Top Posters
Since Sunday
24
10
m
6
t
5
a
5
m
5
J
5
d
5
t
5
r
5
j
5
a
5
New Topic  
Whelan Whelan
wrote...
Posts: 3158
7 years ago
At 80.0°C heptane, C7H16, has a vapor pressure of 428 mm Hg and octane, C8H18, has a vapor pressure of 175 mm Hg. What is the vapor pressure of a solution that contains 20.0 g C7H16 and 11.4 g C8H18?
Textbook 

Introductory Chemistry Essentials


Edition: 5th
Author:
Read 1201 times
10 Replies
Replies
Answer verified by a subject expert
hbutler2hbutler2
wrote...
Top Poster
Posts: 3070
7 years ago Edited: 10 months ago, bio_man
Sign in or Sign up in seconds to unlock everything for free
More solutions for this book are available here
Answer: 344 m Hg

Molar mass of heptane = 100 g/mole

molar mass of octane = 114 g/mole

Thus, moles of heptane in 20g of it = mass/molar mass = 0.2

moles of octane in 11.4 g of it = mass/molar mass = 0.1

Thus, moles fraction of heptane = (moles of heptane/(moles of heptane+moles of octane)) = 0.2/0.3 = 0.67

mole fraction of octane = 1-mole fraction of heptane = 0.33

Now, as per Raoult's Law,

Vapor pressre of solution = P0heptane*mole fraction of heptane + P0octane*mole fraction of ocatne = 344.51 mm Hg
1
I'm a chemical engineer! Slight Smile

Related Topics

wrote...
A year ago
thank you!
wrote...
A year ago
thank you!
wrote...
A year ago
thank you
wrote...
A year ago
thank you
wrote...
A year ago
thank you!
wrote...
A year ago
Thx
wrote...
2 months ago
Thank you
wrote...
2 months ago
Thank you
wrote...
A month ago
Thanks
New Topic      
Explore
Post your homework questions and get free online help from our incredible volunteers
  380 People Browsing
 675 Signed Up Today
Related Images
  
 9431
  
 154
  
 176
Your Opinion
What's your favorite math subject?
Votes: 174