Naphthalene a white solid is used in mothballs Assume you ha

Naphthalene, a white solid, is used in mothballs. Assume you have 30.0 g of naphthalene (C₁₀H₈) in 375 g of ethanol, C₂H₅OH. Calculate the molality, molarity, mole fraction and ppm of naphthalene in this solution. The density of ethanol is 0.78 g/mL.

Solution

moles of napthalene =mass/molar mass = 30/128.17 = 0.234,

molality = moles per kg solvent = ( 0.234 x 1000)/( 375) = 0.624 m,

ethanol volume = mass/density = 375 /0.78 = 480.77 ml ,

Molarity = moles per liter solution = (0.234 x1000)/480.77 = 0.4867 M ,

moles of ethanol = 375/46 =8.152,

mol fraction of napthalene = ( 0.234)/(0.234+8.152) = 0.0279,

ppm of napthalene = (30/30+375) x10^ 6 = 74074 ppm