C1151T4_N_13M (7/8/13)
CHEMISTRY 1151 TEST # 4 (Take Home) 4/22/14
Name ______________
GPC (Dunwoody; Dr. Kim’s Section)
Calculator & Model # __________________
Due 1:00 pm, 4/24/2014. Staple all papers EXCEPT the Red Scantron.
Please\leave the first column blank for the ID number section of the form.
Your work (calculations/explanations) must be given for full credits in the space.
You also need to fill the blanks.
1mi=1.609km; 1ft=30.48cm; 1lbs=453.6g; 1gal=3.785L; 1mL=1cm3; c=2.9979x108m/s;
1atm = 760 torr = 14.7psi ; 1mol=6.022x1023; 1cal=4.184J; R=0.08206L.atm/(K.mol).
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1. How many moles of Mg(OH)2 are contained in 1.00 lb (453.6g) of the compound?
(A) 11.0, (B) 8.70, (C) 7.78, (D) 6.92, (E) 5.87.
2. Which one of the following contains 9.06 x 1023 (=1.5 mole) atoms?
(A) 16.0 g O2 , (B) 4.00 g He, (C) 28.0 g N2, (D) 22.0 g CO2, (E) 8.0 g CH4.
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3. Iron is produced by reducing iron ore (hematite, Fe2O3) with carbon monoxide:
Fe2O3(s) + 3 CO(g) →
2 Fe(s) + 3 CO2(g)
Find molar mass (g/mol) of Fe2O3 and CO.
A(71.85, 28.01), B(71.85, 44.01), C(159.70, 28.01), D(159.70, 44.01), respectively.
4. The reaction above starts with 100g Fe2O3 and 100g CO. Moles of Fe2O3 & CO in each mass
are A(1.39, 2.27), B(1.39, 1.14), C(0.626, 3.57) D(3.57, 0.626), respectively.
5. How many moles of CO are needed, and how many moles of Fe can be produced from 1 mole
of Fe2O3(s) (A) 1 & 2, (B) 2 & 1, (C) 2 & 3, (D) 3 & 2, respectively.
Explain
6. How many moles of CO are needed from the given moles of Fe2O3(s) ?
(A) 0.219, (B) 0.626, (C) 1.25, (D) 1.39, (E) 1.88 moles.
7. Moles of CO present is (a) more, (b) less than needed: thus, the limiting reactant must be:
(c) Fe2O3 , (d) CO.
A(a,c), B(a,d), C(b,c). D(b,d).
8. The theoretical amount of Fe that can be produced from 100g of Fe2O3 & 100g of CO is
(A) 35 g, (B) 66 g, (C) 70 g, (D) 132 g, (E) 200 g.
9. Amount (in g) of the excess reactant left unreacted after the reaction is complete is
(A) 17.5, (B) 82.5, (C) 35.0, (D) 65.0, (E) 47.4 g.
10. Find a mass of CO2 to be generated.
(A) 9.6, (B) 27.5, (C) 55.0, (D) 61.2, (E) 82.3 g.
11. Find volume of CO2 generated at 25oC & 735 torr. (A) 40.7, (B) 43.5, (C) 44.5, (D) 47.6 L.
12. If an actual amount of iron produced above found to be 50 g. The % yield of Fe must be
(A) 25%, (B) 38%, (C) 71%, (D) 76%, (E) 143%.
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13. For oxidation of propane: (1) C3H8(g) + ( )O2(g)  ( )CO2(g) + ( )H2O(g) ΔH = -2,040kJ
Fill the blanks to balance it, then prove it.
Sum of all the coefficients is A(7), B(9), C(11), D(13), E(15).
14. The reaction above is a(Endothermic), b(Exothermic) because an enthalpy change (ΔH) of
the reaction is c(Positive), d(Negative).
A(a,c), B(a,d), C9b,c). D(b,d).
15. How much heat (kcal) is generated for combustion of 1.0 pound of propane gas?
A(2,400), B(3,600), C(5,000), D(7,200), E(9,600) kcal.
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16. An ideal gas molecule has only a a(Volume), b(Mass). A real gas behaves as if it is an ideal
gas at a c(Low), d(High) pressure and at a e(Low), f(High) Temperature.
A(a,c,e), B(a,c,f), C(b,c,e). D(b,c,f), E(a,d,e).
17. Which gas has a highest density (i.e., heaviest) ? A(H2), B(O2), C(N2), D(H2O), E(NO2).
Why? Explain it with calculation.
18. It is easier to hit a home-run in a (a) hot, (b) cold, and (c) dry, (d) humid, day. This is because
density of air becomes smaller, so a speed ball experience less resistance from the air molecules.
A(a,c), B(a,d), C(b,c), D(b,d).
19. Calculate a density (g/L) of a dry air at 25oC and 1.0 atm using the Ideal Gas Law Equation.
You need to find an average molar mass of the air first from the composition of the dry air:
78% N2, 21% O2, 1% Ar. The molar mass the air (in 3 Sig. Fig.) = (
) g/mol.
A(1.08), B(1.18), C(1.28), D(1.38) g/L.
Thus, the density of the air is about (
) times LESS than that of water (1.00g/mL).
20. A steel cylinder has a bursting point of 10,000psi. It is filled with gas at 2,500 psi and
at 20 oC. During transport it is exposed to a heat to reach 100oC.
(1) Find the new pressure. (2) Will it explode?
A(12,500 psi; Yes), B(12,500; No), C(3,200; Yes), D(3,200; No).
21. According to Avogadro’s Law, equal volumes of NH3 and N2, at the same temperature
and pressure have the same A(masses), B(density), C(# of atoms), D(# of molecules)
22. A gas mixture is made of He, N2, and O2.Their partial pressures are, respectively,
310 torr, 0.200 atm & 7.35psi. What is the total pressure? A(318), B(428), C(648), D(842) torr.
23. We human breathe 12 times a minute. During each breathing, 500 mL of air is taken to the
lung. The volume % ( = mole %) of O2 in inhaled and exhaled air are 20% and 15% each.
Find a volume of air which is actually absorbed in the lung and consumed with a single
Breadth assuming 25oC of temperature. A(5), B(25), C(50), D(75), E(100) mL/breadth.
24. Based on the answer above, estimate a mass (in ton) of O2 Mozart consumed during
36 years of his life.
About A(7), B(70), C(700), D(7,000) tons.
25. Upon a big collision, an air-bag in automobiles are inflated with N2 gas which is generated
from a rapid decomposition of sodium azide (a solid), NaN3 which is trigger by the shock:
2NaN3(s)  2 Na(s) +3 N2(g)
How many grams of NaN3 is needed to produce a bagful(75L) of N2 gas at 10.0oC & 760 torr.
(
) g. Answer in Three Significant Figures.