What is the vapor pressure at 30 degrees celcuis of a solution of 9.26g of benzene(C6H6,pure liquid vapor...?
A.119 torr
b.375 torr
c.76.3 torr
d.195 torr
Answer:
Treat the liquid mixture as ideal mixture and apply Raoult's law.
It states that the vapor pressure of a mixture equals the sum of pure components vapor pressure times their mole fraction:
p = ∑ x_i · p_i
The number of moles for this binary mixture are:
-benzene
N₁ = m₁ / M₁ = 9.26g / 78.11g/mol = 0.11855mol
-chloroform
N₂ = m₂ / M₂ = 4.26g / 119.38g/mol = 0.03568mol
The molar fractions are
-benzene
x₁ = N₁ / (N₁+ N₂) = 9.26g / 78.11g/mol = 0.7686
-chloroform
x₂ = N₂ / (N₁+ N₂) = 1 - x₁ = 0.2134
The total vapor pressure is
p = x₁ · p₁ + x₂ · p₂ = 0.7686 · 155torr + 0.2134 · 333torr
= 196.2 torr
d is the correct answer
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