26.07.2021 Views

General Chemistry Principles, Patterns, and Applications, 2011

General Chemistry Principles, Patterns, and Applications, 2011

General Chemistry Principles, Patterns, and Applications, 2011

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

density, 58 g/L. The major constituent of the atmosphere (>95%) is carbon. Calculate the molar mass of<br />

the major gas present <strong>and</strong> identify it.<br />

Answer: 44 g/mol; CO 2<br />

Summary<br />

The empirical relationships among the volume, the temperature, the pressure, <strong>and</strong> the amount of a gas<br />

can be combined into the ideal gas law, PV = nRT. The proportionality constant, R, is called the gas<br />

constant <strong>and</strong> has the value 0.08206 (L·atm)/(K·mol), 8.3145 J/(K·mol), or 1.9872 cal/(K·mol),<br />

depending on the units used. The ideal gas law describes the behavior of an ideal gas, a hypothetical<br />

substance whose behavior can be explained quantitatively by the ideal gas law <strong>and</strong> the kinetic molecular<br />

theory of gases. St<strong>and</strong>ard temperature <strong>and</strong> pressure (STP) is 0°C <strong>and</strong> 1 atm. The volume of 1 mol of<br />

an ideal gas at STP is 22.41 L, thest<strong>and</strong>ard molar volume. All of the empirical gas relationships are<br />

special cases of the ideal gas law in which two of the four parameters are held constant. The ideal gas law<br />

allows us to calculate the value of the fourth quantity (P, V, T, or n) needed to describe a gaseous sample<br />

when the others are known <strong>and</strong> also predict the value of these quantities following a change in conditions<br />

if the original conditions (values of P, V, T, <strong>and</strong> n) are known. The ideal gas law can also be used to<br />

calculate the density of a gas if its molar mass is known or, conversely, the molar mass of an unknown gas<br />

sample if its density is measured.<br />

K E Y T A K E A W A Y<br />

<br />

The ideal gas law is derived from empirical relationships among the pressure, the<br />

volume, the temperature, <strong>and</strong> the number of moles of a gas; it can be used to calculate<br />

any of the four properties if the other three are known.<br />

K E Y E QU A T I ON S<br />

Ideal gas law<br />

Equation 10.12: PV = nRT<br />

Relationship between initial <strong>and</strong> final conditions<br />

Equation 10.19 : P1V1T1= P2V2T 2 n is constant<br />

Density of a gas<br />

Equation 10.23: d = PMRT C O N C E PTUAL P R OBLEMS<br />

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

Saylor.org<br />

916

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!