How many grams of ethanol, CH3CH2OH, should you dissolve in water to make 0.800 L of vodka (which is an aqueous solution that is 6.86 M ethanol)?

252.5g

Explanation:

Given parameters:

Volume of vodka = 0.8L

Molarity of ethanol  = 6.86M

Unknown:

Mass of ethanol  = ?

Solution:

Molarity is one of the ways of expressing concentration. It is the number of moles of a substance in a solution.

 Since Vodka = ethanol + water  = solution

    Molarity  =

    Number of moles of ethanol  = molarity of vodka x volume of solution

Once we obtain the number of moles, we can derive the mass of the ethanol;

 Number of moles  = 6.86M x 0.8L  = 5.49moles

Mass of ethanol  = number of moles x molar mass

molar mass of ethanol   = 12 + 3(1) + 12 + 2(1) + 16 + 1 = 46g/mol

  Mass of ethanol  = 5.49 x 46 = 252.5g