The spelling of the chemical formula "PbCHO" can be explained using the International Phonetic Alphabet (IPA). "Pb" represents the element lead, pronounced as /lɛd/. "CHO" represents the functional group of a carbonyl group, pronounced as /kɑrbənoʊl ɡruːp/. Therefore, the correct pronunciation of "PbCHO" would be /lɛd kɑrbənoʊl ɡruːp/. It is important to use the correct spelling and pronunciation of chemical formulas in scientific settings to prevent misunderstandings and ensure accuracy in communication.