4. Consider the reaction: a X(g) = b Y(g)

Each entry in the table below represents the equilibrium partial pressures of X and Y under different initial conditions at the same temperature. The coefficients a and b are the simplest integers. When the equilibrium partial pressure of X is 0.20 atm, the equilibrium partial pressure of Y is n atm. Which of the following statements is true?

(A) a = 1
(B) b = 2
(C) n = 0.10
(D) a = 2b
(E) a + b = 4

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1. Consider a system consisting of the following apparatus, in which gas is confined in flask A and there is a vacuum in flask B. The flasks are separated by a valve. A B Assuming that the flasks are perfectly insulated and will not allow the flow of heat into or out of the flasks to the surroundings. When the valve is opened, gas flows from flask A to flask B. Which of the following5 atm Evacuated statements regarding this process is correct? (A) No work is performed during the expansion of the gas. (B) The gas expansion is a nonspontaneous process. (C) The driving force for this process is enthalpy change. (D) The internal energy change (ΔΕ) for this expansion process is ＞ 0. (E) The entropy change of the surrounding (ASsurr) for this process is ＞ 0.

2. Given the values for the following compounds: Which of the following statements about these compounds is   incorrect  ? (A) The solubility of MnS in water is pH dependent. (B) Zn(OH)2 has the lowest molar solubility in water. (C) Pb(OH)2 has the highest molar solubility in water. (D) Zn(OH)2 is more soluble upon decreasing the pH of solution. (E) A saturated PbCrO4 solution has a lower than a saturated Pb(OH)2 solution.

3. An unknown compound X was found to have molecular peak of m/z = 74 by mass spectrometry and a measured boiling point of 57°C at latm. Which of the following is most likely to be compound X? (A) diethyl ether (D) butanone (B) methyl acetate (E) n-pentane (C) propionic acid

5. Which of the following amino acids has the correct ionized form for the functional groups at physiological pH (7.4)? (A)(B)(C)(D) (E)

6. Which of the following statements about electrochemical cells is incorrect? (A) The standard potential （E°）in a concentration cell is zero. (B) In a concentration cell, the higher ion concentration solution is present at the cathode. (C) At equilibrium, the standard potential （E°） in a cell is zero. (D) The cell potential （E）can determine the spontaneity of a cell. (E) In a concentration cell, decreasing the anode ion concentration will give rise to larger cell potentials.

7. Which of the following names for compounds complies to IUPAC nomenclature? (A) 2,5-pentadiene (B) cis-1-butene (D) trans-1,1-dichlorocyclohexane (C) (R)-bromocyclopentane (E) propanal

8. Which of the following molecules does not belong to 20 common amino acids? (A)(B)(C)(D)(E)

9. In preparation for the combustion demonstration, the assistant instructor injected equal molar amount of H2 and O2 into the balloon, but the demonstration had to be postponed until the next day due to safety setup problems. During the night, both gases leaked through the pores of the balloon. What is the molar ratio of O2 to H2 in the balloon the next day if 30% of the H2 is leaking? (A) 0.76 (B) 0.95 (C) 1.14 (D) 1.32 (E) 1.60

10. The following statements describe the chemical and physical properties of some representative elements and their compounds. Which statement is   incorrect  ? (A) Diborane (B2H6) has two three-center two-electron B-H-B bonds. (B) Lithium metal is converted to lithium superoxide in the presence of excess molecular oxygen. (C) Al2O3 is amphoteric and can dissolve in both acidic and basic solutions. (D) The hydration of F¯ decreases the entropy when HF dissociates in water, which contributes to make HF a weaker acid than HCl and HBr. (E) SiC is an extremely hard substance because it has a covalent network structure similar to diamond.