24. Which elements are most similar in atomic size?
(A) Li (Z = 3) and Na (Z = 11)
(B) B (Z = 5) and Al (Z = 13)
(C) Co (Z = 27) and Rh (Z = 45)
(D) Zr (Z = 40) and Hf (Z = 72)
(E) Be (Z = 4) and F (Z = 9)

20. Which of the following statements is incorrect? (A) The reaction constant might change when the reaction temperature changes. (B) The reaction constant won’t change when the concentration of reactants changes. (C) The reaction constant might change when the catalyst is added to the reaction. (D) The activation of energy for a reaction might change when the catalyst is added. (E) The activation of energy for a reaction might change when the reaction temperature changes.

21. When 6 M sodium hydroxide is added to an unknown white solid, the solid is dissolved. What is a possible identity for this solid? (A) Mg(OH)2 (B) Al2(SO4)3 (C) BaCO3 (D) AgBr (E) Ca3(PO4)2

22. A chemist wishes to separate benzoic acid from 4-hydroxybenzaldehyde. Which is the best method to achieve this separation? (A) Partitioning the mixture between diethyl ether and water. (B) Partitioning the mixture between diethyl ether and 1 M aqueous NaHCO3. (C) Partitioning the mixture between diethyl ether and 1 M aqueous NaOH. (D) Partitioning the mixture between diethyl ether and 1 M aqueous HCl. (E) Recrystallizing the mixture in diethyl ether.

23. The reaction system CO(g) + H2O(g) H2(g) + CO2(g) has already reached equilibrium. Which of the following statements is correct? (A) Additional H2O(g) added to the system will shift to the left to obtain the equilibrium. (B) As an exothermic reaction, the system will shift to the right to attain the equilibrium when temperature increases. (C) When carbon dioxide is removed, the system will shift to the left to achieve the equilibrium. (D) When volume of the reaction container is decreased, the system will shift to the right to reach the equilibrium. (E) Addition of helium gas into the reaction system will have no effects on its equilibrium.

25. In the Lewis structure of I3– , there are _________ electrons around the central iodine atom. (A) 4 (B) 6 (C) 8 (D) 10 (E) 12

26. Which of the following statements is incorrect for colloids? (A) Colloids are suspension of very large particles ( >2000 nm) in a medium. (B) Tyndall effect is observed for colloids. (C) Electric repulsion seems to be the main factor that stabilizes colloids. (D) Removal of soot from smoke is an example of coagulation of colloids. (E) None of the above.

27. Which organic base is NOT found in RNA? (A) Uracil (B) Cytosine (C) Thymine (D) Adenine (E) Guanine

28. The figure below is a cross section of the electron probability distribution for an orbital. What are n and l values for this orbital? (A) n = 3, = 1 (B) n = 2, = 0 (C) n = 2, = 1 (D) n = 3, = 2 (E) n = 2,  = 2

29. A sample of a white solid is known to be NaHCO3, AgNO3, Na2S, or CaBr2. Which 0.1 M aqueous solution can be used to confirm the identity of the solid? (A) NH3(aq) (B) HCl(aq) (C) NaOH(aq) (D) KCl(aq) (E) CH3COOH(aq)

30. The Haber process _____________________ (A) is used to produce nitric acid. (B) is used to produce sulfuric acid. (C) is used to produce ammonia. (D) is used to produce urea. (E) None of the above.