Learn Swedish: Vems necessär är det här? - Whose toiletry bag is this?

In Swedish, whenever you use a genitive (possessive) word like vems (whose), min (my), or a name with an 's' like Kalles, the noun that follows must be in the indefinite form. Even though we are asking about a specific bag, we must say vems necessär.

Does the phrase vems necessär count as a single unit for the verb-second (V2) rule?

Exactly. The question word vems and the noun it belongs to (necessär) stick together to form the first 'building block' of the sentence. To satisfy the V2 rule, the verb är takes the second position directly after this phrase.

Necessär is an en-word. Why does the sentence end with det här instead of den här?

When you are simply pointing at an object to identify it (like asking 'Whose is this?'), Swedish always uses the neutral pronoun det or det här, regardless of the noun's actual gender. You would only use den här if it were directly attached to the noun, like in the phrase den här necessären (this toiletry bag).

Could I rephrase this sentence as Vems är den här necessären?