Yes, DISSOCIATED is a Scrabble word!

Letter values in Scrabble US: D 2, I 1, S 1, S 1, O 1, C 3, I 1, A 1, T 1, E 1, D 2.

Is it a valid word?

DISSOCIATED is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

part; cease or break association with
regard as unconnected
to undergo a reversible or temporary breakdown of a molecule into simpler molecules or atoms