21. The molar mass of a solid as determined by freezing-point depression is 10% higher than the true molar mass. Which of the following experimental errors could not account for this discrepancy?
(A) Before the solution was prepared, the container was rinsed with solvent and not dried.
(B) Some solid was left on the weighing paper.
(C) Not all the solid was dissolved.
(D) The solid dissociated slightly into two particles when it dissolved.
(E) More than the recorded amount of solvents was pipetted into the solution.

17. You analyze for pyridine () by dissolving 0.1000 g of the complex in 100 mL of H2O and titrating with a 0.01 M HCI solution. Which of the following indicators should be used to detect the endpoint? (Assume that the initial concentration of pyridine is approximately 0.01 M.) (A) thymol blue, pH range of color change = 8.0-9.6 (B) methyl red, pH range of color change = 4.8-6.0 (C) bromophenol blue, pH range of color change = 3.0-4.6 (D) bromothymol blue, pH range of color change = 6.0-7.6 (E) alizarin yellow, pH range of color change = 10.1-12.0

18. Which of the following is paramagnetic? (A) (B) (C)(D)(E

19. Which of the following statements about biomolecules is TRUE? (A) Messenger RNA can be found in both the nucleus and the cytoplasm of each cell. (B) Nonpolar groups tend to face the outside of a protein in aqueous solution. (C) Nucleic acids are made of nucleotides joined together with amide bonds. (D) A glycosidic linkage in polysaccharides is an ester group. (E) Table sugar is formed from B-D-glucose and B-D-fructose.

20. Arrange the following species from lowest to highest ionization energy: (A)(B) (C) (D) (E)

22. What is the formula for the compound that crystallizes with a cubic closed packed array of sulfur ions, and that contains zinc ions in 12.5% of the tetrahedral holes and aluminum ions in 50% of the octahedral holes? (A) ZnAISA (B) ZnA12S4 (C) ZnAlS2 (D) ZnAl2S2 (E) ZnAl4S8

23. Metal X has a body-centered cubic structure. If the atomic radius of X is R, what is the edge length of the unit cell? (A)2R (B)√2R (C) (D) (E) √3 R

24. Samples of the gases H2(g) and SO2(g) have equal masses and are at the same temperature and pressure. Calculate the ratio of rates of impact with the walls (H2:SO2). (A) 180 (B) 32 (C) 5.6 (D) 1.0

25. Consider the following gas samples:Which of the following statements is NOT TRUE?(A) Assuming identical intermolecular forces in the two samples, sample M should be morenearly ideal than sample N.(B) The root-mean-square velocity of molecules in sample M is twice as large as the root-mean-square velocity of molecules in sample N.(C) The average kinetic energy of the molecules in sample M is twice the average kineticenergy of the molecules in sample N.(D) The fraction of molecules in sample M having kinetic energies greater than some highfixed value is larger than the fraction of molecules in sample N having kinetic energiesgreater than that same high fixed value.(E) The volume of sample M is twice the volume of sample N.

26. A 0.100 g sample of the weak acid HA (molar mass = 100 g/mol) is dissolved in 500 g water. The freezing point of the resulting solution is -0.0056 *C. Calculate the value of Ka for this acid. Assume molarity equals molality in this solution. (The molal freezing point depression constant Kris 1.86 ℃) (A)(B)(C)(D)(E)

27. Two isomers (A and B) of a given compound dimerize as follows:Both processes are known to be second order in the reactant, and ki is known to be . In a particular experiment A, and B were placed in separate container at 25 ℃,where and . After each reaction had progressed for 3.00 min, [A] = 3.00 [B]. In this case the rate laws are define as follows:The concentration of A2 after 3.00 min is x M. The half-life for the experiment involving B isy s. What are the values of x and y?(A)(B)(C) (D)(E)