# R - Gas Constant

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Constant / Last modified by KurtHeckman on 2017/11/16 12:35
"R (Gas Constant)" = 8.3144621 J/"Mol * K"
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Gas constant from the Ideal Gas Law expressed in units of Joules / (moles * Temperature).  However, this constant does not have vCalc Units.

The Gas Constant (R) from the Ideal Gas Law is 8.314462 Joules / (moles • Kelvin).  The gas constant (also known as the molar, universal, or ideal gas constant, denoted by the symbol R or R) is a physical constant which is featured in many fundamental equations in the physical sciences, such as the ideal gas law and the Nernst equation.

Ideal Gas Law: PV = nRT     (Click any Parameter)

• P = n•R•T / V :
• V = n•R•T / P :
• n = (P•V)/(R•T) :
• T = (P•V)/(n•R) :

It is equivalent to the Boltzmann constant, but expressed in units of energy (i.e. the pressure-volume product) per temperature increment per mole (rather than energy per temperature increment per particle). The constant is also a combination of the constants from Boyle's law, Charles's law, Avogadro's law, and Gay-Lussac's law.

The Gas Constant (R) appears in many formulas including the following:

• Activation Energy:  E_a = (R*T_1*T_2)/(T_1 - T_2) ln(k_1/k_2)
• Arrhenius Equation:  k = Ae^(E_a/(RT))
• Barometric Formula (Troposphere): p = p_0*(1 - (L*h)/T_0)^((g*M)/(R*L))
• Compressibility Factor:  Z = (p*V_m)/(R*T)
• Peng-Robinson Equation of State:  p = (R*T)/(V_m - b) - (a*alpha)/(V_m^2 + 2*b*V_m - b^2)
• Reduced Specific Volume:  v_r = v/(R* (T_cr)/P_c)
• Van't Hoff Equation:  ΔH^0 = R * ( -ln(K_2/K_1))/ (1/T_1 - 1/T_2)

#### Reference

• Some descriptive text in the description of the Gas constant comes from Wikipedia:  wikipedia/wiki/Gas_constant