Teori Kinetik Gas - Zainal Abidin

1. Teori Kinetik Gas
Zainal Abidin
SMAN 3 Bandar Lampung, 8 Maret 2014

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3. Persamaan Keadaan Gas Ideal
Pengertian Mol dan Massa Molekul
Massa molekul (M) suatu zat adalah massa
dalam kilogram dari satu kilomol zat.
Massa sebuah atom atau molekul
Hubungan massa dan mol

4. Lorenzo Romano Amedeo Carlo Avogadro di Quaregna e di Cerreto
Count of Quaregna and Cerreto (9 August
1776, Turin, Piedmont – 9 July 1856) was
an Italian scientist. He is most noted for his
contributions to molecular theory, including what is
known as Avogadro's law. In tribute to him, the
number of elementary entities
(atoms, molecules, ions or other particles) in
1 mole of a substance, 6.02214179(30)×1023, is
known as theAvogadro constant.
http://en.wikipedia.org/wiki/Amedeo_Avogadro

5. Penurunan Persamaan Keadaan Gas Ideal
Jika suhu yang berada dalam bejana tertutup (tidak bocor)
dijaga tetap, tekanan gas berbanding terbalik dengan volumnya.
Hukum Boyle:
Jika tekanan gas yang berada dalam bejana tertutup
(tidak bocor) diajaga tetap, volum gas sebanding
dengan suhu mutlaknya.
Hukum CharlesGay Lussac:
Persamaan Boyle-Gay Lussac:

6. http://id.wikipedia.org/wiki/Joseph_Louis_Gay-Lussac
http://en.wikipedia.org/wiki/Robert_Boyle

7. Molecular Mass, the Mole, and Avogadro's Number
To set up atomic mass scale, a reference value (along with a unit) is
chosen for one of the elements. The unit is called the atomic mass unit
(symbol: u). By international agreement, the reference element is
chosen to be the most abundant type or isotope* of carbon, which is
called carbon-12. Its atomic mass * is defined to be exactly twelve
atomic mass units, or 12 u. The relationship between the atomic mass
unit and the kilogram is
7

8. A portion of the periodic table showing the atomic number
and atomic mass of each element. In the periodic table it is
customary to omit the symbol “u” denoting the atomic mass
unit.
8

9. The molecular mass of a molecule is the sum of the atomic
masses of its atoms.
Macroscopic amounts of materials contain large numbers of
atoms or molecules. Even in a small volume of gas, 1 cm3, for
example, the number is enormous. It is convenient to express
such large numbers in terms of a single unit, the gram-mole, or
simply the mole (symbol: mol). One gram-mole of a substance
contains as many particles (atoms or molecules) as there are
atoms in 12 grams of the isotope carbon-12.
12 grams of carbon-12 contain 6.022 × 1023 atoms. The
number of atoms per mole is known as Avogadro’s number NA,
after the Italian scientist Amedeo Avogadro (1776–1856):
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10. 10

11. The mass per mole (in g/mol) of a substance has
the same numerical value as the atomic or
molecular mass of the substance (in atomic mass
units).
11

12. Example 1. The Hope Diamond and
the Rosser Reeves Ruby
The Hope diamond (44.5 carats), which is almost pure carbon.
The Rosser Reeves ruby (138 carats), which is primarily
aluminum oxide (Al2O3). One carat is equivalent to a mass of
0.200 g.
Determine (a) the number of carbon atoms in the diamond and
(b) the number of Al2O3 molecules in the ruby.
12

13. http://www.harrywinston.com/our-story/hope-diamond

14. http://smithsonianscience.org/2009/08/blue-hope-diamond-glows-an-erie-red-after-exposure-to-ultraviolet-light/
The 45.52 carat, deep-blue Hope Diamond is shown here inside its surrounding pendant
of 16 pear- and cushion-cut white diamonds. (Photo by Chip Clark)

15. Rosser Reeves Star Ruby [G4257]
http://geogallery.si.edu/index.php/en/1001784/rosser-reeves-star-ruby

16. The Rosser Reeves Ruby
This 138.7 carat ruby is from Sri
Lanka and was owned by Rosser
Reeves. The description: "This is one
of the world's largest and finest star
rubies, with superb color and a welldefined star. Rosser Reeves, an
American advertising executive,
carried it as a lucky stone and called
it his 'baby'."
http://hyperphysics.phy-astr.gsu.edu/hbase/minerals/ruby.html

