Wine is approximately 12% ethanol (CH3CH2OH) by volume. Ethanol has a molar mass of 46.06 g/mol and a density 0.789 g/mL. How many moles of ethanol are present in a 750-mL bottle of wine?

1.54 moles of pure ethanol are present in 750mL of wine

Explanation:

The sort of concentration 12% by volume, means that in 100 mL of solution (wine) 12 mL are pure ethanol

We use the density of pure ethanol to determine the mass:

Ethanol density = Ethanol mass / Ethanol volume

Ethanol density . Ethanol volume = Ethanol mass

0.789 g/mL . 12 mL = 9.47 g of ethanol

Now we can determine the moles: 9.47 g . 1 mol / 46.06 g = 0.205 moles

Now we can make a rule of three:

In 100 mL of solution (wine) we have 0.205 moles of pure ethanol

Then, in 750 mL of solution we may have (750 mL . 0.205) / 100 = 1.54 moles