To??a??mixture??of??5-methyl??salicylaldehyde??(5??g,??16.5??mmol),paraformaldehyde (1.43 g, 48.64 mmol) and concd HCl (25 mL)were added, followed by concd H 2 SO 4??(5–6 drops). The solutionwas refluxed for 2 h and then HCl gas was passed through the reac-tion mixture, which was then refluxed for another 2 h.问题一：5-methyl??salicylaldehyde??分子量：136.15。怎么算出的(5??g,??16.5??mmol)？问题二： and then HCl gas was passed through the reaction mixture这句话的意思不明白
