A question that's "impossible to answer in a vacuum" is one which (1) lacks foundational context (e.g. experience, resources, etc.) or (2) uses subjective comparisons (e.g. "is X hard").
A question that's "impossible to answer in a vacuum" is one which (1) lacks foundational context (e.g. experience, resources, etc.) or (2) uses subjective comparisons (e.g. "is X hard").