Yes, SOLUBILITY is a Scrabble word!

Letter values in Scrabble US: S 1, O 1, L 1, U 1, B 3, I 1, L 1, I 1, T 1, Y 4.

Is it a valid word?

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

the quantity of a particular substance that can dissolve in a particular solvent (yielding a saturated solution)
the property (of a problem or difficulty) that makes it possible to solve
the quality of being soluble and easily dissolved in liquid