21. Compare the following molecules, what is the order of decreasing bond order?
1. 2. N₂ 3.
(A) 1=2=3
(B) 3＞2＞1
(C) 1＞2＞3
(D) 2＞1=3
(E) 1=3＞2

17. Which of the following statements is correct?f. An excited atom can return to its ground state by emitting electromagnetic radiation.ff. The energy of an atom is increased when electromagnetic radiation is emitted from it.fff. The energy of electromagnetic radiation increases as its frequency increases.fV. An electron in the n=4 state in the hydrogen atom can go to the n=2 state by emittingelectromagnetic radiation at the appropriate frequency.V. The frequency and wavelength of electromagnetic radiation are inversely proportional toeach other.(A) f, fff, fV, V (B) fff, V (C) f, ff, fff (D) fff, fV, V (E) f, ff, fV

18. Given values of the following acids:What is the order of increasing base strength?(A)(B)(C) (D)(E)

19. The molecular formula of the ion is , where X is an element from Group 6A. What is the hybridization of X atom?(A) sp (B) sp2 (C) sp3 (D) dsp3 (E) d2sp3

20. Which ion has the largest ionic size among the following?(A) (B) (C) (D) (E)

22. Which of the following statements is correct?(A) BF₃ has 24 total valence electrons, is an exception to the octet rule, and has resonance.(B) BF₃ has 24 total valence electrons, is an exception to the octet rule, and does not haveresonance.(C) BF₃ has 24 total valence electrons, obeys the octet rule, and has resonance.(D) BF₃ has 22 total valence electrons, is an exception to the octet rule, and does not haveresonance.(E) BF₃ has 24 total valence electrons, obeys the octet rule, and does not have resonance.

23. Which chemical process gives beer its brown color?(A) Maillard reaction (B) Caramelization (C) Oxidation of ethanol(D) Hydrolysis of starch (E) All of above

24. Arrange the following bonds in order of decreasing polarity:1. H-H 2. C-F 3. Al-F 4. N-O(A) 1＞2＞3＞4 (B) 3＞2＞4＞1 (C) 1＞3＞2＞4(D) 1＞4＞2＞3 (E) 3＞4＞2＞1

25. The density of a gas is 2 g/L at 3 atm and 27oC. What is the molar mass of the gas (g/mol)?(A) 1.48 (B) 32 (C) 149.6 (D) 9.3 (E) 16.4

26. Which of the following reactions does not involve oxidation-reduction?(A) CH4 + 3O2→ 2H2O + CO2 (B) PCl3 + Cl2 →PCl5(C) 2Na + 2H2O →2NaOH + H2 (D) MnO2 + 4HCl→ Cl2 + 2H2O + MnCl2(E) CO2 + 2LiOH →Li2CO3 + H2O

27. Calculate the standard change in enthalpy for the reaction and select the correct answer: (A) exothermic reaction(B) endothermic reaction(C) no energy change for this reaction(D) Lack of makes calculation impossible.(E) None of the above.