Let S be the solubility of CaSO4. CaSO4⇌Ca2++SO42− [Ca2+]=[SO42−]=S Ksp[Ca2+][SO42−]=S×S=S2=9×10−6 ⇒‌‌S=0.003M The molar mass of CaSO 4 is 40+32+64=136g The solubility in g/L is 0.003×136=0.408g/L means, 0.408g dissolves in 1L. 1g will dissolve in =1/0.408=2.45L