© 2013 pearson education, inc. chapter 7, section 8 general, organic, and biological chemistry...

© 2013 Pearson Education, Inc. Chapter 7, Section 8

General, Organic, and Biological Chemistry

Fourth EditionKaren Timberlake

7.8The Ideal Gas Law

Chapter 7Gases

© 2013 Pearson Education, Inc.Lectures


The four properties used in the measurement of a gas, pressure (P), volume (V), temperature (T), and amount (n),

can be combined to give a single expression called theideal gas law. PV = nRT

Ideal Gas Law

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Rearranging the ideal gas law equation shows that thefour gas properties equal a constant, R.

To calculate the value of R, we substitute the STPconditions for molar volume into the expression:

R, Ideal Gas Constant

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Another value for the universal gas constant, R, is obtained using mmHg for the STP pressure. What is the value of R when a pressure of 760 mmHg rather than 1.00 atm is used?

Learning Check

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Another value for the universal gas constant, R, isobtained using mmHg for the STP pressure. Whatis the value of R when a pressure of 760 mmHgrather than 1.00 atm is used?

Solution

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Unit Summary for R, the Ideal Gas Constant

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Guide to Using the Ideal Gas Law

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Dinitrogen oxide (N2O), laughing gas, is used by dentists as an anesthetic. If a 20.0 L tank of laughing gas contains 2.86 moles of N2O at 23 C, what is the pressure (mmHg) in the tank?

Learning Check

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If a 20.0 L tank of laughing gas contains 2.86 moles ofN2O at 23 ˚C, what is the pressure (mmHg) in the tank?

Step 1 State the given and needed quantities. Analyze the Problem.

Solution

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Step 2 Rearrange the ideal gas law equation to solve for the needed quantity.

Solution

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Step 3 Substitute the gas data into the equation and calculate the needed quantity.

Solution

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Ideal Gas Law and Molar Mass

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Learning Check

A cylinder contains 5.0 L of an unknown gas at 20.0 ˚C and 0.85 atm. If the mass of the gas in the cylinder is 5.8 g, what is the molar mass of the gas?

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A cylinder contains 5.0 L of an unknown gas at 20.0 ˚Cand 0.85 atm. If the mass of the gas in the cylinder is5.8 g, what is the molar mass of the gas?

Step 1 State the given and needed quantities. Analyze the Problem

Solution

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A cylinder contains 5.0 L of an unknown gas at 20.0 ˚Cand 0.85 atm. If the mass of the gas in the cylinder is5.8 g, what is the molar mass of the gas?Step 2 Rearrange the ideal gas law equation to solve for the number of moles.

Step 3 Obtain the molar mass by dividing the given number of grams by the number of moles.

Solution

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Chemical Reactions and the Ideal Gas Law

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Learning Check

Nitrogen gas reacts with hydrogen gas to produce ammonia (NH3) gas. How many liters of NH3 can be produced at 0.93 atm and 24 ˚C from a 16.0-g sample of nitrogen gas and an excess of hydrogen gas?

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Solution

How many liters of NH3 can be produced at 0.93 atm and24 ˚C from a 16.0-g sample of nitrogen gas and anexcess of hydrogen gas?

Step 1 State the given and needed quantities.

Analyze the Problem.

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Solution


Step 2 Write a plan to convert the given quantity to the needed moles.

grams molar moles mole−mole moles of N2 mass of N2 factor of NH3

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Step 3 Write the equalities for molar mass and mole– mole factors.

Solution

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Solution


Step 4 Set up the problem to calculate moles of needed quantity.

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Solution


Step 5 Convert the moles of needed to volume using

the ideal gas law equation.

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© 2013 pearson education, inc. chapter 7, section 8 general, organic, and biological chemistry...

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