During fractional distillation of ethanol / water mixture, why can’t pure ethanol be obtained (i.e. distillated contains a little water)?

During fractional distillation of ethanol-water mixture, it is not possible to obtain pure ethanol because ethanol and water form an azeotropic mixture, which is a mixture that has a constant boiling point and composition throughout the distillation process. This means that when the mixture is heated, both ethanol and water evaporate together, and the resulting vapor has the same composition as the original mixture. This makes it impossible to obtain pure ethanol by simple distillation. The azeotropic point of the ethanol-water mixture is about 95% ethanol and 5% water. This means that if the mixture is distilled to an extent where the concentration of ethanol reaches 95%, further distillation does not lead to a significant increase in ethanol concentration. Instead, the remaining distillate will still contain about 5% water. To obtain pure ethanol from the mixture, other methods such as molecular sieves, dehydration agents, or rectification can be used. These methods involve using chemical reactions or additional separation techniques to remove the remaining water from the distillate and obtain pure ethanol.