Question

I need the answer for all of the questions please:) thats for oragnic chemistry lab

What extra chemical process, accomplished either via enzymes of chemical methods, must occur before the sugars in corn, potatoes, or grass can be fermented by yeast? What is happening during the fermentation process? Describe the set-up in the lab for the fermentation process. What is the difference in boiling point between water and ethanol? How does this affect the choice of distillation (simple versus fractional) that will be used to isolate the ethanol? What is the reason why 100% pure ethanol cannot be isolated? What is the theory behind why this happens with some miscible liquid mixtures and not others?

Answer 1

Fermentations are the chemical processes in which the molecules of sugar or glucose break down anaerobically. Alcohol and Carbon dioxide gas are the products. Carbon dioxide gas is evolved in the form of foams. In the process, one glucose molecule is converted to two pyruvate molecules, producing two net ATP and two NADH.

Water has higher boiling point than ethanol. The boiling point of Ethanol is 78.5 degree Celcius and of water is 100 degree celcius. This difference exists because water molecules have more extensive hydrogen bonding between themselves whereas ethanol molecules have very less hydrogen bonding between them. So less energy is required to vapourise ethanol than water and water has a higher boiling point than ethanol.

Simple distillation is done between those liquids which have very huge difference in their boiling points as in simple distillation, the lioquid is vapourised and condensed once. Water and ethanol have very less difference in their boiling points. So, Fractional distillation is a better choice for isolating ethanol from the mixture, than simple distillation.

100% pure ethanol can not be isolated because water and ethanol form azeotropic solution with ethanol at a concetration of 95% by volume. In an azeotrope, the vapour and the solution exist with same composition. So no further separation occurs.