Physical Chemistry I - Semester 2 Outlines and Practice Questions
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Physical Chemistry I
(TKK-2246)
13/14 Semester 2
Instructor: Rama Oktavian
Email: rama.oktavian86@gmail.com
Office Hr.:
M.13-15, Tu. 13-15, W. 13-15, Th. 13-15, F. 09-11
Outlines
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Review
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A sealed flask with a capacity of 1 dm
3
contains 5 g of ethane. The flask is so
weak that it will burst if the pressure exceeds 1 MPa. At what temperature will the
pressure of the gas reach the bursting pressure ?
Review
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A perfect gas undergoes isothermal compression, which reduces its
volume by 1.80 dm
3
. The final pressure and volume of the gas are 1.97 bar and
2.14 dm
3
, respectively. Calculate the original pressure of the gas in (a) bar,
(b) Torr
Review
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A large cylinder for storing compressed gases has a volume of about 0.050 m3. If
the gas is stored under a pressure of 15 MPa at 300 K, how many moles of
gas are contained in the cylinder ?
What would be the mass of oxygen in such a cylinder ?
Review
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A manometer consists of a U-shaped tube containing a liquid. One side
is connected to the apparatus and the other is open to the atmosphere. The
pressure inside the apparatus is then determined from the difference in
heights of the liquid. Suppose the liquid is water, the external pressure is
770 Torr, and the open side is 10.0 cm lower than the side connected to the
apparatus. What is the pressure in the apparatus? (The density of water at
25°C is 0.99707 g cm
−3
.)
Molar mass of ideal gas
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Ideal gas equation
Intensive properties and
measurable
Molar mass of ideal gas
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Gas density
Density is higher
1. for gases with a higher molar mass Gases
2. at higher pressures
3. at lower temperatures
Molar mass of ideal gas
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Example
if chemical analysis of a gas yields an empirical formula (CH 2 )n, then the
molar mass must be some multiple of 14 g/mol ; the possibilities are 28, 42, 56,
70, and so on. If a molar mass determination using Eq. (2. 20) yields a
value of 54 g/mol, then we may conclude that n = 4 and that the material
is one of the butenes.
Molar mass of ideal gas
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Problem : Calculation of Molecular Weight of a
Natural Gas - Methane
A sample of natural gas is collected at 25.0 C in a 250.0 ml
flask. If the sample had a mass of 0.118 g at a pressure of 550.0 torr,
what is the molecular weight of the gas?
Use the ideal gas law to calculate n, then calculate the molar mass.
Molar mass of ideal gas
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Problem
At 100°C and 1.60 kPa, the mass density of phosphorus vapour is
0.6388 kg m
−3
. What is the molecular formula of phosphorus under these
conditions?
Molar mass of ideal gas
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Problem
A series of measurements are made in order to determine the molar mass of an
unknown gas. First, a large flask is evacuated and found to weigh 134.567 g. It is
then filled with the gas to a pressure of 735 torr at 31°C and reweighed; its mass
is now 137.456 g. Finally, the flask is filled with water at 31°C and found to weigh
1067.9 g. (The density of the water at this temperature is 0.997 g/mL.) Assuming
that the ideal-gas equation applies, calculate the molar mass of the unknown gas.
Gas mixture
Air is an example of an ideal gas mixture and has the following approximate
composition.
Component
% by Volume
N2
78.10
O2
20.95
Argon
0.92
CO2 + trace elements
0.03
Gas mixture
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The total mass of the mixture
m
m
and the total moles of mixture
N
m
are
defined as
Gas mixture
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Volume concentration
Unit : mol/m
3
Volume concentration
molarity
Gas mixture
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The composition of a gas mixture is described by specifying either the
mass
fraction mf
i
or the
mole fraction y
i
of each component
i
.
Note that
Dalton’s law
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We define the partial pressure of each gas in the mixture as the pressure the
gas would exert if it were alone in the container of volume V at temperature T
Dalton’s law
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Dalton’s law
Dalton’s law
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pressure depends on the total number of gas
particles, not on the types of particles.
•
the total pressure exerted by gases in a
mixture is the sum of the partial pressures of
those gases.
