[Pirulli Chemistry] Name: ____________________________________________ Per: ________ Date:2/27/20

Colligative Properties & Table H

Do Now: How many grams of C6H12O6 are needed to be dissolved in water to make 100. grams of a 250. ppm solution?

Molecular vs. Ionic Compounds in Aqueous Solutions

● Molecular compounds dissolve but do not dissociate into ions.

= ___________________________

C6H12O6(s) (glucose) → C6H12O6 (aq)

__________ of sugar gives __________ of sugar when dissolved in water

● Many ionic compounds dissociate into independent ions when dissolved in water

=______________________ _____________________________

NaCl (s) → Na+(aq) + Cl-(aq)

_______ of solid NaCl gives _______ of sodium ions and _______ of chloride

ions when dissolved (total of _______ of dissolved particles).

K2S (s) → 2K+(aq) + S-2(aq) (Total of __________ of dissolved particles)

Dissociation of Ionic Compound with Polyatomic Ions Polyatomic ions remain INTACT →

1. 1 mole of KCl (s) = ____ moles of ions in an aqueous solution

2. 1 mole of K2SO4 (s) = ____ moles of ions in an aqueous solution

3. 1 mole of K3PO4 (s) = ____ moles of ions in an aqueous solution

4. 1 mole of KNO3 (s) = ____ moles of ions in an aqueous solution

Colligative Properties

● Colligative properties refer to properties of a solution that depend on the ________________________________.

o BOILING POINT, FREEZING POINT & VAPOR PRESSURE.

Boiling Point Elevation

● The presence of a _________________________ (salt or sugar) _______________ the boiling point of the

solvent. (Nonvolatile: does not easily vaporize)

● The ______________ the concentration (more moles of dissolved particles) of the solute, the more it _________

the boiling point. (This is where the number of moles given when a substance is dissolved from the beginning is important.)

Example:

5. Which sample, when dissolved in 1.0 liter of water, produces a solution with the highest boiling point?

a. 1 mole KI

b. 2 mole KI

c. 1 mole MgCl2

d. 2 mole MgCl2

EXPLANATION:

6. Which solution has the highest boiling point?

a. 10 g of KI dissolved in 100 g of water

b. 20 g of KI dissolved in 200 g of water

c. 30 g of KI dissolved in 100 g of water

d. 40 g of KI dissolved in 200 g of water

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Freezing Point Depression

● The presence of a nonvolatile solute (salt or sugar) _______________ the freezing point of the solvent.

● The ____________ the concentration (more moles of dissolved particles) of the solute, the more it ____________ the freezing point.

Example:

7. Which sample, when dissolved in 1.0 liter of water, produces a solution with the lowest freezing point?

a. 1 mole KI

b. 2 mole KI

c. 1 mole MgCl2

d. 2 mole MgCl2

EXPLANATION:

What is Vapor Pressure?

Vapor: Vapor Pressure:

Vapor Pressure Lowering

● The presence of a nonvolatile solute (salt or sugar) _______________ the vapor pressure of the solvent.

● The ____________ the concentration (more moles of dissolved particles) of the solute, the more it ____________ the vapor pressure.

Summary: Bringing it all together with intermolecular forces IMF determine how strongly the molecules are held together.

London Forces Dipole-Dipole Interactions Ion-Dipole Interactions Hydrogen Bonding

Weak IMF → The molecules aren’t held together so tightly, so it's pretty easy for them to leave the liquid to become a gas.

_______ IMF =

_______ vapor pressure =

_______ boiling point

Strong IMF → The molecules are held together tightly, so it takes more energy for them to leave the liquid to become a gas.

_______ IMF =

_______ vapor pressure =

_______ boiling point

● Adding a solute weakens the intermolecular forces between the molecules in the solvent. ○ Think about having a really strong bond with a friend, and the bond is weakened when your friend begins to date

someone because there is someone between you and your friend. On your own:

8. How are the boiling and freezing point of a sample of water affected when a salt is dissolved in the water?

a. BP decreases/ FP decreases

b. BP decreases/ FP increase

c. BP increases/ FP decreases

d. BP increases/ FP increases

EXPLANATION:

9. Which solution containing 1 mole of solute dissolved in 100 grams of water has the lowest freezing point?

a. KOH (aq) b. C6H12O6 (aq)

c. C2H5OH (aq) d. C12H12O11 (aq)

10. Which solution has the highest boiling point at standard pressure?

a. 0.10M KCl (aq) b. 0.10M K2SO4 (aq)

c. 0.10M K3PO4 (aq) d. 0.10M KNO3 (aq)

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More about vapor pressure → Table H(page 4 of your reference table)

● This table shows the vapor pressure, in kPa, of four liquids as a function of _______________.

When the vapor pressure of water is 30 kPa, the temperature of the water is

a. 20°C b. 40°C c. 70°C d. 100°C

Which graph best represents the variation in vapor pressure of water as temperature changes?

● The vapor pressure _____________________________________________ of liquid.

Which sample of water has the greatest vapor pressure?

a. 100 ml at 20°C b. 200 ml at 25°C c. 40 ml at 35°C d. 20 ml at 30°C

EXPLANATION:

● The boiling point of a liquid is the temperature at which the vapor pressure is equal to the atmospheric pressure on the surface

of the liquid. ○ If a temperature-pressure point lies on one of the vapor pressure curves, the liquid is boiling, changing from the liquid to

the gas phase. ● When the atmospheric pressure is equal to standard pressure (101.3 kPa), the boiling point is called the normal boiling point. ● Normal boiling points:

Propanone: °C Ethanol: °C Water: °C Ethanoic acid: °C

The graph below shows the relationship between vapor pressure and temperature for substance X. What is the normal boiling point for substance X?

a. 20°C b. 30°C c. 40°C d. 50°C

EXPLANATION:

● The graph shows that _______________ has the _______________ vapor pressure at any given temperature compared to

the other three liquids (____________ boiling point = ____________ vapor pressure)

● _______________ has the ______________ vapor pressure at any given temperature.

(____________ boiling point = ____________ vapor pressure)

Which liquid has the highest vapor pressure at 65°C?

a. ethanol b. propanone c. water d. ethanoic acid

Which liquid has the lowest vapor pressure at 75°C?

a. ethanol b. propanone c. water d. ethanoic acid

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