Question

The molecular weight of ethanol (CHgCHzOH) is 46 and its density is 0.789 g/cm3. A. \A4rat is the molarity of ethanol in beer that is 5% ethanol by volume? [Alcohol content of beer varies from about 4Vo (lite beer) to B% (stout beer).

Answer 1

Answer:

molarity of ethanol in beer = $\frac{0.086\times 1000}{100}M=0.86M$

Explanation:

5% ethanol in beer by volume means there are 5 mL of ethanol in 100 mL of beer.

Density is the ratio of mass to volume and $1cm^{3}=1mL$

Mass of 5 mL of ethanol = $(0.789\times 5)g=3.945g$

Number of moles is the ratio of mass to molecular weight

So, 5 mL of ethanol = $\frac{3.945}{46}mol$ of ethanol = 0.086 mol of ethanol

Molarity represents number of moles of solute present in 1000 mL of solution.

Here solute is ethanol

So, molarity of ethanol in beer = $\frac{0.086\times 1000}{100}M=0.86M$