( ( Carbon dioxide ) ( ( is ( an ( acid gas ) ) ) . ) )
(ROOT (S (NP (NNP Carbon) (NN dioxide)) (VP (VBZ is) (NP (DT an) (JJ acid) (NN gas))) (. .)))
Carbon dioxide is an acid gas.
(ROOT (S (NP (NNP Carbon) (NN dioxide)) (ADVP (RB chemically)) (VP (VBP weather) (NP (NNS rocks)) (PP (IN by) (S (VP (VBG creating) (NP (NNS acids)))))) (. .)))