( ( ( Impedes formation ) ( of sulfur ) ) ( trioxide . ) )
(ROOT (S (NP (NP (JJ Impedes) (NN formation)) (PP (IN of) (NP (NN sulfur)))) (VP (VBP trioxide)) (. .)))
Impedes formation of sulfur trioxide.
(ROOT (S (NP (NNP Sulfur)) (VP (MD can) (VP (VB combine) (PP (IN with) (NP (NN oxygen))) (S (VP (TO to) (VP (VB produce) (NP (NN sulfur) (NN trioxide))))))) (. .)))