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CHEMISTRY 1AFALL 2006 EXAM 1 KEY

CH. 1-3

YOU MIGHT FIND THE FOLLOWING USEFUL;

Electronegativities

H2.2

Li Be B C N O F0.98 1.57 2.04 2.55 3.04 3.44 3.98

Na Mg Al Si P S Cl0.93 1.31 1.61 1.9 2.19 2.58 3.16

K Ca Ga Ge As Se Br0.82 1.0 1.81 2.01 2.18 2.55 2.96

Rb Sr In Sn Sb Te I Xe0.82 0.95 1.78 1.96 2.05 2.1 2.66 2.6

Cs Ba Tl Pb Bi Po0.79 0.89 2.33 2.02 2.0 2.2

Answer the following by writing the word, words, letter, letters or number in each blankthat best completes each sentence. (2 points each blank)

1. A(n) element is a substance that cannot be chemically converted into simpler substances; a

substance in which all of the atoms have the same number of protons and therefore the

same chemical characteristics.

2. The name of the group on the periodic table in which potassium, K, is found isalkalimetal. Its group number is1 or 1A. Potassium is in the4th period. It is arepresentative

(or main-group) element (representative element, transition metal or inner transition

metal).

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3. An ion formed from an atom that has gained one or more electrons and thus has become

negatively charged is called a(n)anion .

4. The N-H bond is a(n) polar covalent (ionic, polar covalent, or nonpolar covalent) bond.

5.

In the F-H polar covalent bond, theF atom has the partial negative charge.6. Hydrocarbons are compounds that contain only carbon and hydrogen.

7. A(n) oxyanion is a polyatomic ion with the general formula Ha XbOcd-. (The a can be 0.)

8. A(n) formula unit is a group represented by a substance’s chemical formula, that is, a group

containing the kinds and numbers of atoms or ions listed in the chemical formula. It is a

general term that can be used in reference to elements, molecular compounds, or ionic

compounds.

9. Draw a reasonable Lewis structure for C2F2. (6 points)

10. Identify each of the following as a binary covalent compound, a binary ionic compound, abinary acid, an ionic compound with a polyatomic ion, an oxyacid, an alcohol, or a sugar. Write name for each. (10 points)

Chemical Formula Type of Substance Name

C4H10 binary covalent butane

Fe(HCO3)2 ionic with polyatomic ion Iron(II) hydrogen carbonate

H3PO2 oxyacid hypophosphorous acid

Cr2(SO3)3 ionic with polyatomic ion chromium(III) sulfite

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11. Identify each of the following as a binary covalent compound, a binary ionic compound, abinary acid, an ionic compound with a polyatomic ion, an oxyacid, an alcohol, or a sugar. Write formula for each. (10 points)

Chemical Formula Type of Substance Formula

hydrofluoric acid binary acid HF(aq)

2-propanol alcohol C3H 7OHor

CH 3CH(OH)CH 3

zinc phosphate ionic with polyatomic ion Zn 3(PO 4)2

hydrogen iodide binary covalent HI

12. Complete the following table by (1) writing the name for the type of particle viewed as

forming the structure of a solid, liquid, or gas of each of the following substances and (2) writing the name of the type of attraction holding these particles in the solid and liquidform, e.g. covalent bonds, dipole-dipole attractions, etc. (1 point each box)

Substance Particles to Visualize Type of Attraction

phosphorus molecules London forces

C8H18 molecules London forces

helium atoms London forces

C2H5OH molecules hydrogen bonds

NH 4OH cations and anions ionic bonds

hydrogen chloride molecules dipole-dipole attraction

Mn cations in sea of e- metallic bonds

13. Draw the Lewis structure for 2-methylbutane. (4 points)

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Set up the following numerical problems. Be sure to carefully show your work. NOTE: Remember that problem. Even if you cannot do all of a problem, be sure to set up as much of it as you can. (8 points each

14. Hydrochloric acid, HCl(aq), that is 29% by mass HCl (71% water) is used to remove metal oxides

or for the addition of a chrome covering. How many megagrams of this hydrochloric acid solution1.6 x 108 kg of pure HCl?

⎛ ⎞ ⎛ ⎞ ⎛ ⎞⎜ ⎟ ⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠ ⎝ ⎠

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100 kg soln 10 g 1Mg? Mg soln =1.6 x 10 kg HCl

29 kg HCl 1kg 10 g = 5.5 105 Mg soln

15. Manganese metal is produced from the manganese(III) oxide, Mn2O3, which is found in manganite, a manmanganese are in 1.261 tons of Mn2O3? (1 ton = 2000 lb)

2 32 3

2 3 2 3

1mol Mn O2000 lb 453.6 g 2 mol Mn 54.9380 g Mn 1lb? lb Mn =1.261ton Mn O1ton 1lb 157.874 g Mn O 1mol Mn O 1mol Mn 453.6 g

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= 1755 lb Mn

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Answer the following in short answer form.

16. Answer the following questions that relate to the process of the formation of solid sodiumchloride from solid sodium and gaseous chlorine. (4 points each part)

a. Describe the general structure of metallic elements, such as sodium.

b. Describe the structure of gaseous chlorine. Your description should include aspecific description of the particles that form chlorine’s structure and a generaldescription of the structure of gases.

Chlorine gas is composed of diatomic molecules, Cl 2 , which contain two tiny nuclei,each with a +17 charge generated by the 17 protons in each nucleus. These nuclei are surrounded by a− 34 charge cloud generated by the 34 electrons, 17 from each atom. As a gas, the particles occupy a very small fraction of the total volume (typically about 0.1%). The average distance between particles of a typical gas is about tentimes their diameter. Because of this significant distance between them, there areessentially no attractions or repulsions between particles. The particles move in straight-line paths, colliding constantly with other particles and changing their

direction and velocity.

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c. Describe the process that leads to the formation of the ionic bond between sodiumand chlorine atoms in sodium chloride.

Cl 2 molecules collide with sodium atoms on the surface of the solid sodium, and a

tug-of-war arises between chlorine atoms and sodium atoms for electrons. The

chlorine atoms attract electrons more strongly, so one electron is transferred fromeach sodium atom to each chlorine atom, forming sodium cations, Na+ , andchloride anions, Cl − .

d. Write a description of the sodium chloride crystal structure.