Question

8) Benzene, CsH6, was once used as a common solvent in chemistry. Its use is now restricted because of fear that it might cause cancer. The recommended limit for exposure to benzene is 3.2 milligrams per cubit meter of air ( 3.2 mg/ m3 ) a) Calculate the molarity of the solution in air. b) Calculate the number of parts per million ( mg/ kg) by mass of benzene in the solution. The density of air is 1.29 g/L. ( Clue: What is the solute and what is the solvent?)

Answer 1

GH6 molar mass (M) = 78.11 gm/mol Benzene [CG H6 7 = 3.2 mg/m3 of air . molarity =- mass of Coho X 1 Molar mass x Vair (Leter) [ C6H6] = mass of C6H6 = 302 mg = 3+2X163 g/L 10² L 103 Vair o 1 m3 = 1000L - molarity - 302 x 10-3 x1 78.11 8103 Leter = 0.0409678 x 10-6 = 4.09678 X 10-8 m

(6) = Ppm = . mass of solute mass of solution x 106 " Solute - Solution C6H6 air a mass of air = Vapy x hair = 1000 L x 1.29 gmil - 0290 gm 302 810-3 x 106 Ppm = 1290 = 2048062 PPM