17. (a) m = (44.5 carats)[(0.200 g)/(1 carat)] = 8.90 g
(b) m = (138 carats)[(0.200 g)/(1 carat)] = 27.6 g.
Calculations like those in part (a) reveal that the Rosser Reeves ruby
contains 0.271 mol or
17

18. The Ideal Gas Law
An ideal gas is an idealized model for real gases that
have sufficiently low densities.
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19. Persamaan keadaan gas ideal:
Massa jenis gas (ρ):
Persamaan keadaan gas ideal:
Tetapan Boltzmann

20. Ludwig Eduard Boltzmann
(February 20, 1844 – September 5, 1906) was
an Austrian physicist and philosopher whose
greatest achievement was in the development
of statistical mechanics, which explains and
predicts how the properties of atoms (such
as mass, charge, and structure) determine the
physical properties of matter (such as
viscosity, thermal conductivity, and diffusion).
http://en.wikipedia.org/wiki/Ludwig_Boltzmann

21. The absolute pressure of an ideal gas is proportional to the
number of molecules or, equivalently, to the number of moles n
of the gas (P n).
P
nT/V.
IDEAL GAS LAW
The absolute pressure P of an ideal gas is directly
proportional to the Kelvin temperature T and the
number of moles n of the gas and is inversely
proportional to the volume V of the gas: P = R(nT/V).
In other words,
where R is the universal gas constant and has the value of
8.31 J/(mol·K).
21

22. The constant term R/NA is referred to as Boltzmann’s
constant, in honor of the Austrian physicist Ludwig
Boltzmann (1844–1906), and is represented by the symbol
k:
22

23. Example 2. Oxygen in the Lungs
In the lungs, the respiratory membrane separates tiny sacs of
air (absolute pressure = 1.00 × 105 Pa) from the blood in the
capillaries. These sacs are called alveoli, and it is from them
that oxygen enters the blood. The average radius of the
alveoli is 0.125 mm, and the air inside contains 14% oxygen.
Assuming that the air behaves as an ideal gas at body
.
temperature (310 K), find the number of oxygen molecules in
one of the sacs.
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24. One mole of an ideal gas occupies a volume of 22.4
liters at a temperature of 273 K (00C) and a pressure
of one atmosphere (1.013 × 105 Pa). These
conditions of temperature and pressure are known as
standard temperature and pressure (STP).
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25. Kinetic Theory of Gases
25

26. THE DISTRIBUTION OF
MOLECULAR SPEEDS
26

27. KINETIC THEORY
The pressure that a gas exerts
is caused by the collisions of its
molecules with the walls of the
container.
27

28. A gas particle is shown
colliding elastically with
the right wall of the
container and
rebounding from it.
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29. 29

30. 30

31. Tekanan dan Energi Kinetik menurut
Teori Kinetik Gas
Beberapa asumsi tentang gas ideal:
(1) Gas terdiri dari molekul-molekul yang
sangat banyak dan jarak misah antar
molekul jauh lebih besar dari pada
ukurannya.
(2) Molekul-molekul memenuhi hukum gerak
Newton, tetapi secara keseluruhan
mereka bergerak lurus secara acak
dengan kecepatan tetap.
(3) Molekul-molekul mengalami tumbukan lenting sempurna satu sama
lain dan dengan dinding wadahnya.
(4) Gaya-gaya antar molekul dapat diabaikan, kecuali selama satu
tumbukan yang berlangsung sangat singkat.
(5) Gas yang dipertimbangkan adalah suatu zat tunggal, sehingga
semua molekul adalah identik.

32. Formulasi Tekanan Gas dalam Wadah Tertutup
L³ adalah volum gas V.
Tekanan gas:

33. Energi Kinetik Rata-rata Molekul Gas
Energi kinetik rata-rata
(1) Suhu gas tidak mengandung
besaran N/V
(2) Suhu gas hanya berhubungan
dengan gerak molekul

34. Conceptual Example 3
Does a Single Particle Have a
Temperature?
Each particle in a gas has kinetic energy. Furthermore, the
equation
establishes the relationship
between the average kinetic energy per particle and the
temperature of an ideal gas. Is it valid, then, to conclude that
a single particle has a temperature?
A single gas particle does
not have a temperature.
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35. Kelajuan Efektif Gas

36. Example 4.
The Speed of Molecules in Air
Air is primarily a mixture of nitrogen N2 (molecular mass =
28.0 u) and oxygen O2 (molecular mass = 32.0 u). Assume
that each behaves as an ideal gas and determine the rms
speeds of the nitrogen and oxygen molecules when the
temperature of the air is 293 K.
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37. 37

