10. Challenge. Naphthalene is a hydrocarbon with 93.71% carbon by mass. A 0.256-
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Question
10. Challenge. Naphthalene is a hydrocarbon with 93.71% carbon by mass. A 0.256-mol sample has a mass of 32.8 g. Naphthalene works as a pesticide in mothballs by sublimation of the solid so that it fumigates enclosed spaces with its vapors according to the equation: naphthalene(s)naphthalene(g) Kc = 4.29 × 10-6 1 at 298 K. If 3.00 g of solid naphthalene is placed into an enclosed space with a volume of 5.00 L at 25°C, what percentage of the naphthalene will have sublimed once equilibrium has been established?Explanation / Answer
molarity = grams solute/molar mass solute x L of solution
molar concentration of naphthalene in solution = 3 g/128.17 g/mol x 5 L
= 0.0047 M
at equilibrium
ICE chart
naphthalene(s) <===> naphthalene(g)
I 0.0047 -
C -x +x
E 0.0047-x x
--
Kc = [naphthalene(g)]/[naphthalene(s)] = 4.29 x 10^-6
4.29 x 10^-6 = x/(0.0047-x)
2.0163 x 10^-8 - 4.29 x 10^-6x = x
x = 2.0163 x 10^-8/1.00 = 2.1063 x 10^-8 M
Percentage of naphthalene sublimed = (2.0163 x 10^-8 M/0.0047 M) x 100 = 0.00043%
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