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Chemistry LibreTexts

Constants and Conversions

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Joules = CoulombsVolts = Kilogramsmeters2seconds2

Power = CurrentVolts in units Joulesseconds

Keep in mind that there are two systems for using units - the MKS and cgs system. The MKS system uses meters, kilograms, and seconds together. The cgs system uses centimeters, grams, and seconds together

Also keep in mind that there are multiple meanings for R. R, like V, is a commonly used letter for formulas in the physical sciences. It is imperative to keep track of what R you are talking about. For physical chemistry specifically, R can mean four different things.

  1. Rydberg constant, R. Seen in E=R1n2
  2. Radial function, R. Seen in ψ=RnYm
  3. Bond length R. Seen in the moment of inertia formula for a rigid rotor I=μ R2
  4. Constant R. Seen in the ideal gas law PV=nRT
Conversions between energy units
  joule kJmol eV Eh cm1 Hz
1joule 1 6.022x1020 6.241x1018 2.294x1017 5.034x1022 1.509x1033
1kJmol 1.660x1021 1 1.036x102 3.809x104 83.596 2.506x1012
1eV 1.602x1019 96.485 1 3.675x102 8065.54 2.418x1014
1Eh 4.359x1018 2625.500 27.211 1 2.1947x105 6.580x1015
1cm1 1.986x1023 1.196x102 1.239x104 4.556x106 1 2.998x1010
1Hz 6.626x1034 3.990x1013 4.135x1015 1.159x1016 3.336x1011 1
Values of various physical constants
Constant Symbol Value
Atomic mass constant mu 1.6605402x1027kg
Avogadro constant NA 6.0221367x1023mol1
Bohr magneton βB = e2me 9.2740154x1024J T1
Bohr radius a0 = 4πϵ0mee2 5.29177249x1011m
Boltzmann constant kB 1.380658x1023J K1
.695038cm1
Electron rest mass me 9.1093897x1031kg
Gravitational constant G 6.67259x1011m3 kg1 s2
Molar gas constant R 8.314510J K1 mol1

.0831451dm3 bar K1 mol1

.0820578dm3 atm K1 mol1
Molar volume, ideal gas, one bar, 0C - 22.71108L mol1
Molar volume, ideal gas, one atm, 0C - 22.41409L mol1
Nuclear magneton μn = e2mp 5.0507866x1027J T1
Permittivity of vacuum ϵ0 8.854187816x1012C2 J1 m1
4πϵ0 1.112650056x1010C2 J1 m1
Planck constant h 6.6260755x1034J s
1.05457266x1034J s
Proton charge e 1.60217733x1019C
Proton magnetogyric ratio γp 2.67522128x108s1 T1
Proton rest mass mp 1.6726231x1027kg
Rydberg constant (Bohr) R = mee48ϵ20h2 2.1798736x1018J
109737.31534cm1
Rydberg constant (experimental) Rh 109677.581cm1
Speed of light in vacuum

c

299792458m s1

Constants and Conversions is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts.

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