The City College of New York Chemistry Department Chemistry 10301, Sections T* Prof. T. Lazaridis Final examination, Dec 17, 2013 Last Name:____________________________ First Name: _______________________ Instructions: Do not cheat during this examination. You will automatically fail and may face
further action. * Write your answers clearly in pen. Exams will not be regraded if the work and
answer are not legible. * Questions are on both sides of each piece of paper. * You may tear off
the last sheet, which contains the periodic table. Do not write any answers or work on the last
page. It will not be counted during grading. * Use a calculator. No Cellphones or devices for
email/texting. * Please do not leave the room during the exam. If you must leave to go to the
bathroom, please give the exam to the Professor. * Place your student ID on the desk in front you
To guarantee full marks, you must SHOW WORK/REASONING, even for multiple choice
questions. No work or reasoning means no points.
Constants: Speed of light : 2.9979 X 108 m/s Planck's constant : 6.626 X 10-­‐34 Js Avogadro’s number: 6.022X1023 R= 0.0821 L atm/mol K = 8.3145 J/mol K = 62.364 L torr/mol K Some equations: c= λν ΔE = hν = -­‐2.18 X 10-­‐18 J Q = m c ΔT = C ΔT (c: specific heat, C: heat capacity) Score: 1._____ 2._____ 3._____ 4._____ 5._____ 6._____ 7._____ 8._____ 9._____ 10._____
11.____ 12._____
Total: _____
1. (10) a. (2) Write the formula of iron(II) phosphate ____________
b. (2) Name the compound P4S3 ___________
c. (2) How many protons and electrons does the Zn2+ ion have?
Protons ________ Electrons __________
d. (2) Write the atomic symbols of the elements Aluminum, Titanium, Potassium, Iodine.
e. (2) What is the oxidation number of Br in Br2
: _________ and BrO3- : _________
2. (6) Cortisone (a hormone composed of C,H, and O) is found to be 70.00% C, 7.83% H,
and 22.17% O by mass.
a. (4) Determine the empirical formula of the hormone
b. (2) The molar mass of the hormone is 360.5 g/mol. Determine its molecular formula
3. (4) Calculate the molarity of a phosphoric acid (H3PO4) solution if 36.25 mL of 0.1256
M sodium hydroxide neutralizes a 50.00 mL sample of the acid.
4. (4) A 2.55X105 -mL sample of butane (C4H10) gas at 150 oC and 1655 torr is burned
with an excess of oxygen to produce CO2 and H2O vapor. Calculate the pressure of CO2
in torr if the reaction products were collected in a 4000.0-L vessel at 15 oC.
5. (4) A typical microwave oven uses radiation with a 12.2-cm wavelength. When a
sample of water is irradiated with 2.00X105 moles of microwave photons, its temperature
rises from 22.0 oC to 99.8 oC. Calculate the mass of the water sample in grams. The
specific heat of water is 4.2 J/g oC.
6. (15) Combustion of trinitrotoluene (TNT) takes place according to the equation
4C7H5N3O6 (g) +21 O2 (g) -> 6N2 (g) + 28 CO2 (g) + 10H2O (g) ΔHo = -1.32X104 kJ
a. (3) During the constant pressure combustion of 4 moles of TNT, 1400 kJ of work is
done by the reacting system on its surroundings. What is the value of q, w, and ΔE for the
reaction?
b. (3) How many moles of CO2 are produced during the reaction that occurs when 600.0
g of TNT is mixed with 550.0 g of O2?
c. (3) The above reaction in part b produced 320.0 g of CO2. Calculate the percent yield
of CO2.
d. (3) How many kJ of heat will be released during the reaction in part b?
e. (3) The molar enthalpies of formation of CO2 (g) and H2O (g) are -393.5 kJ/mol and 241.8 kJ/mol, respectively. Calculate the molar enthalpy of formation of TNT in kJ/mol.
7. (9) a. (2) Is the wavelength of the photon absorbed by the transition of a hydrogen
electron from n=1 to n=3 longer than, shorter than, or equal to the wavelength of the
photon absorbed by the transition from n=3 to n=5?
Longer _______ Shorter ________Equal _______
b. (3) Write the abbreviated ground-state electron configuration of astatine (At)
c. (2) Show the orbital diagram of phosphorus (valence shell only)
c. (2) Is the cadmium(II) ion (Cd2+) paramagnetic or diamagnetic?
Paramagnetic _____
Diamagnetic _____
8. (8) a. (2) Circle the species with the largest radius
N P3- S2-
b. (2) Circle the species with the largest ionization energy Mg2+ Sr
c. (2) Circle the most electronegative element
Se Br
Cs
Bi
d. (2) Circle the element with the most metallic character Al
Cl
Rb
9. (10) Urea, CO(NH2)2 is made by the reaction of CO2 and ammonia:
O
||
O=C=O + 2NH3 -> H2N-C-NH2 + H2O
ΔHo=37 kJ/mol
a. (4) Given the following information
Bond
Bond energy (kJ/mol)
C=O
802
N-H
391
O-H
463
Calculate the C-N bond energy
b. (2) Would you expect your answer from part a to be greater than, smaller than, or equal
to the bond energy of C≡N? ___________
c. (4) Calculate the total volume of CO2 and NH3 at 200.0 atm and 450 oC that is required
to produce 2.50X103 g of urea.
10. (10) a. (3) Draw the Lewis structure for SO2Cl2 that satisfies the octet rule, indicating
the formal charge on each atom. (Hint: S is the central atom)
b. (3) Write the resonance structure for SO2Cl2 that has zero formal charge on each atom.
c. (4) Indicate the molecular geometry of the above molecule and the approximate value
of the bond angles. Which of the six bond angles do you expect to be the smallest?
11. (10) a. (2) What is the hybridization of each C in the molecule CH3-CH=CH-CH2OH
From the left: First C_____ Second C ______ Third C_______Fourth C ________
b. (2) How many π bonds are in the above molecule? ______
c. (2) Use molecular orbital theory to predict whether B2 or B2+ is more stable. (The
energy ordering of molecular orbitals is σ2s < σ*2s < σ2p < π2p < …)
d. (2) What is the bond order of B2 and B2+ ?
B2 : ________
B2+: ________
e. (2) Circle the species you expect to have the shorter bond:
B2
B2+
-
12. (10) a. (4) Predict the molecular geometry of the ion SCN using the VSEPR method
(C is the central atom).
b. (3) Predict the molecular geometry and the bond angles of the molecule PCl3 using the
VSEPR method
c. (3) Is the molecule Br2CH2 polar or nonpolar? Justify your answer.