A compound that has one sulphur atom per molecule, contains 17.2% of sulphur by mass.What is the relative molecular mass of this compound?

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1.) Phosphoric acid(HPO4)(aq) + Calcium Hydroxide(Ca(OH)2)(aq) --> ?
I think it yeilds CaPO4 + 2H30.
2.) If you have 3.5 moles of Calcium Hydroxide, how many moles of phosporic acid do you have?