1 / 16

Calculations Involving Colligative Properties

Calculations Involving Colligative Properties. Review. Molarity (M) = moles of solute liter of solution Dilutions: M 1 x V 1 = M 2 x V 2 Percent by volume (%(v/v)) = volume of solute x 100% volume of solution

hank
Download Presentation

Calculations Involving Colligative Properties

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Calculations Involving Colligative Properties

  2. Review Molarity (M) = moles of solute liter of solution Dilutions: M1x V1= M2x V2 Percent by volume (%(v/v)) = volume of solute x 100% volume of solution Percent by mass (%(m/m)) = mass of solute x 100% mass of solution

  3. Review • Colligative Property: A property that depends only upon the solute concentration and not on the solute’s identity. • Four Important Colligative Properties of Solutions. • Vapor-pressure lowering • Boiling-point elevation • Freezing-point depression • Vapor Pressure Molarity (M) = moles of solute liter of solution Molality (m) = moles of solute_ kilogram of solvent • Molality is the number of moles of solute dissolved in 1 kilogram (1000 g) of solvent.

  4. Mole Fraction (another way to express concentration) Mole Fraction: the ratio of the moles of the solute to the total number of moles of solvent and solute. XA= nA___ XB= nB___ nA + nB nA + nB

  5. Freezing-Point Depression & Boiling-Point Elevation

  6. Freezing-Point Depression ∆Tf = Kfm i • ∆Tf = Freezing Point Depression • Difference between the freezing point of the solution and the freezing point of pure solvent • Kf = Molal Freezing Point Depression Constant • Equals to the change in freezing point for a 1-molal solution of a nonvolatile molecule solid • Values are listed in a table • Depends upon the solvent • Units (°C/m) • m = Molal Concentration • i = Number of Ions from each formula unit

  7. Freezing Point Depression

  8. Applications salting icy roads making ice cream antifreeze cars (-64°C to 136°C) fish & insects

  9. Boiling-Point Elevation ∆Tb = Kbm i • ∆Tb = Boiling-Point Elevation • Difference between the boiling point of the solution and the boiling point of pure solvent • Kb = Molal Boiling Point Elevation Constant • Equals to the change in boiling point for a 1-molal solution of a nonvolatile molecule solid • Values are listed in a table • Depends upon the solvent • Units (°C/m) • m = Molal Concentration • i = Number of Ions from each formula unit

  10. Solution Calculations • What is the molarity of a 1.11 ppm solution of Zn2+ ions?

  11. How Vapor Pressure Depression Occurs • Solute particles take up space in a solution. • Solute particles on surface decrease # of solvent particles on the surface. • Less solvent particles can evaporate which lowers the vapor pressure of a liquid.

  12. Vapor Pressures of Pure Water and a Water Solution The vapor pressure of water over pure water is greater than the vapor pressure of water over an aqueous solution containing a nonvolatile solute. Solute particles take up surface area and lower the vapor pressure

  13. Raoult’s Law • Vapor pressure of a solution varies directly as the mole fraction of solvent Vapor PressureSolution = (molefractionsolvent)(Vapor Pressuresolvent)

  14. Solid Calculations • Chemical analysis showed 1.23 mg Fe in a 15.67 g sample of soil. • What is the Fe concentration in ppm?

  15. Unusual concentration units • How many nano moles of Cu are present in 12.3 µL of 25 ppm CuSO4?

More Related