Comparison of the emission modeled by MOLLIE (in red, see Sect. 5.1) and the observed emission (in blue) of the H₂CO transition observed at the center of the core. Top panels: results using S16 abundance profile (left panel), and the same scaled by a factor of 220 (right panel). Bottom panels: results using V17 abundance profile (left panel), and the same scaled by a factor of 166 (right panel). The original abundance profiles overestimate the emission of the line by a factor of ~3, and the scaled abundance profiles do not reproduce the shape of the line.