gas law

1. STUDENT: LE KIM HOANG PHAM
ID: 6109320231
ORAL QUALIFY EXAMINATION
13th December 2018
THAMMASAT UNIVERSITY
FACULTY OF SCIENCE AND TECHNOLOGY
GAS LAWS
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2. OPENING THOUGHTS…
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Have you ever:
Seen the sky lanterns in loy krathong?
Had a soda bottle spray all over you?
Baked (or eaten) a nice, fluffy cake?
How does the gases work?
What is gas?
How does the gases quantitative work?

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GASES BEHAVIOR
Bromine evaporates at room temperature
to produce a dense gas, shown being
poured from a flask. That gas used to
disinfect swimming pools and hot tubs
Pressure
Volume
Amount (moles)
Temperature
Gas behavior based on the
following properties:
How do they all relate?

4. PRESSURE OF GAS
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Barometer
A mercury barometer
The height h is proportional to
the barometric pressure. For
that reason, the pressure is
often given as the height of the
mercury column, in units of
millimeters of mercury, mmHg
Pressure is defined as the
force the gas exerts on a
given area of the container
in which it is contained.
The SI unit for pressure is
the Pascal, Pa.
Unit relationship:
-Pascal, (Pa) kg/(m.s2)
-Atmosphere (atm) 1 atm = 1.01325 x 105
Pa = 100 kPa
-mmHg, or torr 760 mmHg =1 atm
-Bar 1.01325 bar = 1 atm

5. VOLUME OF GAS
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Volume of gas is the three-dimensional space
inside the container holding the gas.
Think of a 2-liter bottle of soda to get
an idea of how big a liter is.
(OK, how big two of them are…)
Unit : m3/ liter, L.

6. TEMPERATURE OF GAS
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Temperature is the measurement of heat…or how
fast the particles are moving. Gases, at room
temperature, have a lower boiling point than things
that are liquid or solid at the same temperature.
Water will freeze at zero degrees
Celsius. However alcohol will not
freeze at this temperature.
ºF
ºC
K
-459 32 212
-273 0 100
0 273 373

7. AMOUNT OF GAS
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Amount of substance is tricky. As we’ve already
learned, the SI unit for amount of substance is the mole,
mol. Since we can’t count molecules, we can convert
measured mass (in kg) to the number of moles, n, using
the molecular or formula weight of the gas.
By definition, one mole of a substance contains
approximately 6.022 x 1023 particles of the
substance. You can understand why we use mass
and moles!

8. L E K I M H O A N G P H A M - 6 1 0 9 3 2 0 2 3 1 8
THE EMPIRICAL GAS LAWS
Boyle’s Law
P
V
PAVA = PBVB
Relating pressure and volume
Compressibility
One characteristic property of a gas
(1661)
1520 mm Hg760 mm Hg 2280 mm Hg
V ̴ 1/P

9. L E K I M H O A N G P H A M - 6 1 0 9 3 2 0 2 3 1 9
THE EMPIRICAL GAS LAWS
Relating volume and temperature
V
T
𝐕 𝐀
𝐓 𝐀
=
𝐕 𝐁
𝐓 𝐁
Charles’ Law
(P = 1.00 atm)

10. L E K I M H O A N G P H A M - 6 1 0 9 3 2 0 2 3 1 10
THE EMPIRICAL GAS LAWS
Relating pressure and temperature
P
T
𝐏 𝑨
𝐓 𝑨
=
𝐏 𝑩
𝐓 𝑩
Gay-Lussac’s Law
For a gas at constant mass and volume, the pressure
and temperature are directly related.
A B

11. L E K I M H O A N G P H A M - 6 1 0 9 3 2 0 2 3 1 11
THE EMPIRICAL GAS LAWS
It is a law that combines the previous laws into one
𝑽 𝟏 𝐏𝟏
𝐓𝟏
=
𝑽 𝟐 𝐏𝟐
𝐓𝟐
T2P1V1= T1P2V2
temperature
pressure
volume

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THE EMPIRICAL GAS LAWS
temperature
volume
pressure
How does it work…?pressure

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THE EMPIRICAL GAS LAWS
Avogadro’s Law: Relating Volume and Amount
V
n
Equal volumes of gases contain equal
numbers of moles
at constant temp & pressure
true for any ideal gas
𝐕𝟏
𝐧 𝟏
=
𝐕𝟐
𝐧 𝟐
 1 mole = 6.02 x 1023 molecules (Avogadro’s number)
 Standard conditions (T = 0 ºC, P = 1 atm)
The molar gas volume (Vm) = 22.4 L/mol

14. P.V= 𝐧. 𝐑. 𝐓
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THE IDEAL GAS EQUATION
The ideal gas law is related all the information (P, T, and
amount of gas) contained in Boyle’s, Charles’s, and Avogadro’s
laws in one equation
The molar gas constant, R, is the constant of
proportionality relating the molar volume of a
gas to T/P
Boyle’s law and Charles’s law into the equation
V= 𝐜𝐨𝐧𝐬𝐭𝐚𝐧𝐭
𝐓
𝐏𝐀𝐭 𝟏 𝐦𝐨𝐥𝐞 𝐨𝐟 𝐠𝐚𝐬
C𝐨𝐧𝐬𝐭𝐚𝐧𝐭 amount of gas (mole) denote as R
V Mole volume (Vm)
V 𝐦 =
𝐑.𝐓
𝐏
𝐀𝐭 𝐧 𝐦𝐨𝐥𝐞 𝐨𝐟 𝐠𝐚𝐬
nV 𝐦 =
𝐧.𝐑.𝐓
𝐏
V(total volume)
Value of R:
1. 0.082058 L.atm/(K.mol)
2. 8.3145 J/(Kmol) = 8.3145 kg.m2/(s2.K.mol)
= 8.3145 kPa.dm3/(K.mol)
3. 1.9872 cal/(K.mol)

15. L E K I M H O A N G P H A M - 6 1 0 9 3 2 0 2 3 1 15
STOICHIOMETRY PROBLEMS INVOLVING
GAS VOLUMES
Problem:
Suppose you heat 0.0100 mol of potassium chlorate, KClO3, in a test tube. How many
liters of oxygen can you produce at 298 K and 1.02 atm?
Solution:
2KClO3 2KCl + 3O2
MnO2
Δ2 mol 3 mol
0.01 mol X mol
X =
0.01 x 3
2
= 0.015 (mol)
The ideal gas law, PV = nRT, and solve for the
volume
V =
𝐧.𝐑.𝐓
𝐏
=
𝟎.𝟎𝟏𝟓 𝐦𝐨𝐥 𝐱 𝟎.𝟎𝟖𝟐𝟏 𝐋.
𝐚𝐭𝐦
𝐊.𝐦𝐨𝐥
𝐱 𝟐𝟗𝟖 (𝐊)
𝟏.𝟎𝟐 (𝐚𝐭𝐦)
= 0.360 L

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GAS MIXTURES
Partial Pressures and Mole Fractions
- Dalton’s law of partial pressures:
P = PA + PB + PC + …
- Mole fraction of A: nA =
𝒏 𝑨
𝒏
=
𝑷 𝑨
𝑷

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SUMMARY
temperature
pressure
volume
 Relationship of gas properties
 The ideal gas equation
V=
𝒏.𝐑.𝐓
𝐏
 Partial Pressures and Mole Fractions
- Dalton’s law of partial pressures:
P = PA + PB + PC + …
- Mole fraction of A: nA =
𝒏 𝑨
𝒏
=
𝑷 𝑨
𝑷

18. THANK YOU!
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