Is your representations a list ? Then you can only have that as the single create statement.
I assume Neo4j 1.9 from your syntax.
What you can do though is to use FOREACH
START stack=node({stack})
CREATE (item {item})
CREATE (stack)-[:Item]->(item)
FOREACH (r in {representations} :
CREATE (representation {r}), (item)-[:Representation]->(representation)
)
MATCH (item)-[:Representation]->(representations)
RETURN item, representations