Using ethanol’s density of 0.789 g/mL, calculate the molarity of ethanol in a beer marked as 5.6%

alcohol. (Hint: 5.6% means 5.6mL of ethanol for every 100mL of solution)

So I know the formula for Molarity is Number of Moles/ Liters of Solution, however I'm confused on how to apply it, or even if it is applied to solve this question. Any help is deeply appreciated.

Mary

1 answer

If you have 5.6 mL ethanol in 100 mL solution, then you have 56 mLethanol in 1 L of solution.
How many grams is that? mass = volume x density = 56 x 0.789 = ? grams ethanol. How many moles is that? That's
mols = grams/molar mass. You have grams and you have molar mass. Solve for mols
Then M = mols/L solutiion and you have it.