P
T
= P
1
+ P
2
+ P
3
+.....
Dalton’s law
Dalton’s law
Partial pressures are simply related to the mole fractions of the gases
in the mixture
Dalton’s law
Partial pressures are simply related to the mole fractions of the gases
in the mixture
Dalton’s law
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If I place 3 moles of N
2
and 4 moles of O
2
in a 35 L container at a temperature
of 25°C, what will the pressure of the resulting mixture of gases be?
What’s the partial pressure of carbon dioxide in a container that holds 5
moles of carbon dioxide, 3 moles of nitrogen, and 1 mole of hydrogen and
has a total pressure of 1.05 atm?
Dalton’s law
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A vessel of volume 22.4 dm3contains 1.5 mol H2and 2.5 mol N2 at
273.15 K. Calculate (a) the mole fractions of each component, (b) their
partial pressures, and (c) their total pressure
Dalton’s law
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This explains why people usually difficult to breathe in high altitude place
even the concentration of oxygen is same (21%)
The transfer of oxygen molecules from the lungs to the bloodstream is
dependent on a pressure gradient.
Exercise and learning check
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Ch. 1 Atkin’s Physical chemistry 8
th
ed. Numerical problems no:
1.4
1.5
1.6
Take-home assignment – Theoretical problem 1.24
Chapter 2 Castellan Physical chemistry 3
rd
ed. Problems no:
2.9
2.13
Dive into Physical Chemistry I with this detailed outline covering topics such as molar mass of gas, gas mixtures, and ideal gas equations. Practice questions on gas pressure, volume, and temperature relationships are included for self-assessment. Learn how to calculate molar mass, determine gas density, and solve problems involving ideal gases. Enhance your understanding of key concepts in physical chemistry with this comprehensive study material.
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Presentation Transcript
13/14 Semester 2 Physical Chemistry I (TKK-2246) Instructor: Rama Oktavian Email: rama.oktavian86@gmail.com Office Hr.: M.13-15, Tu. 13-15, W. 13-15, Th. 13-15, F. 09-11
Outlines 1. Review 2. Molar mass of gas 3. Molar mass of volatile component 4. Gas mixture
Review Learning check Learning check A sealed flask with a capacity of 1 dm3 contains 5 g of ethane. The flask is so weak that it will burst if the pressure exceeds 1 MPa. At what temperature will the pressure of the gas reach the bursting pressure ?
Review Learning check Learning check A perfect gas undergoes isothermal compression, which reduces its volume by 1.80 dm3. The final pressure and volume of the gas are 1.97 bar and 2.14 dm3, respectively. Calculate the original pressure of the gas in (a) bar, (b) Torr
Review Learning check Learning check A large cylinder for storing compressed gases has a volume of about 0.050 m3. If the gas is stored under a pressure of 15 MPa at 300 K, how many moles of gas are contained in the cylinder ? What would be the mass of oxygen in such a cylinder ?
Review Learning check Learning check A manometer consists of a U-shaped tube containing a liquid. One side is connected to the apparatus and the other is open to the atmosphere. The pressure inside the apparatus is then determined from the difference in heights of the liquid. Suppose the liquid is water, the external pressure is 770 Torr, and the open side is 10.0 cm lower than the side connected to the apparatus. What is the pressure in the apparatus? (The density of water at 25 C is 0.99707 g cm 3.)
Molar mass of ideal gas Determination of molar mass for ideal gas Determination of molar mass for ideal gas Ideal gas equation PV = nRT w n = M Intensive properties and measurable w RT = = M RT V P P
Molar mass of ideal gas Determination of molar mass for ideal gas Determination of molar mass for ideal gas Gas density w RT = = M RT V P P Density is higher 1. for gases with a higher molar mass Gases 2. at higher pressures 3. at lower temperatures
Molar mass of ideal gas Determination of molar mass for ideal gas Determination of molar mass for ideal gas Example if chemical analysis of a gas yields an empirical formula (CH 2 )n, then the molar mass must be some multiple of 14 g/mol ; the possibilities are 28, 42, 56, 70, and so on. If a molar mass determination using Eq. (2. 20) yields a value of 54 g/mol, then we may conclude that n = 4 and that the material is one of the butenes.
