1. 2.80 grams of a monoprotic weak acid, HX, was dissolved in water. Titration of the acid to its equivalence point required 29.2 mL of 0.500 M NaOH solution. What is the molecular weight of the acid, HX?

(A) 192 g/mol
(B) 164 g/mol
(C) 96.0 g/mol
(D) 5.21 g/mol

2. The ionic reaction

3 I¯ + S₂O₈²¯ ---> 2 SO₄²¯ + I₃¯

is found to be described by the experimental rate equation

rate = k[I¯] [S₂O₈²¯]

This suggests that

(A) the reaction occurs when three iodide ions collide simultaneous with one S₂O₈²¯ ion
(B) there must be only one step in the overall reaction since the rate is first-order in both reactants
(C) the rate of reaction is inhibited by the presence of I₃¯
(D) a slow step in the overall reaction sequence may involve the collision of a single I¯ ion with a single S₂O₈²¯ ion

3. The hemoglobin from the red corpuscles of most mammals contains approximately 0.33% iron by weight. If physical measurements indicate a molecular weight for hemoglobin of 68000 g/mol, how many iron atoms are there in each molecule of hemoglobin? (AW Fe= 56)

(A) 1
(B) 2
(C) 3
(D) 4

4. Given the following standard enthalpies of formation in kJ/mol:

CO₂ -393.3, CH₃OH -238.5, H₂O -285.3.

What is the heat of combustion of methanol, CH₃OH, in kJ/mol?

(A) -725.4
(B) -154.8
(C) -140.8
(D) 154.8

5. An element whose neutral atoms would be expected to be paramagnetic is

(A) neon
(B) fluorine
(C) magnesium
(D) zinc

6. The heat of formation of gaseous water molecules is -241.8 kJ/mol. If the H-O bond energy is 463 kJ/mol and the H-H bond energy is 435 kJ/mol, what is the energy of the bond between oxygen atoms in the O₂ molecule in kJ/mol?

(A) 0
(B) 249
(C) 428
(D) 498

7. The osmotic pressure of an aqueous solution containing 30.0 g of a newly-isolated protein in one liter of solution is 12.7 torr at 25 °C. What is the approximate molecular weight of the protein in g/mol?

(A) 58
(B) 333
(C) 4000
(D) 44000

8. Carbon dioxide is a gas at room temperature while silicon dioxide is a high-melting solid. The best explanation of this difference is that

(A) Si has more electrons than C
(B) the atoms in CO₂ are bound by covalent bonds while SiO₂ is an ionic compound
(C) van der Waals' forces are stronger in SiO₂
(D) CO₂ consists of discrete molecules while in SiO₂ atoms are joined by a network of covalent bonds

9. 2.00 moles of NO and an undetermined amount of O₂ are placed in a one-liter container at 460 °C. When the reaction

2 NO(g) + O₂(g) <===> 2 NO₂(g)

reaches equilibrium, we find 0.00156 mol of O₂ and 0.500 mol of NO₂. The value of the equilibrium constant for this system is

(A) 4.42
(B) 40.1
(C) 71.2
(D) 214

10. Proteins are macromolecules in which the simplest repeating structural units are

(A) nucleic acids
(B) amino acids
(C) purines
(D) carbohydrates

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