The standard @E02141@ of @A00093@ \(\Delta ^{\ddagger}H^{\,\unicode{x26ac}}\) is the @E02141@ change that appears in the thermodynamic form of the rate equation obtained from conventional @T06470@. This equation is only correct for a first order reaction, for which the @R05138@ has the dimension reciprocal time. For a second order reaction, for which the @R05138@ has the dimension (reciprocal time) × (reciprocal concentration), the left hand side should be read as \(k\ c^{\,\unicode{x26ac}}\), where \(c^{\,\unicode{x26ac}}\) denotes the @S05909@ (usually \(\pu{1 mol dm-3}\)). \[k = \frac{k_{\text{B}}\ T}{h}\ \text{e}^{\frac{\Delta ^{\ddagger }S^{\,\unicode{x26ac}}}{R}}\ \mathrm{e}^{\frac{-\Delta ^{\ddagger }H^{\,\unicode{x26ac}}}{R\ T}}\] The quantity \(\Delta ^{\ddagger}S^{\,\unicode{x26ac}}\) is the standard @E02150@, and care must be taken with standard states. In this equation \(k_{\text{B}}\) is the @B00695@, \(T\) the absolute temperature, \(h\) the @P04685@, and \(R\) the @G02579@. The @E02141@ of @A00093@ is approximately equal to the @A00102@; the conversion of one into the other depends on the @M03989@. The @E02141@ of @A00093@ is always the standard quantity, although the word standard and the superscript \(^{\circ}\) on the symbol are often omitted. The symbol is frequently (but incorrectly) written \(\Delta H^{\ddagger }\), where the standard symbol is omitted and the \(\ddagger \) is placed after the \(H\).