Sample Final Exam

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Houston Community College System. Chemistry 1305/ ... Sample Final Exam, Chapters 1 – 13 Corwin ... C) Test a hypothesis and state a theory or law. D) All of  ...
Houston Community College System

Chemistry 1305/1405 Sample Final Exam

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CHEM 1305/1405 Sample Final Exam, Chapters 1 – 13 Corwin PART I – Multiple choice (2 points each) DIRECTION- Please write your correct choice in the space provided. _____1. Which of the following is a basic step in the scientific method? A) Perform an experiment and collect data B) Analyze experimental data and propose a hypothesis C) Test a hypothesis and state a theory or law D) All of the above. _____2. Round off the following measurement to the three significant digits: 107.500 g A) 107 g

B) 108 g

C) 107.0 g

D) 107.4 g

_____3. Add 7.77 g to 51.665 g and round off the sum to the proper significant digits A) 59.0 g

B) 59.4 g

C) 59.43 g

D) 59.44 g

_____4. Express 0.000000000000000000000000000000010 as an exponential number. A) 1.0 X 10–10 B) 1.0 X 10–32 –33 C) 1.0 X 10 D) 1.0 X 1032 _____5. Which of the following is not a branch of chemistry? A) Analytical Chemistry B) Environmental Chemistry C) Physical Chemistry D) All are branches of chemistry -------6. Which of the following unit factors is derived from: 1 mile = 1760 yards? A) 1 mile/ 1 yard B) 1760 miles/ 1 yard C) 1760 yards/ 1 mile D) 1760 yard/ 1760 miles _____7. The radius of a tin atom is 1.41 X 10–8 cm. What is the radius of the atom in nanometers? 1 nm = 10–9 m, 1m = 102 cm A) 1.41 X 10–16 nm B) 1.41 X 10–10 nm C) 1.41 X 10–4 nm D) 1.41 X 10–1 nm _____8. A glass cylinder contains four separate liquid layers: mercury (d = 13.6 g/mL), chloroform (d = 1.49 g/mL), acetic acid (d = 1.05 g/mL), ether (d = 0.708 g/mL). If a marble (d = 3.05 g/mL) is added to the cylinder, where does it come to rest? A) On top of the mercury layer B) On top of chloroform layer C) On top of acetic acid layer D) On the top of ether layer _____9. A 50.0 g sample of solid aluminum releases 420.0 calories when cooled from 100.0°C to 60.0°C. What is the specific heat of the metal? A) 0.168 cal/(g°C) B) 0.210 cal/(g°C) C) 0.840 cal/(g°C) D) 4.76 cal/(g°C) 2

____10. Given that methanol freezes at –94°C, what is the freezing point temperature on the Kelvin scale? A) –367 K B) –179 K C) –94 K D) 179 K ____11. Which of the following elements is an example of a semimetal? A) H B) C C) Fe D) Ge ____12. Use the periodic table and predict which of the following elements a liquid at 25°C. A) B B) Ba C) Be D) Br ____13. How many neutrons are in the nucleus of one atom of oxygen–18? A) 2 B) 8 C) 10 D) 18 ____14. What is the maximum number of electrons that can occupy a 4d sublevel? A) 2 B) 4 C) 7 D) 10 ____15. The original periodic law was based on which of the following? A) Increasing atomic mass B) Increasing atomic number C) Increasing isotopic number D) Increasing mass number. ____16. Predict the boiling point for argon given the boiling points of Krypton (–152°C) and Xenon (–107°C). A) –197°C B) –130°C C) –62°C D) –45°C ____17. What is the electron configuration for a titanium (II) ion, Ti2+ ? A) [Ar] B) [Ar] 4s2 3d0 C) [Ar] 4s0 3d2 D) [Ar] 4s2 3d2 ____18. CO2 is classified as which of the following? A) Binary ionic B) Ternary ionic C) Binary molecular D) Ternary molecular ____19. What is the formula for the ionic compound composed of bismuth ion, Bi3+ and CN– ? A) BiCN B) BiCN3 C) Bi3CN D) Bi(CN)3 ____20. Which of the following is not evidence for a chemical reaction producing a gas? A) An odor is detected B) a solid white precipitate forms C) a flaming splint is extinguished D) a glowing splint bursts into flames ____21. What are the products from the following decomposition reaction? NiCO3 (s) → A) Ni and CO2 B) NiO and CO2 C) Ni2O3 and CO2 D) NiO, H2O, and CO2 ____22. How many methane molecules, CH4, have a mass of 3.2 g ? A) 1.20 X 1023 molecules B) 1.20 X 1024 molecules –24 C) 1.93 X 10 molecules D) 3.01 X 1023 molecules 3

