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Unformatted text preview: 188 Chapter Five Gases How do we get there?
N2 H2 What is Charles's law (in aform useful with our knowns)? Vi = V2 r.
What is V2? • V2 T2
=
2.79 L 1
Ar CH4 = (T2)i T Vi = (311 K) 288 K 2.58 L Reality Check: The new volume is greater than the original volume, which makes physical sense because the gas will expand as it is heated.
SEE EXERCISE 5.42 Avogadro's Law
In Chapter 2 we noted that in 1811 the Italian chemist Avogadro postulated that equal volumes of gases at the same temperature and pressure contain the same number of "particles." This observation is called Avogadro's law, which is illustrated by Fig. 5.10. Stated mathematically, Avogadro's law is V= an where V is the volume of the gas, n is the number of moles of gas particles, and a is a proportionality constant. This equation states that for a gas at constant temperature and pressure, the volume is directly proportional to the number of moles of gas. This relationship is obeyed closely by gases at low pressures. 1
Figure 5.10
These balloons each hold 1.0 L gas at 25°C and 1 atm. Each balloon contains 0.041 mol gas, or 2.5 x 1022 molecules. EXAMPLE 5.5 Suppose we have a 12.2L sample containing 0.50 mol oxygen gas (02) at a pressure of 1 atm and a temperature of 25°C. If all this O2 were converted to ozone (03) at the same temperature and pressure, what would be the volume of the ozone? Solution
Where are we going? • To calculate the volume of the ozone produced by 0.50 mol oxygen What do we know? .I ni .I Vi = = 0.50 mol O2 12.2 L O2 .I n2 = ? mol 03 .I V2 = ? L 03 What information do we need? .I Balanced equation
.I Moles of 03 Avogadro's law also can be written as V,
= .I Avogadro's law
V = an V2 n1 n2 How do we get there? How many moles of 03 are produced by 0.50 mol 02? What is the balanced equation? 302(g) + 203(g) ...
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This note was uploaded on 12/13/2010 for the course CHEM 2301 taught by Professor Bill during the Spring '10 term at South Texas College.
 Spring '10
 bill
 Organic chemistry

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