18. Most valence electron transitions occur in the _ region of the electromagnetic spectrum. Rotational transitions are typically induced by radiation in the region, and vibrational transitions are typically induced by radiation in the _ region. (A) X-ray, UV-vis, IR (B) UV-vis, IR, microwave (C) IR, microwave, UV-vis (D) Microwave, X-ray, UV-vis (E) UV-vis, microwave, IR

28. Which of the following statements about ideal gases and real gases are correct? (A) The assumptions of the ideal-gas model include negligible molecular volume and the absence of intermolecular forces. (B) The molar volume of an ideal gas is about 22.4 L/mol at standard temperature and pressure (STP), where STP corresponds to 1 atm and 25°C. (C) For a fixed amount of gas in a rigid container, the pressure approximately doubles when the temperature increases from 100°C to 200°C. (D) Neon behaves more ideally than ammonia under the same conditions. (E) The lower the pressure and the lower the temperature, the more closely a real gas approaches ideal-gas behavior.

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