Chapter 11
Gases
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t’s Monday morning, and Lilia is walking out of the chemistry building, thinking about the introductory lecture on gases that her instructor just presented. Dr. Scanlon challenged the class to try to visualize gases in terms of the model she described, so Lilia looks at her hand and tries to picture the particles in the air bombarding her skin at a rate of 1023 collisions per second. Lilia has high hopes that a week of studying gases will provide her with answers to the questions her older brothers and sisters posed to her the night before at a family dinner.
When Ted, who is a mechanic for a Formula One racing team, learned that Lilia was going to be studying gases in her chemistry class, he asked her to find out how to calculate gas density. He knows that when the density of the air changes, he needs to adjust the car’s brakes and other components to improve its safety and performance. John, who is an environmental scientist, wanted to be reminded why balloons that carry his scientific instruments into the upper atmosphere expand as they rise. Amelia is an artist who recently began to add neon lights to her work. After bending the tubes into the desired shape, she fills them with gas from a high pressure cylinder. She wanted to know how to determine the number of tubes she can fill with one cylinder.
Lilia’s sister Rebecca, the oldest, is a chemical engineer who could answer Ted’s, John’s, and Amelia’s questions, but to give Lilia an opportunity to use her new knowledge, she keeps quiet except to describe a gas-related issue of her own. Rebecca is helping to design an apparatus in which two gases will react at high temperature, and her responsibility is to equip the reaction vessel with a valve that will keep the pressure from rising to dangerous levels. She started to explain to Lilia why increased temperature leads to increased pressure, but when Lilia asked what gas pressure was and what caused it, Rebecca realized that she had better save her explanation for the next family dinner. Lilia (like yourself) will learn about gas pressures and many other gas related topics by reading Chapter 11 of her textbook carefully and listening closely in lecture.
11.1 Gases and Their Properties
11.2 Ideal Gas Calculations
11.3 Equation Stoichiometry and Ideal Gases
11.4 Dalton’s Law of Partial Pressures
Convert between temperatures in the Celsius and Kelvin scales. (Section 2.6)
Describe the particle nature of gases. (Section 3.1)
Convert the amount of one substance in a given reaction to the amount of another substance in the same reaction, whether the amounts are described by mass of pure
substance or volume of a solution containing a given molarity of one of the substances. (Sections 10.1 and 10.3)
Given an actual yield and a theoretical yield for a chemical reaction (or enough information to calculate a theoretical yield), calculate the percent yield for the reaction. (Section 10.2)
Review Skills
The presentation of information in this chapter assumes that you can already perform the tasks listed below. You can test your readiness to proceed by answering the Review Questions at the end of the chapter. This might also be a good time to read the Chapter Objectives, which precede the Review Questions.
The gas particles in the air around us are constantly colliding with our skin.
