Given that 1g of Phenacetin requires 82mL of hot water to dissolve, or 1310mL of cold water (TY= 3.92g):

Question

1) How much water will you need to recrystallize the theoretical yield?
2) How much product will be lost because of recrystallization?

Answer 1

1) You have 3.92g and 1g will disssolve in 82 mL; therefore,
3.92 x (82/1) = about 321 mL.

2) How much phenacetin will dissolve in 321 mL if 1g dissolves in 1310 cold?
1g x (321/1310) = about 0.25
So you would get back 3.92-025 = ?
I've estimated here and there; you need to go through it with your own figures.