Q16. Mass balance A mixture of 100 kg is composed from 50 wt% of Na2SO4 and 50 wt% of Na2SO4 -10H20. The solubility chart of Na2SO4 is shown below. Please calculate: (1) how many kg of water is needed to dissolve this solid to form a saturated solution at 20 C? (2) If this solution is cooled down to 10 C, what is the solid product you can obtain? How many kg can you get? (3) If you want to obtain Na2SO4 crystal from this solution (in (1)), what should you do? 60 liquid solution solution + solid Na, 504 50 40 30 T(C) 20 solution solution + - + ice solid Na, 50, -10H, 10 solid Na $02-104,0 + solid Na, 504 ice + eutectic + eutectic -10H solid Na 50 - 10H,0 1 0 10 20 30 40 50 60 70 80 weight fraction Na S04 (%) Figure 1. Phase diagram of Na2SO4-H2O system. 90 100