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Notes on The Gaseous State - Principles of Chemistry I | CHEM 1211, Study notes of Chemistry

Chapter 5 - The Gaseous State Material Type: Notes; Professor: Iordanov; Class: Principles of Chemistry I; Subject: Chemistry; University: Georgia Southwestern State University; Term: Fall 2011;

Typology: Study notes

2010/2011

Uploaded on 11/05/2011

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5.1 - Gas Pressure and Its Measurements
Define Pressure and its units.
oPressure is the force exerted per unit area of surface.
oThe units are: Pascal, Atmosphere, mmHg
Convert units of pressure.
oPascal (Pa) - kg/(mXs^2)
oAtmosphere (atm) - 1 atm = 1.01325x10^5 Pa, which is about 100 kPa
ommHg - 760 mmHg = 1 atm
5.2 - Empirical Gas Laws
Express Boyle's Law in words and as an equation.
oBoyle's Law is the volume of a sample of gas at a given temperature varies
immersely with the applied pressure.
oPV=constant (for a given amount of gas at a fixed temperature)
Use Boyle's Law.
oYou can use it to calculate the volume occupied by a gas when the pressure
changes.
oTake a 50.0-L gas cyliner of oxygen. The pressure of gas in the cylinder is 15.7 atm
at 21 deg C. What volume of oxygen can you get from the cylinder at 21 deg C if the
atmospheric pressure is 1.00 atm?
P1V1=P2V2
P1=15.7 atm -- V1=50.0 L -- P2=1.00 atm -- V2=?
P1/P2 * V1 = V2
15.7atm/1.00atm * 50L = 785-L
Express Charles's Law in words and as an equation.
oCharles's Law is the volume of a sample of gas at a constant pressure is directly
proportional to the absolute temperature.
oV/T=constant, where V is volume and T is temperature
Use Charles's Law.
oThe total volume of oxygen that can be obtained from a particular tank at 1.00 atm
and 21 deg C is 785 L. What would the volume of oxygen be if the temperature had
been 28 deg C?
V1/T1 = V2/T2
V1=785L -- T1=21 deg C (294K) -- V2=? -- T2=28 deg C (301K)
V1 x T2/T1 = V2
785L * 301K/294K = 804 L
Express the Combined Gas Law as an equation.
oV=constant x (T/P) or PV/T=constant
State Avogadro's Law.
oAvogadro's Law is equal volumes of any two gases at the same temperature and pressure
contain the same number of molecules.
Define Standard Temperature and Pressure (STP).
oSTP is the reference conditions for gases chosen by convention to be 0 degC and 1 atm
pressure.
5.3 - The Ideal Gas Law
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5.1 - Gas Pressure and Its Measurements

 Define Pressure and its units.

o Pressure is the force exerted per unit area of surface.

o The units are: Pascal, Atmosphere, mmHg

 Convert units of pressure.

o Pascal (Pa) - kg/(mXs^2)

o Atmosphere (atm) - 1 atm = 1.01325x10^5 Pa, which is about 100 kPa

o mmHg - 760 mmHg = 1 atm

5.2 - Empirical Gas Laws

 Express Boyle's Law in words and as an equation.

o Boyle's Law is the volume of a sample of gas at a given temperature varies

immersely with the applied pressure.

o PV=constant (for a given amount of gas at a fixed temperature)

 Use Boyle's Law.

o You can use it to calculate the volume occupied by a gas when the pressure

changes.

o Take a 50.0-L gas cyliner of oxygen. The pressure of gas in the cylinder is 15.7 atm

at 21 deg C. What volume of oxygen can you get from the cylinder at 21 deg C if the atmospheric pressure is 1.00 atm?

 P1V1=P2V

 P1=15.7 atm -- V1=50.0 L -- P2=1.00 atm -- V2=?

 P1/P2 * V1 = V

 15.7atm/1.00atm * 50L = 785-L

 Express Charles's Law in words and as an equation.

o Charles's Law is the volume of a sample of gas at a constant pressure is directly

proportional to the absolute temperature.

o V/T=constant, where V is volume and T is temperature

 Use Charles's Law.

o The total volume of oxygen that can be obtained from a particular tank at 1.00 atm

and 21 deg C is 785 L. What would the volume of oxygen be if the temperature had been 28 deg C?

 V1/T1 = V2/T

 V1=785L -- T1=21 deg C (294K) -- V2=? -- T2=28 deg C (301K)

 V1 x T2/T1 = V

 785L * 301K/294K = 804 L

 Express the Combined Gas Law as an equation.

o V=constant x (T/P) or PV/T=constant

 State Avogadro's Law.

o Avogadro's Law is equal volumes of any two gases at the same temperature and pressure

contain the same number of molecules.

 Define Standard Temperature and Pressure (STP).

o STP is the reference conditions for gases chosen by convention to be 0 degC and 1 atm

pressure.

5.3 - The Ideal Gas Law

 Learn the ideal gas law equation.

o The ideal gas law equation is PV=nRT, where n=the number of moles and

R=0.082058 Latm/(Kmol)

 Use the ideal gas law.

o How many grams of oxygen, O2, are there in a 50.0-L gas cylinder at 21 degC when

the oxygen pressure is 15.7 atm?

 PV=nRT

 P=15.7 atm -- V=50.0-L -- R=0.082058Latm/(Kmol) -- T=21 degC (294K)

 n=PV/RT

 n=(15.7atm)(50-L)/(0.082058Latm/(Kmol))(294K) = 32.5 mol

 32.5mol O2 * 32.0g O2/1mol O2 = 1.04 x 10^3 g O

 Calculate Gas Density.

o What is the density of Oxygen in grams per liter at 25 degC and 0.850 atm?

 P=0.850 atm -- V=1L -- T=25 degC (298K)

 (0.850atm)(1L)/ (R)(298K) = 0.0358 mol

 7.05g/0.0358mol = 197g/mol (Mm=m/n)

 Determine the molecular mass of a vapor.

o Use a 200.0-mL flask at 99 degC and a pressure of 733 mmHg thats filled with the

vapor of a volatile liquid. The mass of the substance in the flask is 0.970g. What is the molecular mass of the liquid?

 P= 733mmHg*(1atm/760mmHg) = 0.964 atm -- V=200mL (.2000L) -- T= 99C

(372K)

 (0.964atm)(.2000L) / (0.0821)(372K) = 0.1928/30.54 = 6.31 x 10^(-3) mol

 Grams vapor/molar vapor = molar mass

 0.970g/6.31x10^(-3) = 154 amu

 Use an equation to calculate gas density.

o 6 NaN3 + Fe2O3 --> 3 Na2O + 2Fe + 9 N

o How many grams of sodium azide would be required to provide 75-L of nitrogen gas

at 25C and 748mmHg?

 P= 748mmHg * 1atm/760mmHg = 0.984atm -- V=75L -- T=25C (298K)

 (0.984atm)(75L)/(0.0821)(298K) = 73.8/24.47 = 3.02 mol

 (3.02 mol N2)(6 mol NaN3/9 mol N2) = 2.01 mol NaN

 (2.01 mol NaN3)(65.01 g NaN3/1mol NaN3) = 131 g NaN