Final answer:
Whiskey strength is measured using proof, which is twice the alcohol by volume (ABV), and percentage, reflecting the volume of ethanol within the total liquid volume. Percentage helps calculate mass or moles of ethanol in alcoholic beverages by using the known density and molar mass of ethanol.
Step-by-step explanation:
The strength of whiskey is measured using proof and percentage. Specifically, the term proof is often used traditionally to describe the alcohol content of spirits. In the United States, proof is exactly twice the alcohol by volume (ABV) percentage. Therefore, 80 proof whiskey would contain 40% ABV. The concept of percentage is used to discuss the concentration of alcohol, indicating the volume of ethanol per volume of the entire liquid. For example, if a whiskey is 50% ethanol by volume, this means that in every 100 mL of whiskey, there are 50 mL of ethanol.
To calculate the mass of alcohol in a given volume of a drink like vodka, or to find out how many moles of ethanol are present in a bottle of wine, you would use this percentage. If the density of ethanol is known (0.789 g/mL at 20°C), the mass of ethanol in grams can be calculated by multiplying the volume of ethanol (in mL) by its density. From there, if you know the molar mass of ethanol (46.06 g/mol), you can calculate the number of moles of ethanol present.