
A.) Ar at 200 °C B.) He at 400 °C D.) H2 at 200 °C C.) He at 100 °C E.) H2 at 100 °C 10 m 2 atm
3 atm 9.) air Page 3 of 4 Name: _________________________________________ Part 2: Short Answer Problems (105 pts total)
Instructions: Enter answers in the boxes provided. Show your work and justify your answer.
Consider the H atom and He+ ion.
a) What is the maximum wavelength of light that will ionize H(2s)? E = hc / λ = -R∞(Z2 / n2)
λ = h c n2 / R∞ Z2 = 364 nm b) Answer:
364 nm Light of what wavelength will induce the n=4 → n=8 transition in He+? ∆E = -R∞ Z2 ( 1/nf2 + 1/ni2 )
∆E = h c /λ
486 nm λ = h c / ( -R∞ Z2 )( 1/nf2 + 1/ni2 )
= 486 nm
Consider an atom of the element aluminum (Al) in its ground state.
a) Write the electron configuration for an atom of Al.
[Ne] 3s2 3p1 b) Write down the values of the quantum numbers for an electron in the highest occupied orbital.
n: 3 l: 1 ml: -1 or 0 or 1 ms: -½ or ½
c) Sketch the highest occupied atomic orbital and indicate number and type of nodes.
2 nodes total:
1 angular node
1 radial node Answer:
radial node angular node Page 4 of 4 Name: _________________________________________ (25 pts)
Consider 4.4 g of a hydrocarbon (hc) gas with the empirical formula C3H8.
a) The hydrocarbon fills a balloon to 0.56 L at 4.4 atm and 300 K. What is the molecular formula of
the hydrocarbon? P V = n R T ; n = mass / M
P V = (mass / M) R T Answer:
C3H8 M = mass R T / P V = 44 g/mol
b) Shown is a plot of the molecular speed distribution, F(v), and vrms for CO2 at 300 K. Sketch F(v)
and indicate vrms for the hydrocarbon gas at 300 K and 600 K.
hc at 300 K K
CO2 at 300 CO2 at 300 K
vrms 0.0025 vrms 0.0025 hc at 600 K
0.0025 (The same as CO2) F(v) F(v) 0.0000 0 500 1000 1500 2000 0.0000 v (m/s) vrms ≈ 583 m/sec F(v) 0 500 1000 1500 2000 v (m/s) 0.0000 0 500 1000 1500 2000 v (m/s) (25 pts)
Two sunscreen products (X and Y) have the following extinction coefficients, ε, at 310 nm:
X = 3.0 cm2/g and Y = 1.0 cm2/g. For the following questions, the absorbance should be
calculated for a 1 cm sample path length.
a) What is the absorbance of a 0.1 g/mL sample of X? A = ε l c = 0.3 b) Answer:
0.3 A 0.10 g/mL sample of either X or Y is placed in the spectrometer. The measured ratio of the
intensity of the transmitted light to the intensity of the incident light is 0.80 at 310 nm. Is the
sample sunscreen X or Y? A = log (Io / It) = ε l c
ε = [ log (Io / It) ] / l c = 1.0 cm2/g Answer:
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This note was uploaded on 09/11/2009 for the course CHEM 1A taught by Professor Nitsche during the Spring '08 term at Berkeley.
- Spring '08