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General Chemistry Principles, Patterns, and Applications, 2011

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9. Air consists primarily of O 2 , N 2 , Ar, Ne, Kr, <strong>and</strong> Xe. Use the concepts discussed in this chapter to propose two<br />

methods by which air can be separated into its components. Which component of air will be isolated first?<br />

10. How can gas liquefaction facilitate the storage <strong>and</strong> transport of fossil fuels? What are potential drawbacks to<br />

these methods?<br />

N U M E R I C A L PR O BL E M S<br />

1. The van der Waals constants for xenon are a = 4.19 (L 2·atm)/mol 2 <strong>and</strong> b = 0.0510 L/mol. If a 0.250 mol sample<br />

of xenon in a container with a volume of 3.65 L is cooled to −90°C, what is the pressure of the sample<br />

assuming ideal gas behavior? What would be theactual pressure under these conditions?<br />

2. The van der Waals constants for water vapor are a = 5.46 (L 2·atm)/mol 2 <strong>and</strong> b = 0.0305 L/mol. If a 20.0 g<br />

sample of water in a container with a volume of 5.0 L is heated to 120°C, what is the pressure of the sample<br />

assuming ideal gas behavior? What would be the actual pressure under these conditions?<br />

10.9 Essential Skills 5<br />

T O PI C S<br />

<br />

<br />

Preparing a Graph<br />

Interpreting a Graph<br />

Previous Essential Skills sections presented the fundamental mathematical operations you need to know to solve<br />

problems by manipulating chemical equations. This section describes how to prepare <strong>and</strong> interpret graphs, two<br />

additional skills that chemistry students must have to underst<strong>and</strong> concepts <strong>and</strong> solve problems.<br />

Preparing a Graph<br />

A graph is a pictorial representation of a mathematical relationship. It is an extremely effective tool for<br />

underst<strong>and</strong>ing <strong>and</strong> communicating the relationship between two or more variables. Each axis is labeled<br />

with the name of the variable to which it corresponds, along with the unit in which the variable is<br />

measured, <strong>and</strong> each axis is divided by tic marks or grid lines into segments that represent those units (or<br />

multiples). The scale of the divisions should be chosen so that the plotted points are distributed across the<br />

entire graph. Whenever possible, data points should be combined with a bar that intersects the data point<br />

<strong>and</strong> indicates the range of error of the measurement, although for simplicity the bars are frequently<br />

omitted in undergraduate textbooks. Lines or curves that represent theoretical or computational results<br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

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