Georgia Performance Standard SC7: Students will characterize the properties that describe solutions and the nature of acids and

bases.

•Triatomic

•Covalent

•Polar bonds & polar overall

•Bent at 105° angle

Intermolecular ForcesPolar molecules

are attracted to one another by dipole forces

Water is attracted to other water molecules by a special dipole force, a hydrogen bond

Water Solutions“Chemically pure water never exists in

nature because water dissolves so many substances.” textbook

Universal solventAqueous solutions

Water SolutionsIonic compounds

most readily dissolve in water due to extreme polarity

Polar covalent compounds also dissolve in water

Nonpolar compounds don’t

Solvation of Ionic Compounds

A Few Exceptions...Remember the

solubility rules...In some ionic

compounds, the ions are so attracted to each other that they won’t break apart and dissolve.

These are INSOLUBLE ionic compounds.

Solvation of Covalent CompoundsCovalent compounds do NOT break apart in

water when dissolving.Solvation of covalent compounds means that

each solute molecule is surrounded by water molecules.

ConductorsIn general,

aqueous solutions of ionic compounds are electrolytes.

Generally, aqueous solutions of covalent compounds are nonelectrolytes.

Solution VocabularySolute: Dissolves in the solvent

Soluble: Able to be dissolved in the solvent (applicable to any states of matter)

Insoluble: Unable to be dissolved in the solvent (applicable to any states of matter)

Miscible: Able to be dissolved in the solvent (applicable to liquid/liquid solutions)

Immiscible: Unable to be dissolved in the solvent (applicable to liquid/liquid solutions)

Solubility VocabUnsaturated: less than maximum

amount of solute is dissolved in the solvent

Saturated: maximum amount of solute is dissolved in the solvent

Supersaturated: special conditions have been created to dissolve more than maximum amount of solute in the solvent

Determines IF Solute Will Dissolve...The nature of the solvent and solute

governs whether a solute will solvate in a particular solvent. Specifically, the nature of the intramolecular bond. Polar molecules will solvate with polar molecules. Nonpolar molecules will solvate with nonpolar molecules. BUT, polar and nonpolar will not form solutions together.

Determines Speed of Dissolving

1. Agitation: Create more collisions mechanically

2. Temperature: More kinetic energy creates more collisions

3. Surface Area: Dissolving process is a surface phenomenon, the more surface of the solute that is exposed the faster the solvation

BRING SOLUTE IN CONTACT WITH SOLVENT

Determines How Much Will Dissolve

1. Temperature: solubility of solid solute increases as the temp. increases; solubility of gaseous solute decreases as temp increases ex. Hot water bubbles, thermal pollution

2. Pressure: solubility of gaseous solute increases as the pressure increases

-Henry’s Law ex. Soft drinks

SOLUBILITY: HOW MUCH WILL DISSOLVE

Temperature & SolubilityHigher the

temperature, the more solid will dissolve in a liquid

Higher the temperature, the less gas will dissolve in a liquid

Henry’s Law: Pressure & Solubility

At a given temperature, the solubility of a gas is proportional to the pressure of the gas above the liquid.

Page 506

The higher the pressure, the more carbon dioxide will dissolve in the syrup giving a less “flat” taste.

Solubility Graph

Concentration of SolutionsThe concentration of a solution is a measure of

how much solute is dissolved in a specific amount of solvent or solution.

Molarity: most common units of solution concentration; # of moles solute dissolved in one liter of the solution

Molarity: moles of solute liter of solution

If given grams, remember to change it to moles.

Example 15.3 (page 531)

Calculate the molarity of a solution prepared by dissolving 11.5 g of solid NaOH in enough water to make 1.50L of solution.

Example 15.4 (page 532)

Calculate the molarity of a solution prepared by dissolving 1.56 g of gaseous HCl into enough water to make 26.8 mL of solution.

molality: moles of solute kg of solvent

If given grams, remember to change it to moles.

The most common concentration term in chemistry is Molarity (M),

but chemists also report concentration in molality (m)

sometimes.

