The molarity of H3PO4(d=1.8g/mL) is 18 M. Hence, mass percentage and molality are:

Density = 1.8 g/mLMolarity = 18 M = 18 mol H3PO4 in 1 L solution1000 mL solution has H3PO4= 18 mol = 18 × 98 g100 mL = (1800 g) solution has H3PO4 = 18 × 98 gH3PO4 by mass o/o (by weight of solution) =18×981800×100=98%or (1800−18×98)gH2O (solvent) H3PO4=18×98g2g solvent has H3PO4=98g=1molH3PO41g=1000g solvent has H3PO4=500 molal Thus, 98%, 500 molal.