Chapter 11- Solutions

Chapter 11- Solutions

• A solution is a homogeneous mixture of two or more substances

• -its particles are evenly distributed• Components of Solutions

a. Solvent- dissolving medium; the larger amountb. Solute- substance dissolved; lesser amount

• Soluble- capable of being dissolved• Insoluble- does not dissolve• Miscible- liquids can dissolve in liquids• Immiscible-liquids that cannot dissolve in other liquids

Types of Solutions

a. Suspension-particles in a solvent are so large that they settle out unless it is stirred or agitated

Example: muddy water, salad dressing

b. Colloids-particles that are intermediate in size between a solution and a suspension

Example: gelatin, fog shaving cream, paints

Solutes

• Electrolyte- substance that dissolves in water that conducts an electric current– Examples: any salt

• Nonelectrolyte- substance that dissolves in water that does not conduct an electric current– Example: sugar

The Solution Process

1. Factors affecting the rate of dissolutiona. Increasing the surface area of the solute- a

solute will dissolve faster if the surface is increasedcrush the solute

b. Agitating a solution-stirring helps to bring fresh solvent into contact with the solute

c. Heating a solvent- increasing the temperature helps to separate the solute molecules

Solubility

• - the maximum amount of a substance that can be dissolved at a certain temperature

• What is a saturated solution?Unsaturated solution? Supersaturated solution?– It contains the maximum amount of dissolved solute

– It contains less solute than saturated solution

– It contains more dissolved solute than a saturated solution

Solubility Chart

What happens to Ionic Compounds in Water?

• They break up into their ions

• NaCl(aq) → Na+ + Cl-

• MgBr2 → Mg+ + 2Br-

Describing Reactions in Solutions

3 Types of Equations1. Molecular equation

K2CrO4(aq) + Ba(NO3)2(aq) BaCrO4(s) +

2KNO3(aq)2. Complete Ionic equation- represents the actual forms of

reactants and products

2K+(aq) + CrO4-(aq) + Ba+2(aq) + 2NO3

-(aq) BaCrO4(s) + 2K+

(aq) + 2NO3-(aq)

Spectator Ions- ions that do not participate directly in the reaction

K+ and NO3- are spectator ions

Con.

3. Net Ionic Equation- includes only those components that undergo changes in the reaction

Ba2+(aq) + CrO42-(aq) BaCrO4(s)

Concentration of Solutions

• What is Concentration?-a measure of the amount of solute in a given amount of solvent or solution

What is Molarity?- the number of moles of solute in one liter of solutionMolarity(M)= amount of solute(mol)

volume of solution(L)

M=mol/L

Molarity Example

• What is the molarity of a potassium chloride solution that has a volume of 400. ml and contains 85.0 g of KCl?

• Sodium thiosulfate, Na2S2O3, is used in developing photographic film. How many grams of Na2S2O3 are needed to make 100.0 mL of a 0.250 M solution?

Examples cont.

• How many mL of a 0.500 M solution of copper(II) sulfate, CuSO4, are needed to react with an excess of aluminum,Al, to provide 11.0 g of copper?

3 CuSO4 + 2Al 3Cu + Al2(SO4)3

Predicting Solubility

• How do we know if a solute will dissolve in a solvent?

• The general rule of thumb for predicting is the phrase “likes dissolve likes”

• Examples:• Ionic solutions will dissolve ionic solutions• Nonpolar will dissolve nonpolar• Polar will dissolve polar

Can insoluble substances mix?

• Yes, they can form an emulsion

• What is an emulsion?• Colloidal sized droplets of one liquid

suspended in another liquid• Oil and vinegar is an emulsion• Other examples are floor waxes,

shortening, milk, and butter

How do you make emulsions stay together?

• Emulsifying Agent- stabilizes an emulsion that would otherwise separate into different phases

• Lecithin is an emulsifying agent• Other examples are polysorbates, xanthan

gum, glycerides• A more common example is soap• Why do we use soap to wash our hands?

How are solubility principles used in real life?

• One use is in Dry Cleaning• Dry cleaning does involve liquids• The stain is treated with a compound like

tetrachloroethylene(C2Cl4) which loosens the stain and then is placed in a mechanical dry cleaner.

• It depends on the stain as to which compound is used.

Uses cont.

• A second use is carbonation. Carbonation gives soda it fizz.

• It depends on pressure.

• A third use deals with vitamins. Vitamins are classified as water or fat soluble. If it is fat soluble it can be stored in the body. If it is water soluble it can not be stored and you will need to replace that vitamin each day.