38. Hubungan Kelajuan Efektif Gas
dengan Suhu Mutlaknya
Kelajuan efektif:

39. Perbandingan Kelajuan Efektif Berbagai Gas
Kelajuan efektif:

40. Menghitung Kelajuan Efektif dari
Data Tekanan

41. Teorema Ekipartisi Energi
Energi kinetik monoatomik:
Untuk suatu sistem molekul-molekul gas pada suhu
mutlak T dengan tiap molekul memiliki f derajat
kebebasan, rata-rata energi kinetik per molekul Ek
adalah

42. Derajat Kebebasan Molekul Gas Diatomik
Energi kinetik gas diatomik:
Gas diatomik dapat memiliki sampai tujuh derajat kebebasan.
Gas yang memiliki lebih dari dua atom (poliatomik) memiliki derajat
kebebasan yang lebih banyak dan getarannya juga lebih kompleks.

43. Energi Dalam Gas
Energi dalam suatu gas ideal didefinisikan
sebagai jumlah energi kinetik seluruh molekul
gas yang terdapat di dalam wadah tertutup.
Untuk gas monoatomik
Untuk gas diatomik

44. Diffusion
The process in which molecules move from a region of
higher concentration to one of lower concentration is called
diffusion. The host medium, such as the air or water, is
referred to as the solvent, while the diffusing substance,
like the perfume molecules, is known as the solute.
Relatively speaking, diffusion is a slow process, even in a
gas.
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45. Conceptual Example 5.
Why Diffusion Is Relatively Slow
In Example 4 we have seen
that a gas molecule has a
translational rms speed of
hundreds of meters per second
at room temperature. At such a
speed, a molecule could travel
across an ordinary room in just
a fraction of a second. Yet, it
often takes several seconds,
and sometimes minutes, for the
fragrance of a perfume to reach
the other side of a room. Why
does it take so long?
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46. When a perfume molecule diffuses through air, it
makes millions of collisions each second with air
molecules. The speed and direction of motion
change abruptly as a result of each collision.
Between collisions, the perfume molecule moves
in a straight line at a constant speed. Although a
perfume molecule does move very fast between
collisions, it wanders only slowly away from the
bottle because of the zigzag path resulting from
the collisions. It would take a long time for a
molecule to diffuse in this manner across a room.
Usually, however, convection currents are present
and carry the fragrance across the room in a
matter of seconds or minutes.
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47. (a) Solute diffuses through the channel from the region of higher
concentration to the region of lower concentration. (b) Heat is
conducted along a bar whose ends are maintained at different
temperatures.
47

48. FICK’S LAW OF DIFFUSION
The mass m of solute that diffuses in a time t through a
solvent contained in a channel of length L and crosssectional area A is
where C is the concentration difference between the
ends of the channel and D is the diffusion constant.
SI Unit for the Diffusion Constant: m2/s
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49. Example 6.
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50. Large amounts of water can be given off by plants. It has
been estimated, for instance, that a single sunflower plant
can lose up to a pint of water a day during the growing
season. At figure shows a cross-sectional view of a leaf.
Inside the leaf, water passes from the liquid phase to the
vapor phase at the walls of the mesophyll cells. The water
vapor then diffuses through the intercellular air spaces and
eventually exits the leaf through small openings, called
stomatal pores. The diffusion constant for water vapor in air
is D = 2.4 × 10–5 m2/s. A stomatal pore has a cross-sectional
area of about A = 8.0 × 10–11 m2 and a length of about L =
2.5 × 10–5 m. The concentration of water vapor on the interior
side of a pore is roughly C2 = 0.022 kg/m3, while that on the
outside is approximately C1 = 0.011 kg/m3. Determine the
mass of water vapor that passes through a stomatal pore in
one hour.
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52. Concepts & Calculations Example 7.
Hydrogen Atoms in Outer Space
In outer space the density of matter is extremely low, about
one atom per cm3. The matter is mainly hydrogen atoms (m =
1.67 × 10–27 kg) whose rms speed is 260 m/s. A cubical box,
2.0 m on a side, is placed in outer space, and the hydrogen
atoms are allowed to enter. (a) What is the magnitude of the
force that the atoms exert on one wall of the box? (b)
Determine the pressure that the atoms exert. (c) Does outer
space have a temperature, and, if so, what is it?
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53. (a)
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54. (b)
(c)
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58. terima kasih