How much does 100 proof alcohol weigh per Gallon?

100 proof alcohol is 50% alcohol and 50% distilled H20. The weight of alcohol is 7 lbs per gallon and the weight of distilled water is 8.34 pounds per gallon. if you mix them 50/50 you should have a final weight of 4.17 + 3.5 = 7.67 pounds:)