Molar mass of ideal gas Determination of molar mass for ideal gas Determination of molar mass for ideal gas Problem : Calculation of Molecular Weight of a Natural Gas - Methane A sample of natural gas is collected at 25.0 C in a 250.0 ml flask. If the sample had a mass of 0.118 g at a pressure of 550.0 torr, what is the molecular weight of the gas? Use the ideal gas law to calculate n, then calculate the molar mass.
Molar mass of ideal gas Determination of molar mass for ideal gas Determination of molar mass for ideal gas Problem At 100 C and 1.60 kPa, the mass density of phosphorus vapour is 0.6388 kg m 3. What is the molecular formula of phosphorus under these conditions?
Molar mass of ideal gas Determination of molar mass for ideal gas Determination of molar mass for ideal gas Problem A series of measurements are made in order to determine the molar mass of an unknown gas. First, a large flask is evacuated and found to weigh 134.567 g. It is then filled with the gas to a pressure of 735 torr at 31 C and reweighed; its mass is now 137.456 g. Finally, the flask is filled with water at 31 C and found to weigh 1067.9 g. (The density of the water at this temperature is 0.997 g/mL.) Assuming that the ideal-gas equation applies, calculate the molar mass of the unknown gas.
Gas mixture Air is an example of an ideal gas mixture and has the following approximate composition. Component N2 O2 Argon CO2 + trace elements % by Volume 78.10 20.95 0.92 0.03
Gas mixture Properties of gas mixture Properties of gas mixture k gases T = TmV = Vm P = Pmm = mm The total mass of the mixture mm and the total moles of mixture Nm are defined as k k = = and m m N N m i m i = = 1 1 i i
Gas mixture Properties of gas mixture Properties of gas mixture Volume concentration Unit : mol/m3 Volume concentration molarity
Gas mixture Properties of gas mixture Properties of gas mixture The composition of a gas mixture is described by specifying either the mass fraction mfior the mole fraction yiof each component i. m m N N = = and i i mf y i i m m Note that k k = =1 and 1 mf y i i = = 1 1 i i
Daltons law Ideal gas law for gas mixture Ideal gas law for gas mixture We define the partial pressure of each gas in the mixture as the pressure the gas would exert if it were alone in the container of volume V at temperature T
Daltons law Partial pressure Partial pressure Dalton s law
Daltons law Dalton s Law of Partial Pressures indicates that pressure depends on the total number of gas particles, not on the types of particles. the total pressure exerted by gases in a mixture is the sum of the partial pressures of those gases. PT = P1 + P2 + P3 +.....
Daltons law Partial pressures are simply related to the mole fractions of the gases in the mixture p n RT V 1= 1 p n RT V t
Daltons law Partial pressures are simply related to the mole fractions of the gases in the mixture
Daltons law Learning check Learning check If I place 3 moles of N2 and 4 moles of O2 in a 35 L container at a temperature of 25 C, what will the pressure of the resulting mixture of gases be? What s the partial pressure of carbon dioxide in a container that holds 5 moles of carbon dioxide, 3 moles of nitrogen, and 1 mole of hydrogen and has a total pressure of 1.05 atm?
Daltons law Learning check Learning check A vessel of volume 22.4 dm3contains 1.5 mol H2and 2.5 mol N2 at 273.15 K. Calculate (a) the mole fractions of each component, (b) their partial pressures, and (c) their total pressure
Daltons law Dalton s law application in atmosphere Dalton s law application in atmosphere This explains why people usually difficult to breathe in high altitude place even the concentration of oxygen is same (21%) The transfer of oxygen molecules from the lungs to the bloodstream is dependent on a pressure gradient.
Exercise and learning check Problems Problems Ch. 1 Atkin s Physical chemistry 8th ed. Numerical problems no: 1.4 1.5 1.6 Take-home assignment Theoretical problem 1.24 Chapter 2 Castellan Physical chemistry 3rd ed. Problems no: 2.9 2.13
