Molarity of Lysol Chemistry

Question

If Lysol Spray (539 grams) has a percent composition of 58% w/w Ethanol, what is the Ethanol's molarity?

Answer 1

58% of what mass = 539 g?

0.58 x = 539 g

x = 929 g

So, the total mass of solution = 929 g and 539 g of that is Lysol.

Mass of ethanol = 929 g - 539 g = 390 g ethanol

To find the molarity we need to know the density of the Lysol/ethanol solution, so we can convert 929 g of solution to mls of solution.

Then we have 390 g ethanol x 1 mol ethanol / 46 g = 8.48 moles ethanol

Then you'd divide 8.48 moles by the volume in liters to obtain molarity.

Answer 2

Begin with defining percent by mass (mass solute/mass solution). Then, use the definition of molarity to figure out what the end result should look like (mol solute/L solution).

(58 g ethanol/100 g solution) x (1 mol ethanol/46.07 g ethanol) x (539 g solution/1 mL solution) x (1000 mL/1L) = 6785.761 M = 6.8 x 10² M [final answer -> rounded to appropriate sig figs]