• SI (International System of Units)

    • Mass in kilogram (kg), Length in meter (m), Temperature in Kelvin (K), Number of gram-mole as mole (mol), Time in second (s), and, Force in Newton (N).

    • The unit of temperature is Kelvin, K (the symbol degree is omitted).

    • Units of pressure: SI unit of pressure is Pascal (Pa), which is 1 N/m\(^2\). This is inconveniently a small unit, in comparison with the pressure of earth’s atmosphere (1 atm). \[\text{1 atm = 760 mm Hg = $1.01325\times10^5$ Pa = 1.01325 bar}\]

    • \(\displaystyle \text{Mole} = \frac{\text{mass in gram}}{\text{molecular weight}}\)

  • An ideal gas at pressure (\(P\)) of \(1.01325 \times 10^5\) N/m\(^2\), and temperature (\(T\)) of 273 K occupies a volume (\(V\)) of 22.4 m\(^3\)/kmol.  The value of universal gas constant \(R\) can be obtained from this statement as below: \[  R = \frac{PV}{T} = \frac{(1.01325\times10^5)\times22.4}{273} = 8314 \text{ J/(kmol.K)} \]

  • API gravity express the specific gravity (SG, at 60\(^\circ\)F) of crude oil and liquid petroleum products. API stands for American Petroleum Institute, USA. The measuring scale is calibrated in terms of \(^{\circ}\)API. \[{}^{\circ}\text{API} = \frac{141.5}{\text{SG}} - 131.5\] Oil with the least specific gravity has the highest API gravity. API gravity increases with increasing temperature, while specific gravity decreases with increasing temperature.

  • Atomic Weight of Common Elements:

    H - 1, C - 12, N - 14, O - 16, S - 32, Cl - 35.45, Na - 23, Fe - 55.85, Ca - 40