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CONSTANTS, UNITS, AND CONVERSION FACTORS in Analytical Chemistry

Analytical Chemistry SELECTED CONSTANTS, UNITS, AND CONVERSION FACTORS
[The uncertainty in the last digit(s) is shown italicized in parentheses]

Atomic mass constant:   mu = 1.660 538 73 x 10-27 kg 
Avogadro’s number: N = 6.022 141 99 (47) x 1023 mol-1

Boltzmann constant:  k  =  1.380 6503 (24) x 10-23 J/K
Elementary charge:  e = 1.602 176 462 (63) x 10-19  C                           
Faraday constant:  F  =  96 485.3415 (39) C/mol 
Molar gas constant:  R  =  8.314 472 (15) J/K-mol  =  1.9872 cal/K-mol 
                                    =  0.082 057 L-atm/K-mol  =  0.022 414 m3/mol at STP
Pi:  π  =  3.141 592 653 6
Planck’s constant:  h  =  6.626 068 76 (52) x 10-34 J-s       
Speed of light (in a vacuum):  c  =  2.999 792 458 (exact) x 108 m/s             
Stefan-Boltzmann constant:  σ  =  5.670 400 (40) x 10-8 W/m2-K4

Standard acceleration of gravity:  gn = 9.806 65 (exact) m/s2
  
Wein constant:  k  =  2.897 7686 (51) x 10-3 m-K  

Force:  1 N =  1 kg-m/s2
 
Joule:  1 J  =  1 N-m  =  1 kg-m2/s2  =  107
ergs = 1 V x 1 C  =  1 V-C = (J/C)(C)  
Power:  1 W = 1 J/s = 1 V x 1 A = 1 V-A = (J/C)(C/s)  
Electron Volt:   1 eV = 1.602 176 462 (63) x 10-19 J  =  3.827 x 10-20 cal   
Calorie (thermochemical):   1 cal  =  4.184 J     [Food “calorie” = 1 Cal = 1000 cal]

Length:  1 km  =  1000 m  =  0.62137 mi      1 in  =  2.54 cm (exactly)
Mass:  1 kg  =  1000 g    1 pound  =  453.59237 g
Pressure:  101 325 (exact) Pa  =  1 atm  =  760 mm Hg = 17.70 lb/in2

133.322 Pa  =  1 torr  =  1 mm Hg 105
 Pa  =  1 bar  1 Pa = 1 N/m2

Volume:  1 L  =  10-3 m3  =  1000 mL  =  1000 cm3  =  1.056710 quarts

Nernst factor:   (RT/nF) ln  =  (0.05916 V/n) log10 at 25 C 
nF/RT  =  38.920 n  V-1

RT/nF  =  0.02569/n  V  
     
∆G   =  -nFE   =  -RT(ln Keq)                 ∆G  =  -nFE  =  -RT(ln Q)
µ  = x + zσ/n1/2
   µ  = x + ts/n1/2
 

Some Less Common Multiplicative Prefixes: 
P  =  peta  =  1015
   T  =  tera  =  1012
   G  =  giga  =  109
   
n  =  nano  =  10-9
   p  =  pico  =  10-12
f  =  femto  =  10-15
   
a  =  atto  =  10-18
   z =  zepto  =  10-21
  y  =  yocto  =  10-24
   

Ion Product for Water
pKw  =  14.3463 at 15 C, 13.9965 at 25 C, 13.5348  at 40 C

Amphiprotic Salts (e.g., for NaHA):  [H+]  =  [(Ka2CNaHA + Kw) / (1 + CNaHA /Ka1)]½ 

Debye-Huckel Theory
Debye-Huckel Limiting Law (DHLL):  - log γi  =  A zi2 µ½  =  0.5 zi2 µ½ 
Debye-Huckel Equation (DHE):    - log γi  =  (A zi2 µ½)/(1 + B ao µ½)  =  (0.51 zi2 µ½)/(1 + 0.33 o
µ½) 
 
A = 0.5115, B = 0.3291 on a volume (molar) basis at 298 K
A = 0.5108, B = 0.3286 on a mass (molal) basis at 298 K 


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CONSTANTS, UNITS, AND CONVERSION FACTORS in Analytical Chemistry

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