{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

10-7-08[lecture10]ec

10-7-08[lecture10]ec - Chem 116 Student Notes(EC Lecture 10...

Info icon This preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Chem 116 Student Notes September 23, 2008 (EC) Lecture 10: Concentrations and Colligative Properties 4 Ways to Express Mixture Density (aka Concentration) • 3 kinds of “particle density” o Molarity (n/V) o o • Useful for stoichiometry calculations Molality (n/m) Useful for boiling/freezing point calculations Mole Fraction (decimal # between 0‐1) Useful for partial pressure calculations 1 kind of “mass density” o Weight Percent (0 – 100%) Useful for chemical analysis of the unknowns “solution” = “mixture” in liquid phase Clicker Question: 1. 2. 3. 4. Solute Na+ and Cl‐ ions Water NaCl (s) Water Solvent Water + ‐ Na and Cl ions Water NaCl (s) (correct) the Na and Cl ions separate (wrong) water = solvent since there is more of it (wrong) NaCl is not in solid form in the solution (wrong) water = solvent since there is more of it In a Solution: 1. BPE: Boiling Point = Higher a. Solute increases the BP of the solvent i. ∆Tbp = i msoluteKbp = (effective molality) (solvent factor) ) (solvent factor given or looked up) =(# of ions) ( =change in boiling temperature caused by the solute 1. Add this number to the Tobp(solvent) b. Solute increase the BP by lowering the vapor pressure (Raoult’s Law) i. Psolvent = Xsolvent Posolvent fraction of surface taken up by solvent = (fraction of surface taken up by solute) (fraction taken up by pure solvent‐1.0) 1. Xsolvent = mole fraction of the solvent 2. Xsolvent + Xsolute1 (+ Xsolute2 + Xsolute3)= 1 ii. This is done by blocking some of the solvent from escaping on the surface iii. For this we have to assume that the solute has no vapor pressure iv. A higher temperature is therefore needed to reach the vapor pressure of the atmosphere (boiling) 2. FPD: Freezing Point = Lower a. Solute decreases the FP of the solvent i. ∆Tfp = i msoluteKfp = (effective molality) (solvent factor) ) (solvent factor given or looked up) =(# of ions) ( =change in freezing temperature caused by the solute 1. Subtract this number to the Tofp(solvent) b. Solute increase the FP by lowering the vapor pressure (Raoult’s Law) i. Psolvent = Xsolvent Posolvent fraction of surface taken up by solvent = (fraction of surface taken up by solute) (fraction taken up by pure solvent‐1.0) 1. Xsolvent = mole fraction of the solvent 2. Xsolvent + Xsolute1 (+ Xsolute2 + Xsolute3)= 1 3. Osmotic Pressure a. (osmotic pressure, π)V = nRT b. c. ...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern