The equilibrium between hydrogen cyanide (HCN) and its isomer hydrogen isocyanide (HNC) is important in interstellar chemistry:

HCN (g) ‡„ HNC (g)

A long-standing €œpuzzle€ regarding this reaction is that in space (T = 2.75 K) surprisingly large amounts of HNC are observed. For example, HNC/HCN ratios approaching 20% have been observed in comets (Advances in Space Research, 31 [2003]: 2557). Using the spectroscopic information provided below and knowledge that the potential-energy surface minimum of HNC lies roughly 5200 cm^ˆ’1 higher in energy relative to HCN, calculate the theoretical value for K_P for this reaction occurring in interstellar space.

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ň (cm-) 2041 2024 v: (cm-1) 712 464 B (cm-1) 1.477 M (g mol-) 27.03 27.03 V3 (cm-1) 3669 3653 HCN HNC 1.512