____23. If 1.00 mol of krypton gas exerts a pressure of 1.00 atm at 100°C, what is the volume of the gas? (R = 0.08206 L atm./ mol K) A) 2.20 mL B) 8.21 L C) 12.2 L D) 30.6 L ____24. How many valence electrons are in a bromine atom and a bromide ion? A) 1 and 7, respectively B) 1 and 8, respectively C) 7 and 8, respectively D) 7 and 10, respectively. ____25. Which of the following ions has the following electron configuration? 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 ? A) I– B) S2– C) K+ D) Sr2+ ____26. Given the electronegativity values H = 2.1, N = 3.0, O = 3.5, and P = 2.1, which of the following molecules contains nonpolar covalent bonds? A) water, H2O B) Laughing gas, N2O C) phosphine, PH3 D) ammonia, NH3 ____27. What is the strongest intermolecular force in a liquid containing polar molecules? A) Covalent bonding B) Ionic bonding C) Dipole forces D) Dispersion forces ____28. What are the products from the complete combustion of a hydrocarbon? A) Carbon dioxide and water B) Carbon monoxide and hydrogen C) Carbon monoxide and water D) Carbon dioxide and hydrogen ____29. What is the systematic name for for Ca(NO3) 2 • 4 H2O ? A) Calcium nitrate dihydrate B) Calcium nitrate tetrahydrate C) Calcium nitrite dehydrate D) Calcium nitrite tetrahydrate ____30. What is the strongest intermolecular force that occurs between Cl2 molecules? A) Dipole forces B) Dispersion forces C) Hydrogen bonding D) Ionic bonding

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PART II – Show your work 1. Perform the following metric-metric conversions (2 pts each): a) 125 cm to mm

b) 255 mg to cg

c) 1.85 mL to µL

d) 8.15 X 104 ms to ks

2. a) A sample of fluorine gas occupies 855 mL at 710 mmHg and 155°C. What is the mass of the sample? (3 pts)

b) A sample of krypton gas has a volume of 500 mL at 225 mmHg and –125°C. What is the pressure in mmHg if the gas occupies 220 mL at 100°C ? (3 pts)

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3. Calculate the heat required to convert 10.0 g of ice at –10.0oC to liquid water at 20.0°C. The specific heat of ice is 0.50 cal/(g°C), the heat of fusion for ice is 80.0 cal/g, and the specific heat of water is 1.00 cal/(g°C). (6 pts)

4. Refer to the periodic table and write the predicted electronic configuration for the following atoms (3 pts each):

a)

P

_________________________________________________

b) Ni

_________________________________________________

5. a) Draw the electron dot structure for the nitrite ion, NO2–. (2 pts)

b) What is the overall, or electron domain, geometry of this molecule? (2 pts) ________________________________

c) What is the molecular geometry of this molecule? (2 pts) ________________________________

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6. a) If 25 moles of butane are combusted according to the following reaction, 2 C4H10 (g) + 13 O2 (g) → 8 CO2 (g) +

10 H2O (g)

how many moles of water will be formed? (2 pts)

b) What is the mass of copper metal that can be prepared from the reaction of 1.25 g of aluminum metal with excess CuSO4 according to the following reaction (4 pts): 2 Al (s) + 3 CuSO4 (aq)



3 Cu (s) + Al2(SO4)3 (aq)

7. Dioxane, a common solvent for plastics, is 54.5 % C, 9.15 % H, and 36.3 % O by mass. a) What is the empirical formula of dioxane? (3 pts)

b) The molar mass of dioxane is 88 g/mol. What is the molecular formula of dioxane? (3 pts)

c) Benzoyl peroxide has the formula C7H6O3 and is the active ingredient in a acne cream. Calculate the percent by mass of carbon in benzoyl peroxide. (2 pts)

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Answers Multiple Choice 1. 6. 11. 16. 21. 26.

D C D A B C

2. 7. 12. 17. 22. 27.

B D D C A C

3. 8. 13. 18. 23. 28.

D A C C D A

4. 9. 14. 19. 24. 29.

B B D D C B

5. 10. 15. 20. 25. 30.

D D A B D B

Show Work 1. a) 1250 mm

b) 25.5 cg

c) 1850 µL

d) 0.0815 ks

2. a) PV = nRT, n = PV / RT = 0.02273 mol of gas (0.02273 mol)(37.9968 g/mol) = 0.864 g of F2 b) P1V1 /T1 = P2V2 / T2, P2 = 1288 mmHg 3. Three steps:

4. a) P b) Ni

1. Heat = (10.0 g)(10.0°C)(0.50 cal/g°C) 2. Heat = (10.0 g)(80.0 cal/g) 3. Heat = (10.0 g)(20.0°C)(1.00 cal/g°C) Total Heat

1s2 2s2 2p6 3s2 3p3

or

[Ne] 3s2 3p3

1s2 2s2 2p6 3s2 3p6 4s2 3d8

5. a)

= 50 cal = 800 cal = 200 cal = 1050 cal

[Ar] 4s2 3d8

or

(two resonance forms; formal charge of one oxygen = –1)

b) Overall geometry = trigonal planar c) Molecular geometry = bent

6. a) 125 mol of H2O b) mol of Al = 0.04633 mol, mol of Cu = 0.06949 mol, grams of Cu = 4.42 g

7. a) Empirical formula = C2H4O

b) Molecular formula = C4H8O2

c) Percent carbon = 60.87 % by mass 8