4th Quarter: Colligative Properties of Solutions

COLLIGATIVE PROPERTIES OF SOLUTIONS

1.    Colligative Properties depend on the concentration of solute in solvent and not upon the identity of the solute.

a.    Vapor pressure reduction is a colligative property in which the pressure of the vapor over a solvent is reduced when a nonvolatile solute dissolved in the solvent.  It is directly proportional to the concentration of a solution.

b.    Boiling Point Elevation is a colligative property in which the boiling point of a solvent is raised when a nonvolatile solute is dissolved in the solvent.  It is directly proportional to the concentration of a solution.

c.    Freezing point depression is a colligative property in which the freezing point of a solvent is lowered by the addition of a solute.

d.    Osmotic pressure is the force that makes osmosis possible.

2.    The gas pressure resulting from the vapor molecules over the liquid is the vapor pressure.

3.    Boiling Point is the temperature at which the vapor pressure of a liquid becomes equal to the atmospheric pressure.

4.    Osmosis refers to the movement of solvent through a semi permeable membrane from a region of higher concentration to a region of lower concentration.

5.    The most commonly used measurements of concentration are molarity, molality and mole fraction.

Boiling Point elevation	Freezing Point Depression
Tb= Kbm Where: Tb= boiling point elevation (oC)           Kb= molal boiling point elevation constant of solvent (oC/m) m= molality (m)	Tf= Kfm Where: Tf= freezing point depression (oC) Kb= molal boiling point elevation constant of solvent (oC/m) m= molality (m)

Vapor pressure Reduction	Osmotic pressure
Pa= XaPoa Where: Pa= vapor pressure lowering of solution Xa=  mole fraction of solute Poa=  vapor pressure of pure solvent Units of pressure: mmHg, atm, Pa, torr,	π=MRT Where:   ¶=  osmotic pressure in atm                M=        Molarity (mol/L)                R= 0.0821 L atm/mol K                T=  temperature in Kelvin         K=  oC + 273

4th Quarter: Concentration of Solutions

Concentration Review Worksheet

1)         If I make a solution by adding 83 grams of sodium hydroxide to 750 mL of water…

a)         What is the molality of sodium hydroxide in this solution?

          

b)         What is the percent by mass of sodium hydroxide in this solution?

c)         What is the mole fraction of sodium hydroxide in this solution?

2)         If I make a solution by adding water to 35 mL of methanol (CH₃OH) until the final volume of the solution is 275 mL…

a)         What is the molarity of methanol in this solution? (The density of

            methanol is 0.792 g/mL)

b)         What is the percent by volume of methanol in this solution?

Concentration Review Worksheet Answers

1)         If I make a solution by adding 83 grams of sodium hydroxide to 750 mL of water…

            To solve problem 1, you need to have calculated for various parts that there are 2.08 moles of NaOH (which has a molar mass of 40 g/mol), that there are 750 grams of water (which has a density of 1 g/mL), and that there are 41.67 moles of water (which has a molar mass of 18 g/mol).

a)         What is the molality of sodium hydroxide in this solution?

                        2.77 m (2.08 mol / 0.75 kg water)

b)         What is the percent by mass of sodium hydroxide in this solution?

                        9.96% (found by finding 83 g / 833 g and multiplying by 100%)

c)         What is the mole fraction of sodium hydroxide in this solution?

                        0.0475  (found by finding 2.08 mol / 43.75 mol)

2)         If I make a solution by adding water to 35 mL of methanol (CH₃OH) until the final volume of the solution is 275 mL…

            When solving this problem, you’ll need to calculate that there are 27.72 grams of methanol (from the density), which is equal to 0.866 mol.        

a)         What is the molarity of methanol in this solution? (The density of

            methanol is 0.792 g/mL)

                        3.15 M (0.866 mol/0.275 L)

b)         What is the percent by volume of methanol in this solution?

            12.7% ( (35 mL/275 mL)  X 100)

Science Investigatory Project S.O.S.

Hi there students.


Here's a sample of how research papers should look like. I'll be posting some more to help you with your project... hope this would somehow help you.


https://docs.google.com/viewer?a=v&q=cache:OT0IyASQt2UJ:www.modernghana.com/GhanaHome/download.asp%3Fid%3D102+chapter+1+introduction+background+of+the+study&hl=en&pid=bl&srcid=ADGEESg-G_177wxow-ehIdpkvPbigb8moybivucqYYdpm-SvD2EQd0lDSr6hMNvAdUujWerityqJGTu4LgCPNvoByuEN3ing13RIIosofSCg3x01ZiFE5k2rOhpaIj7_sXhM46vBCdJj&sig=AHIEtbQtqRSgfQnjP0gmJ5ZGsZgAahGgow