Jump to a New ChapterIntroduction to the SAT IIIntroduction to the SAT II Chemistry TestStrategies for Taking the SAT II Chemistry TestThe Structure of MatterThe States of MatterReaction TypesStoichiometryEquilibrium and Reaction RatesThermodynamicsDescriptive ChemistryLaboratoryBasic Measurement and Calculation ReviewChemical Formulas Review: Nomenclature and Formula WritingPractice Tests Are Your Best Friends
 5.1 Intra- and Intermolecular Forces 5.2 Solids 5.3 Liquids 5.4 Gases 5.5 Phase Changes 5.6 The Gas Laws 5.7 Boyle’s Law 5.8 Charles’s Law

 5.9 Avogadro’s Law 5.10 The Ideal Gas Law 5.11 Density of Gases 5.12 Dalton’s Law of Partial Pressures 5.13 Graham’s Law of Diffusion and Effusion 5.14 Solutions 5.15 Practice Questions 5.16 Explanations
The Ideal Gas Law
The ideal gas law is the most important gas law for you to know: it combines all of the laws you learned about in this chapter thus far, under a set of standard conditions. The four conditions used to describe a gas—pressure, volume, temperature, and number of moles (quantity)—are all related, along with R, the universal gas law constant, in the following formula:
PV = nRT
where P = pressure (atm), V = volume (L), n = number of moles (mol), R = 0.08206 L · atm/mol · K, and T = temperature (K).
Now try an example using the ideal gas law equation.
Example
A 16.0 g sample of methane gas, CH4, the gas used in chemistry lab, has a volume of 5.0 L at 27ºC. Calculate the pressure.
Explanation
Looking at all the information given, you have a mass, a volume, and a temperature, and you need to find the pressure of the system. As always, start by checking your units. You must first convert 16.0 g of CH4 into moles: 16.0 g CH41 mol CH4/16.0 g CH4 = 1 mol of methane. The volume is in the correct units, but you must convert the temperature into Kelvins: 27 + 273 = 300K. Now you’re ready to plug these numbers into the ideal gas law equation:
PV = nRT
(P) (5.0 L) = (1.0 mol) (0.0821 Latm/molK) (300K), so P = 4.9 atm
Don’t let the math scare you. Remember that your test will be all multiple choice. You may be asked for proper setup, or at least you will have answers to choose from, and you won’t have to do these lengthy calculations without a calculator. These examples are only meant to give you practice using the gas law equations.
 Jump to a New ChapterIntroduction to the SAT IIIntroduction to the SAT II Chemistry TestStrategies for Taking the SAT II Chemistry TestThe Structure of MatterThe States of MatterReaction TypesStoichiometryEquilibrium and Reaction RatesThermodynamicsDescriptive ChemistryLaboratoryBasic Measurement and Calculation ReviewChemical Formulas Review: Nomenclature and Formula WritingPractice Tests Are Your Best Friends
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