When to cool the crystallization and cool the hot saturated solution? When will it be crystallized by evaporation?

When to cool the crystallization and cool the hot saturated solution? When will it be crystallized by evaporation?

Solubility is greatly affected by the temperature of the cooling heat saturated solution, so that more crystals are precipitated
Solubility is less affected by temperature when using evaporation crystallization, so less impurities are precipitated

Solubility is greatly affected by the temperature of the cooling heat saturated solution, so that more crystals are precipitated
Solubility is less affected by temperature when using evaporation crystallization, so that the precipitation of impurities less

After evaporation of mg water from a potassium hydroxide solution with a mass fraction of W, the mass fraction becomes exactly 2 W, and the mass concentration of the concentrated solution is? A.mW/28Vmol/L B.mW/56Vmol/L C.mW/112Vmol/L D.mW/Vmol/L After evaporation of mg water from a potassium hydroxide solution with a mass fraction of W, the mass fraction becomes exactly 2 W, and the mass concentration of the concentrated solution is? A.mW/28Vmol/L B.mW/56Vmol/L C.mW/112 Vmol/L D.mW/Vmol/L

A
After the potassium hydroxide solution with a mass fraction of W evaporates mg of water, the mass fraction becomes exactly 2 W, so the mass of the original solution is 2 mg, so the next step is simple.