# How many grams of PSO_3H_3 is 0.250 mol?

So you got $\text{thiophosphoric acid....}$, $S = P {\left(O H\right)}_{3}$...
Given that ${n}_{\text{noomber of moles"="mass"/"molar mass}}$..
..then.... $\text{mass"=underbrace(0.250*cancel(mol))_"moles of stuff"xxunderbrace(114.06*g*cancel(mol^-1))_"molar mass of thiophosphoric acid} \equiv 28.52 \cdot g$