Question: What is the excipient with the lowest pKa whose has part is hydrogen ?
Paraphrase: Which excipient with the lowest pKa is partly hydrogen
SPARQL (Wikidata): select ?ent where { ?ent wdt:P31 wd:Q902638 . ?ent wdt:P1117 ?obj . ?ent wdt:P527 wd:Q556} ORDER BY ASC(?obj)LIMIT 5 
Answer: benzoic acid, acetone