English Vocabulary Flash Cards - Chemical Formulas @ englishpdf.com and englishteststore.com File 122 GeO germanium(II) oxide HBr hydrogen bromide or hydrobromic acid HCCH acetylene or ethylene HCN hydrocyanic acid or hydrogen cyanide HCONH2 formamide or methanamide HCOO− formate ion HCOOH formic acid or methanoic acid HCOONH4 ammonium formate