49. Argon is a monatomic gas, so f = 3 in Eq. 20-51, which provides

C

V

=

3

2

R =

3

2

 

8.31

J

mol

·K

 

1 cal

4.186 J

= 2.98

cal

mol

·C

◦

where we have converted Joules to calories (Eq. 19-12), and taken advantage of the fact that a Celsius
degree is equivalent to a unit change on the Kelvin scale. Since (for a given substance) M is effectively a
conversion factor between grams and moles, we see that c

V

(see units specified in the problem statement)

is related to C

V

by

C

V

= c

V

M

where M = mN

A

where m is the mass of a single atom (see Eq. 20-4).

(a) From the above discussion, we obtain

m =

M

N

A

=

C

V

/c

V

N

A

=

2.98/0.075

6.02

× 10

23

= 6.6

× 10

−23

g .

(b) The molar mass is found to be M = C

V

/c

V

= 2.98/0.075 = 39.7 g/mol which should be rounded

to 40 since the given value of c

V

is specified to only two significant figures.

Document Outline

• Main Menu
• Chapter 1 Measurement
• Chapter 2 Motion Along a Straight Line
• Chapter 3 Vectors
• Chapter 4 Motion in Two and Three Dimensions
• Chapter 5 Force and Motion I
• Chapter 6 Force and Motion II
• Chapter 7 Kinetic Energy and Work
• Chapter 8 Potential Energy and Conservation of Energy
• Chapter 9 Systems of Particles
• Chapter 10 Collisions
• Chapter 11 Rotation
• Chapter 12 Rolling, Torque, and Angular Momentum
• Chapter 13 Equilibrium and Elasticity
• Chapter 14 Gravitation
• Chapter 15 Fluids
• Chapter 16 Oscillations
• Chapter 17 Waves—I
• Chapter 18 Waves—II
• Chapter 19 Temperature, Heat, and the First Law of Thermodynamics
• Chapter 20 The Kinetic Theory of Gases
  • 20.1 - 20.10
    • 20.1
    • 20.2
    • 20.3
    • 20.4
    • 20.5
    • 20.6
    • 20.7
    • 20.8
    • 20.9
    • 20.10
  • 20.11 - 20.20
    • 20.11
    • 20.12
    • 20.13
    • 20.14
    • 20.15
    • 20.16
    • 20.17
    • 20.18
    • 20.19
    • 20.20
  • 20.21 - 20.30
    • 20.21
    • 20.22
    • 20.23
    • 20.24
    • 20.25
    • 20.26
    • 20.27
    • 20.28
    • 20.29
    • 20.30
  • 20.31 - 20.40
    • 20.31
    • 20.32
    • 20.33
    • 20.34
    • 20.35
    • 20.36
    • 20.37
    • 20.38
    • 20.39
    • 20.40
  • 20.41 - 20.50
    • 20.41
    • 20.42
    • 20.43
    • 20.44
    • 20.45
    • 20.46
    • 20.47
    • 20.48
    • 20.49
    • 20.50
  • 20.51 - 20.60
    • 20.51
    • 20.52
    • 20.53
    • 20.54
    • 20.55
    • 20.56
    • 20.57
    • 20.58
    • 20.59
    • 20.60
  • 20.61 - 20.70
    • 20.61
    • 20.62
    • 20.63
    • 20.64
    • 20.65
    • 20.66
    • 20.67
    • 20.68
    • 20.69
    • 20.70
  • 20.71 - 20.80
    • 20.71
    • 20.72
    • 20.73
    • 20.74
    • 20.75
    • 20.76
    • 20.77
    • 20.78
    • 20.79
    • 20.80
  • 20.81 - 20.90
    • 20.81
    • 20.82
    • 20.83
    • 20.84
    • 20.85
    • 20.86
    • 20.87
    • 20.88
    • 20.89
    • 20.90
  • 20.91 - 20.92
    • 20.91
    • 20.92
• Chapter 21 Entropy and the Second Law of Thermodynamics
• Chapter 22 Electric Charge
• Chapter 23 Electric Fields
• Chapter 24 Gauss’ Law
• Chapter 25 Electric Potential
• Chapter 26 Capacitance
• Chapter 27 Current and Resistance
• Chapter 28 Circuits
• Chapter 29 Magnetic Fields
• Chapter 30 Magnetic Fields Due to Currents
• Chapter 31 Induction and Inductance
• Chapter 32 Magnetism of Matter: Maxwell’s Equation
• Chapter 33 Electromagnetic Oscillations and Alternating Current
• Chapter 34 Electromagnetic Waves
• Chapter 35 Images
• Chapter 36 Interference
• Chapter 37 Diffraction
• Chapter 38 Special Theory of Relativity
• Chapter 39 Photons and Matter Waves
• Chapter 40 More About Matter Waves
• Chapter 41 All About Atoms
• Chapter 42 Conduction of Electricity in Solids
• Chapter 43 Nuclear Physics
• Chapter 44 Energy from the Nucleus
• Chapter 45 Quarks, Leptons, and the Big Bang