Chem 161 Practice Problems 2

# Chem 161 Practice Problems 2 - Boyles Law Robert Boyle...

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Boyle’s Law Robert Boyle investigated the relationship of pressure and volume for a fixed amount of gas in 1650. Boyle’s actual data is shown below. Vol (inch 3 ) P (mm Hg) PV 117.5 12.0 141 87.2 16.0 140 70.3 20.0 141 58.8 24.0 141 44.2 32.0 141 35.3 40.0 141 29.1 48.0 140 Equivalent Statements of Boyle’s Law Pressure and Volume are inversely proportional. PV = constant P 1 V 1 = P 2 V 2 (constant temperature, amount) If pressure is changed by multiplying by factor n, volume is changed by multiplying by factor . For all statements of Boyle’s Law, temperature and amount of gas remain the same.

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Plotting Boyle’s Data 10 20 30 40 50 Pressure 25 50 7 5 100 125 Volume Pressure vs. Volume Pressure Example Problem A gas has a volume of 125 mL at a pressure of 1.00 atm. What is its volume if the pressure is increased to 1.50 atm? P 1 V 1 = P 2 V 2 125(1.00) = 1.50V 2 V 2 = 83.3 mL Alternate analysis: The pressure increases by a factor of 1.50. The volume must therefore decrease by a factor of 1.50, due to the inverse proportion. Final volume = 50 . 1 volume initial = 50 . 1 125 = 83.3 mL
Boyle’s Law determines how volume is affected by pressure changes. The inverse proportion of pressure and volume assumes no change of temperature. The volume of a gas is also dependent on temperature. The volume of a gas at constant pressure increases linearly with temperature. Some sample data is shown in the table below. For these data, the pressure and amount of gas is constant. V T ( o C) 48.0 0 51.5 20 55.0 40 58.5 60 62.1 80 65.6 100 A sample plot is shown below. 0 20 40 60 80 Volume -300 -200 -100 0 100 200 Temp (deg C) Volume vs Temperature Volume

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When the linear graph is extrapolated to zero volume, the line hits the axis at -273 o C. Calling this point the origin (Volume = 0, Temperature = 0), we get a proportional relationship between volume and temperature: one in which there is a constant ratio. Such a relationship will always hold for a straight line coming to the origin.
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Chem 161 Practice Problems 2 - Boyles Law Robert Boyle...

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