The sulfur dioxide is oxidized to sulfur trioxide.
ð ə WORD_BOUNDARY s ʌ l f ɜː WORD_BOUNDARY d aɪ ɑ k s aɪ d WORD_BOUNDARY ɪ z WORD_BOUNDARY ɑ k s ɪ d aɪ z d WORD_BOUNDARY t ə WORD_BOUNDARY s ʌ l f ɜː WORD_BOUNDARY t ɹ aɪ ɑ k s aɪ d WORD_BOUNDARY