The front of the last page in the calculations packet refers to Molality. Complete 1 (a), 2 (a), 3 (b), and 4 (b).

NOTE: Questions 3 and 4 will require you to manipulate the equation. Question 4 might even require that you change the units of your answer at the end of the calculation.

Preparing a Solution in the LabYou’ve learned about concentration (Molarity

and molality). Therefore, you should be able to create your own solutions for use in the lab from now on.Example:

0.5 M HCl reacts with Mg(s) If I gave you HCl powder, what would you do to make

the solution? Watch these kids, and assess your plan. Choose a lab group and station. Draw an assignment

from the cup, and make the solution. Write your steps (including materials) as you go.

ALSO: Solve 15-2 Practice Problems WS 6, 8, 10-12, 14-16.

Diluting SolutionsIf you already have a solution molarity, but you

want a different molarity:Example: Your lab asks you to use 250 mL of 0.25M HCl, but you only find a jug of 6M HCl in the stockroom.

USE THIS EQUATION: M1V1 = M2V2

Example 15.8 (page 539)

What volume of 16 M sulfuric acid must be used to prepare 1.5 L of a 0.10 M H2SO4 solution?

*Be sure to solve the Dilution Worksheet in your practice packet!

Using Molarity as a Conversion FactorYou have learned to calculate molarity using

the equation: Molarity = moles of solute / liter of solution

Did you realize that the calculation is simply a ratio of solute to solution?

Ratios (ie mole ratios, energy to mole ratios) can be used as conversion factors in stoichiometry.

THEREFORE, molarity can be written into our dimensional analysis charts to solve stoichiometry problems.

Solutions StoichiometryWhat volume of 1.5 M HCl is needed to react with

21.5 grams of NaOH?What is the molarity of a solution of H2S if 48.5mL

are required to titrate 35.6mL of 0.35M Fe(OH)3 solution?

A white precipitate forms when 200 mL of 0.200M K3PO4 solution is mixed with 300 mL of 0.250 M CaCl2 solution. What mass of precipitate will form?

BE SURE TO SOLVE THE PRACTICE PROBLEMS IN YOUR PACKET!

Physical properties of solution are different from the physical properties of the solvent. Some properties are different simply because there are “foreign” particles (solute) in the solvent. Colligative properties of solutions depend only on the number of solute particles.

Boiling Point ElevationMore solute particles means that vapor

pressure is lower which means that more kinetic energy is needed to make vapor pressure equal atmospheric pressure!

Change in temperature is calculated:∆Tb = Kb m i

Since boiling point increases...ADD the change.

Kb will be given.

Freezing Point DepressionLiquid particles get into an orderly

pattern to become a solid. The solute particles disrupt the orderly pattern causing more kinetic energy to be drawn from the solution for it to freeze!∆Tf = Kf m i

Since freezing point decreases...SUBTRACT the change. Kf will be given

About.com Chemistry Ice has to absorb energy in order to melt, changing the

phase of water from a solid to a liquid. When you use ice to cool the ingredients for ice cream, the energy is absorbed from the ingredients and from the outside environment (like your hands, if you are holding the baggie of ice!). When you add salt to the ice, it lowers the freezing point of the ice, so even more energy has to be absorbed from the environment in order for the ice to melt. This makes the ice colder than it was before, which is how your ice cream freezes. Ideally, you would make your ice cream using 'ice cream salt', which is just salt sold as large crystals instead of the small crystals you see in table salt. The larger crystals take more time to dissolve in the water around the ice, which allows for even cooling of the ice cream.

MolalityAnother unit for concentrationm=moles of solute per kilogram of solventpage 520

Solutions StoichiometryA white precipitate forms when 200 mL of

0.200M K3PO4 solution is mixed with 300 mL of 0.250 M CaCl2 solution. What mass of precipitate will form?

What volume of 1.5 M HCl is needed to react with 21.5 grams of NaOH?

What is the molarity of a solution of H2S if 48.5mL are required to titrate 35.6mL of 0.35M Fe(OH)3 solution?