A tank holds 10,000 kg solution of Na2CO3 at 30 degrees celsius. you want to crystalllize from this solution 3000 kg of Na2CO3H2O without any accompanying water. to wha temperature must the solution be cooled? Below is the solubility table for Na2CO3

Question

anonymous · Answer

Temp             Solubility (g Na2CO3/100 g H20)
0                    7
10                  12.5
20                  21.5
30                  38.8

cuanchi · Answer

do you want to crystallize Na2CO3 or Na2CO3H2O ? the solubility table is for Na2CO3.
According to my calculations your 10,000kg of solution can have a maximum of 2795 kg of Na2CO3 in solution at 30C. 
Remember the solubility is g of solute in 100 g of solvent (no in g of solution) to calculate you have to add the g of solute plus the g of solvent. That's means 

38.8g of Na2CO3 in 138.8g of solution
38.8kg of Na2CO3 in 138.8kg of solution

10000 kg of solution x 38.8 kg of Na2CO3 /138.8 kg of solution = 2795 kg of Na2CO3 

Will be impossible to get 3000kg even if you evaporate all the water