Question

""Three-Two" Beer is 3.2% (ethanol) by WEIGHT. Standard "full strength" beer is typically ~4-5% (ethanol) by VOLUME. Take the density of water to be d(H2O) ~ 1.0 g/mL and the density of ethanol to be d(EtOH) ~ 0.80 g/mL and compare 3.2 and standard on a weight percent or volume percent basis. Show all of your work" I'm honestly not even sure what this question is asking me.

Answer 1

Ans. A [Ethanol] = 3.2 % w/v means that there is 3.2 g ethanol per 100.0 mL of the solution (beer).

#1. 3.2 % w/v Beer:

            Mass of alcohol per 100.0 mL beer = 3.2 g

            Volume of alcohol per 100 mL beer = Mass /Density of alcohol

                                                                        = 3.2 g (0.8 g/ mL)

                                                                        = 4.0 mL

            Volume of water in 100 mL beer = 100 mL – Volume of alcohol

                                                                        = 100 mL – 4.0 mL

                                                                        = 96.0 mL

            Mass of water in 100 mL beer = Volume of water x Density

                                                                        = 96.0 mL x (1.0 g/ mL)

                                                                        = 96.0 g

#2. 4 - 5 % Beer:      let’s proceed with the average value 4.5 % w/v

            Mass of alcohol per 100.0 mL beer = 4.5 g

            Volume of alcohol per 100 mL beer = Mass /Density of alcohol

                                                                        = 4.5 g (0.8 g/ mL)

                                                                        = 5.625 mL

            Volume of water in 100 mL beer = 100 mL – Volume of alcohol

                                                                        = 100 mL – 5.625 mL

                                                                        = 94.375 mL

            Mass of water in 100 mL beer = Volume of water x Density

                                                                        = 94.375 mL x (1.0 g/ mL)

                                                                        = 94.375 g

# Comparison:

            3.2 % w/v beer = 3.2 g or 4.0 mL ethanol per 100 mL beer

            4.5% w/v beer = 4.5 g or 5.625 mL ethanol per 100 mL beer