If 17.5 moles of ethanol were produced, how many moles of glucose were there in the beginning?

The reaction is (Ignoring the state symbols)

This equation tells us that for every 2 molecules of ethanol, there is one mole of glucose.

So there is 17.5 / 2 moles of glucose in the beginning, which is 8.75 moles.

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.