Ratio of molar mass 2 component ideal solution

[sandra]

Homework Statement

Component 1 and 2 form an ideal solution. The vapor pressure of pure component 1 is 13.3kPa at 298K, and the corresponding vapor pressure of component 2 is approximately zero. If the addition of 1.00 g of component 2 to 10.0g of component 1 reduces the total vapor pressure to 12.6 kPa, find the ratio of the molar mass of component 2 to that of component 1.

Homework Equations

x₁ = p/p*
x₁ = n₁/(n₁+n₂)
n₂=n₁(1/x₁-1)

The Attempt at a Solution

x₁ = p/p* = 12.6/13.3 = 0.947
Mass of component 1 = m₁
n₁ = 10g/m₁
x₁ = n₁/(n₁+n₂)
n₁+n₂= n₁/x₁
n₂=n₁(1/x₁-1)
=10/m₁(1/0.947 - 1) = 0.5597/m₁
m₂=1/(0.5597/m₁) = m₁/0.5597
m₁/m₂ = 0.5597
Can anybody tell me if this looks right? thank you

 

[Borek]

Close. Have you used rounded down 0.947 for calculations? You should not round down intermediate results.

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[sandra]

If I don't round I get m₁/m₂=0.5556
Is that right? Thanks!

 

[Borek]

Watch significant digits.

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methods