Tag Archives: constants

Physical Constants, Prefixes, and Conversion Factors

Here are some useful physical constants, conversion factors, and unit prefixes. They are used in many calculations in chemistry, as well as in physics and other sciences.

Useful Constants

Acceleration of Gravity9.806 m/s2
Avogadro’s Number6.022 x 1023
Electronic Charge1.602 x 10-19 C
Faraday Constant9.6485 x 104 J/V
Gas Constant0.08206 L·atm/(mol·K)

8.314 J/(mol·K)

8.314 x 107 g·cm2/(s2·mol·K)

Planck’s Constant6.626 x 10-34 J·s
Speed of Light2.998 x 108 m/s
p3.14159
e2.718
ln x2.3026 log x
2.3026 R19.14 J/(mol·K)
2.3026 RT (at 25°C)5.708 kJ/mol

Common Conversion Factors

QuantitySI UnitOther UnitConversion Factor
Energyjoulecalorie
erg
1 cal = 4.184 J
1 erg = 10-7 J
Forcenewtondyne1 dyn = 10-5 N
LengthmetreAngstrom1 Å = 10-10 m = 10-8 cm = 10-1 nm
Masskilogrampound1 lb = 0.453592 kg
Pressurepascalbar
atmosphere
mm Hg
lb/in2
1 bar = 105 Pa
1 atm = 1.01325 x 105 Pa
1 mm Hg = 133.322 Pa
1 lb/in2 = 6894.8 Pa
TemperaturekelvinCelsius
Fahrenheit
1°C = 1 K
1°F = 5/9 K
Volumecubic metrelitre
gallon (U.S.)
gallon (U.K.)
cubic inch
1 L = 1 dm3 = 10-3 m3
1 gal (U.S.) = 3.7854 x 10-3 m3
1 gal (U.K.) = 4.5641 x 10-3 m3
1 in3 = 1.6387 x 10-6 m3

SI Unit Prefixes

FactorsPrefixSymbol
1012teraT
199gigaG
106megaM
103kilok
102hectoh
101decada
10-1decid
10-2centic
10-3millim
10-6microµ
10-9nanon
10-12picop
10-15femtof
10-18attoa

 

Table of Common Constants

Lasers

Series of different colored lasers. No matter the color, the speed of light is a constant. The speed of light is just one constant in this table of common constants. Credit: Pang Ka kit, Creative Commons

Here is a useful table of common constants. These physical constants appear time and again in chemistry and physics homework problems.

Why memorize them when you can just look them up.

I personally prefer to keep a sheet with these constants stuffed in the back of book. You can print up your own sheet with a PDF copy of the Table of Common Constants.

TABLE OF COMMON CONSTANTS

 Name SymbolValue
Speed of lightc299792458 m⋅s-1
Charge of an electrone1.602176565(35)×10−19 C
Universal gravitational constantG6.67384(80)×10-11 N⋅m2/kg2
Planck’s constanth6.626070040(81)×10−34 J⋅s
h4.135667662(25)×10−15 eV⋅s
Dirac’s constantħ1.054571800(13)×10−34 J⋅s
ħ6.582119514(40)×10−16 eV⋅s
Boltzmann’s constantk1.3806488(13)×10−23 J⋅K-1
8.6173324(78)×10−5 eV⋅K-1
Avogadro’s constantNA6.022140857(74)×1023 mol−1
Faraday’s constantF96485.3365(21) C⋅mol−1
Ideal gas constantR8.3144621(75) J⋅K−1⋅mol−1
Mass of an electronme9.10938291(40)×10−31 kg
0.510998928(11) MeV/c2
Mass of a protonmp1.672621777(74)×10−27 kg
938.272046(21) MeV/c2
Mass of a neutronmn1.674927351(74)×10−27 kg
939.565378(21) MeV/c2
Atomic mass unitu, amu or Da1.660538921(73)×10−27 kg
931.494061(21) MeV/c2
Permittivity of free spaceε08.854187817×10−12
Coulomb’s constant1/4πε08.9875517973681764×109 N⋅m2⋅C-2
Permeability of free spaceμ04π×10−7 N⋅A-2
Rydberg constantR1.0973731568539(55)×10−7 m-1
Bohr radiusa05.2917721092(17)×10−11 m