CHM 101 NAME ______

GAGE

FALL 2007 DATE ______

EXAM 2

I. Select the best response for each of the following questions or statements. (24)

_____ 1. Cold packs, whose temperatures are lowered when ammonium nitrate dissolves in water, are carried by athletic trainers when transporting ice is not possible. Which of the following is true of this reaction?
A. DH < 0, process is exothermic

B. DH > 0, process is exothermic

C. DH < 0, process is endothermic

D. DH > 0, process is endothermic

E. DH = 0, since cold packs are sealed

_____ 2. Natural gas, or methane, is an important fuel. Combustion of one mole of methane releases 802.3 kilojoules of energy. How much energy does that represent in kilocalories?
A. 1.92 ´ 10-1 kcal D. 1.92 ´ 105 kcal

B. 1.92 ´ 102 kcal E. 3.36 ´ 106 kcal

C. 3.36 ´ 103 kcal

______3. Which scientist first proposed that the electron in the hydrogen atom can have only certain energies?

A. Planck D. Rydberg

B. Einstein E. Heisenberg

C. Bohr

_____ 4. Select the arrangement of electromagnetic radiation which starts with the lowest energy and increases to greatest energy.

A. radio, infrared, ultraviolet, gamma rays

B. radio, ultraviolet, infrared, gamma rays

C. gamma rays, infrared, radio, ultraviolet

D. gamma rays, ultraviolet, infrared, radio

E. infrared, ultraviolet, radio, gamma rays

_____ 5. Select the correct electron configuration for Te (Z = 52).

A. [Kr]5s25p64d8 D. [Kr]5s24f14

B. [Kr]5s25d105p4 E. [Kr]5s24d105p4

C. [Kr]5s24d105p6

_____ 6. Elements with the highest first ionization energies are found in the ______region of the periodic table.

A. lower left D. lower right

B. upper left E. upper right

C. center

_____ 7. Elements with ______first ionization energies and ______electron affinities generally form cations.

A. low, very negative

B. high, positive or slightly negative

C. low, positive or slightly negative

D. high, very negative

E. None of these is generally correct.

_____ 8. What is the correct order of decreasing size of the following ions?

A. P3- > Cl- > K+ > Ca2+ D. K+ > Cl- > P3- > Ca2+

B. Ca2+ > K+ > Cl- > P3- E. None of these is correct.

C. K+ > Cl- > Ca2+ > P3-

_____ 9. In which of these substances are the atoms held together by polar covalent bonding?

A. SrCl2 D. TiF2

B. CsCl E. S8

C. ClF

_____ 10. Electronegativity is a measure of

A. the energy needed to remove an electron from an atom.

B. the energy released when an electron is added to an atom.

C. the magnitude of the negative charge on an electron.

D. the attraction by an atom for electrons in a chemical bond.

E. the magnitude of the negative charge on a molecule.

_____ 11. Arrange oxygen, sulfur, calcium, rubidium and potassium in order of decreasing atomic radius.

A. O > S > Ca > K > Rb

B. O > S > Ca > Rb > K

C. O > S > Rb > K > Ca

D. O > S > Rb > Ca > K

E. None of these orders is correct.

_____ 12. Based on electronegativity trends in the periodic table, predict which of the following compounds will have the greatest % ionic character in its bonds.

A. H2O D. RbF

B. LiI E. HCl

C. CaO

II. Select the best response for each of the following questions or statements. (16)

_____ 1. Calculate the number of moles in 17.8 g of the antacid magnesium hydroxide.

A. 3.28 mol D. 0.305 mol

B. 2.32 mol E. 0.200 mol

C. 0.431 mol

_____ 2. Calculate the number of oxygen atoms in 29.34 g of sodium sulfate, Na2SO4.

A. 1.244 ´ 1023 O atoms D. 2.915 ´ 1024 O atoms

B. 4.976 ´ 1023 O atoms E. 1.166 ´ 1025 O atoms

C. 2.409 ´ 1024 O atoms

_____ 3. The highly exothermic thermite reaction, in which aluminum reduces iron(III) oxide to elemental iron, has been used by railroad repair crews to weld rails together.

2Al(s) + Fe2O3(s) ® 2Fe(s) + Al2O3(s) / DH = -850 kJ

What mass of iron is formed when 725 kJ of heat are released?

A. 47 g D. 112 g

B. 65 g E. 130 g

C. 95 g

_____ 4. The FM station KDUL broadcasts music at 99.1 MHz. Find the wavelength of these waves.

A. 1.88 ´ 10-2 m D. 5.33 ´ 102 m

B. 0.330 m E. > 103 m

C. 3.03 m


SHOW ALL WORK TO RECEIVE CREDIT FOR PROBLEMS.

III.  Use the equation below to solve the problems below.

3 LiC2H3O2 + AlCl3 à 3 LiCl + Al(C2H3O2)3

a.  How many grams of lithium chloride can be formed when you react 25.0 grams of lithium acetate with 20.0 g of aluminum chloride? (12)


b. If you actually produce 13.6 grams of lithium chloride, what is your % yield? (5)

c. A compound is analyzed and found to contain 6.0% lithium, 45.3% chromium, and 48.2% oxygen. Determine the empirical formula. (10)

IV.  Use the graph above to answer the questions below.

a.  Determine the ΔH for the reaction. ______(5)

b.  Is the reaction endothermic or exothermic? Explain your choice. (3)

c. On the axes above, sketch what the graph would look like for this reaction if you added a catalyst at the start of the reaction. (2)

V.  a. Complete the table below with the Lewis dot structure and structural formula with each bond dipole shown on the structural formula. (15)

Substance / Lewis dot structure / Structural formula with bond dipole moments
CHFCHF
PO33-
SCl3H3

b. Oxygen can form either covalent or ionic bonds. Explain the nature of each bond, the conditions under which each forms and the type of substances in each bond. (8)

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