What volume of ethanol must be diluted with water to prepare 768 mL of 0.873 M solution? The density of ethanol is given as 0.789 g/mL.

Answer in units of mL

You will require 0.873*0.768 = 0.6705 moles of ethanol. Its molar mass is 46 g/mol, so that is 30.84 g. Divide by the density of ethanol to get the ethanol volume, in ml.