Finding Vapor Pressure of Liquid (HW #10.109)

Moderators: Chem_Mod, Chem_Admin

Glenda Marshall DIS 3M
Posts: 68
Joined: Sat Sep 27, 2014 3:00 am

Finding Vapor Pressure of Liquid (HW #10.109)

Postby Glenda Marshall DIS 3M » Sat Feb 07, 2015 5:18 pm

What does it mean to find vapor pressure of a liquid? In problem #10.109 in the homework, part (b) asks "what is the vapor pressure of liquid bromine?" and it does not provide an equation or any other information. It the solutions manual, they solved for K and used that value as the vapor pressure. I don't understand why this is possible. Also part c asks "what is the partial pressure of Br2(g) above the liquid in a bottle of bromine at 25 degrees celsius?" I don't know how this is any different from part (b). Any help would be appreciated! Thanks!

Posts: 18021
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 418 times

Re: Finding Vapor Pressure of Liquid (HW #10.109)

Postby Chem_Mod » Sun Feb 08, 2015 4:22 pm

The vapor pressure is the pressure of a gas that is in equilibrium with its liquid. So if we write the equilibrium expression for Br2 (l) --> Br2 (g), it is just K = [Br2 (g)] because liquids and solids are not included in equilibrium expressions. Therefore, K is exactly the vapor pressure that is asked for.

For part c), the problem wants the partial pressure of monatomic bromine. So you'll use the answer to part a) and solve for [Br (g)] after taking the square root of [Br (g)]^2

Justin Le 2I
Posts: 142
Joined: Fri Sep 26, 2014 2:02 pm

Re: Finding Vapor Pressure of Liquid (HW #10.109)

Postby Justin Le 2I » Wed Feb 11, 2015 1:53 pm

The solutions manual makes this a little confusing because it says PBr(g)^2 but it should actually be without the exponent because we are just solving for the pressure of Br(g)

Return to “Gibbs Free Energy Concepts and Calculations”

Who is online

Users browsing this forum: No registered users and 2 guests