21. The molar ratio of Cl⁻, Br⁻, and I in a solution is 2:3:4. Now, if you want to pass Cl₂ into the solution so that the molar ratio of Cl⁻, Br⁻, and I in the solution becomes 4:3:2, what is the molar ratio of Cl₂ to be added and I in the original solution?
(A) 1:2
(B) 1:3
(C) 1:4
(D) 1:5
(E) 1:6

17. Which of the following compounds (A-E) is not aromatic?  (A) A (B) B (C) C (D) D (E) E

18. Titrating 30.00 mL of a saturated calcium iodate solution requires 27.00 mL of a 0.100 M solution of Na₂S₂O₃ according to the equation IO₃⁻ + S₂O₃²⁻ + H⁺ → I⁻ + S₄O₆²⁻ + H₂O (not balanced) What is the Ksp for Ca(IO₃)₂? (A) 7.14 × 10⁻⁸ (B) 1.68 × 10⁻⁶ (D) 4.62 × 10⁻⁴ (E) 6.23 × 10⁻² (C) 2.79 × 10⁻⁵

19. In an organic solution, an organometallic compound R3MPH3 (R = alkyl, M = metal) decomposes into a hydrocarbon R-R and a new compound RMPH3. The mechanism for the reaction was proposed as follows. The first and third steps are fast, whereas the second step is slow. What is the rate law based on the mechanism? (A) Rate =(k1k3/k-1)R3MPH3[PH3] (B) Rate = R-R/[R3M] (C) Rate = (k2k1/k-1)[R3MPH3]/[PH3] (D) Rate = k2[R3M]/[PH3] (E) Rate = k1[R3MPH3]

20. The heat required to raise the temperature from 298 K to 398 K for 2 moles of a gas at constant volume is 4155 J. At constant pressure, the internal energy required to heat the same gas from 450 K to 550 K is 4960 J, and the gas does 857 J of work during this expansion. Which of the following statements is correct? (R = 8.31 J mol⁻¹ K⁻¹) (A) This gas is monatomic. (B) This gas is not an ideal gas. (C) The molar heat capacity at constant volume is 41.55 J mol⁻¹ K⁻1. (D) The molar heat capacity at constant pressure is 49.60 J mol⁻¹ K⁻1. (E) The internal energy change is 2078 J when the gas is heated from 273 K to323 K at constant pressure

22. Methane monooxygenase (s-MMO) contains a dinuclear iron active center and is a catalyst for the oxidation of CH4 by O2 to form CH3OH; the reaction process is shown below. Which of the following statements is incorrect? (A) Theelectronic configuration of the ground state Fe atom is [Ar]3d64s². involves the breaking of a non-polar bond and the formation of (B) Step polar bonds. (C) Electron transfer occurs between iron and oxygen atoms in each step. (D) Radical species are produced during the reaction. (E) The overall reaction shown is CH4 + O2 + 2H⁺ +2 CH3OH+ H2O

23. Which pair of the following compounds that measured under the same conditions have the same amplitude of specific rotation but with opposite direction? (A) cis-1,2-dichlorocyclopentane and trans-1,2-dichlorocyclopentane (B) (2S, 3R)-butane-2,3-diol and (2R, 3S)-butane-2,3-diol (C) cis-2-butene and trans-2-butene (D) (2S, 3R)-butane-2,3-diol and (2R, 3R)-butane-2,3-diol (E) D-glucose and L-glucose

24. (i) The number of the following species which exhibit resonance is a. O3, SeO2, NF3, N2O, CCl4, SCN⁻, OF2 (ii) The number of the following diatomic species which are paramagnetic is b.  What is (a + b)? (A) 5 (B) 6 (C) 7 (D) 8 (E) 9

25. 2-Methoxy-2-methylbutane (TAME) is commonly used as a gasoline additive. With the presence of appropriate catalysts, TAME can be produced by the liquid- liquid reaction between methanol and olefins, in which the following reactions occur simultaneously. The equilibrium constants Kx, expressed in terms of the amount fraction of the substance, for reactions I, II, and III are shown above. What is the range of values of ?  (A) ＜-1 (B)-1~0 (C) 0~1 (D) ＞ 1  (E)

26. Consider the reaction 2 X(g) + Y(g) ⇌2Z(g) in a rigid container at 27 °C. The initial concentrations of X and Y are 2.0 mol/L and 3.0 mol/L, and 1.0 mol/L of Z will be produced at equilibrium. If you want to prepare 0.40 atm of Z from an initial pressure of 1.0 atm of X, what would be the approximate initial pressure of Y? (gas constant R = 0.082 atm·L·K⁻¹·mol⁻¹) (A) 1.3 atm (B) 3.3 atm (C) 10.2 atm (D) 21.3 atm (E) 28.0 atm

27. The formation of stalactite is closely related to the concentration of carbon- containing species formed by the dissolution of CaCO3 in the rocks and CO2 in the air in natural water bodies. Given that (CaCO3) = , pM = -log[M] where M = , the variation of pM with pH  in a cave water body at room temperature is shown on the right.  Which of the following is   incorrect  ?  (A) represents . (B) (C) m = 2.75 and n = 4.35 (D) When pH is 10.3, (E) When pH is increased from 4 to 8, increases faster than .