In the reaction between ethanol and oxygen, which element is reduced and which element is oxidized, and why?

The balanced chemical reaction between oxygen and ethanol can be written as:

`C_2H_5OH + 3O_2 -> 2CO_2 + 3H_2O`

Here, 1 mole of ethanol reacts with 3 moles of oxygen to generate 2 moles of carbon dioxide and 3 moles of water. 

To determine which element has been reduced and which has been oxidized here, we need to calculate the oxidation number of each element in this reaction. The element which has lost electrons is termed "oxidized" and the one which has gained electrons will be term "reduced". 

The oxidation number of carbon in ethanol is

= 1/2 x (0 - 6 x 1 + 2) = -2

and in carbon dioxide = 0 - 2 x (-2) = 4

Thus, carbon has lost 6 electrons and is the element that has been oxidized.

The oxidation number of oxygen in oxygen gas is 0 and in water or carbon dioxide, it is -2. Thus, oxygen has gained 2 electrons and is the element that has reduced. 

Therefore, carbon is oxidized and oxygen is reduced in the reaction between ethanol and oxygen.

Hope this helps.