Chapter 18: Solution Chemistry

(Also including some Ch. 17!)

A few things you need to recall…

Ionic = metallic element + nonmetallic element Covalent = nonmetal + nonmetal

Polar Nonpolar

Examples:

Solutions:

Aqueous Solutions: Water that contains a dissolved substance. Kool Aid Salt water Magnesium chloride solution Vinegar

Solutions are made up of Solvents and Solutes:

Solute: The dissolving substance

Solvent: The medium in which a solute is dissolved.

Water is the mostcommon solvent

Dissolving NaCl

Dissolving Ionic Compounds

A molecular look at dissolving an ionic compound in water

http://www.chem.umass.edu/~botch/Chem112S05/Chapters/Ch14/SolvationIons.jpg

Solvation: process that occurs when a compound is dissolved in water.

Solute or Solvent?

Oil/Water Activity

In your beaker add about 20 mL of oil to 20 mL of water.

Do the two substances mix? Add 4-5 drops of food coloring to the

beaker? What happens? Based on your experiment, does food

coloring have properties that are similar to water or similar to oil?

Likes Dissolve Likes

Polar molecules dissolve in Polar solvents. Nonpolar solutes dissolve in nonpolar

solvents.

Ionic compounds and polar covalent compounds dissolve the best in water. Why?

Water is a polar compound

Mixing Oil and Water

Vinegar (acetic acid)

Olive Oil

Polar

Non-Polar

Oil and vinegar are immiscible – they do not dissolve in each

other.

Making Solutions

http://www.chem4kids.com/files/matter_solution.html

Factors that affect dissolving rate

How do you make sugar dissolve faster in iced tea?

1) Stirring = Agitation Changes rate, but not how much dissolves.

Factors that affect dissolving rate

Does sugar dissolve faster in hot tea or cold tea?

2)Temperature Kinetic Energy of water molecules increases;

more collisions with surface of sugar crystals

Factors that affect dissolving rate

Does granular sugar or a sugar cube dissolve fastest?

3) Particle Size More solute is exposed to water, dissolves faster

Homogeneous vs. Heterogeneous

Homogeneous = evenly mixed; same throughout

Heterogeneous = unevenly mixed; not the same throughout

Solubility: How much dissolves?

Solubility: The amount of solute that will dissolve in a solvent at a given temperature. Very temperature dependent. Usually expressed in

g/100mL (or g/100g H2O)

Examples:

Example #1: What is the solubility of sodium chloride at 70 °C?

Example 2:

Example #2: At 25 °C, how many grams of potassium nitrate will dissolve in 200 mL water?

Practical Applications

What are the optimum conditions to explode a can of coke on your little brother?

Why do divers have to worry about

how fast they return to the ocean

surface?

Warm Up 12/02/08

1. How many moles are in 510 g of AgNO3?

2. List the 3 factors that affect how fast a substance dissolves.

Types of Solutions:

Saturated Solution: Contains the max amount of solute at a given temperature. No more can be dissolved

Unsaturated: Contains less than max amount of solute

Types of Solutions

Supersaturated: Solutions that hold more solute than possible.

Real life supersaturation experience…

Rock Candy!

Factors Affecting Solubility

Temperature Solids: More soluble in hot solvent Gases: More soluble in cold solvent

Pressure Gases: More soluble at high pressure

Concentration of Solutions

Concentration is the amount of solute per amount of solvent.

To make Kool Aid:2 Scoops Kool Aid1 Quart Water

Describing Solutions

Version 1: No Math! (Qualitative)

Dilute :Low

concentration of solute

Concentrated :High

concentration of solute

½ scoop Kool Aid2 Quarts Water

2 ½ scoop Kool Aid2 Quarts Water

Common Chemistry Concentrations

Version 2 (MATH ) Molarity (M) Molality (m) Percent Composition

%m/%v %v/%v

Molarity

http://www.cartage.org.lb/en/kids/science/Chemistry/math/pix/molarity.gif

Example 1:

A solution has a volume of 2.0 L and contains 36.0 g of glucose (mm 180 g/mol). What is the molarity of the solution?

Example 2:

How many moles of ammonium nitrate are in 335 mL of 0.425 M NH4NO3?

Dilutions

Used when you want a less concentrated solution. Kool Aid Example:

Same number of moles of solute when you make a dilution:

M1 x V1 = M2 x V2

Initial MolarityOf Concentrated

SolutionInitial Volume Final Molarity

Of Dilute Sln

Final VolumeOf Dilute Sln

Example 3

Explain how to prepare 25 L of a 0.10 M BaCl2 solution, starting with solid BaCl2.

Specify the volume of the solution above to get 0.020 mol of BaCl2.

Example 3

How many mL of a stock solution (concentrated) of 4.00 molar potassium iodide would you need to prepare 250 mL of 0.760 M KI?

Percent Compostion

%(m/v) = (mass solute (g)) ÷ (mL solution) 100%

%(v/v) = (volume solute) ÷ (L solution) 100%

Example 4:

Determine the %(m/v) of a solution that is 20.0

g sugar in 401 mL solution.

Parts per million (ppm)

ppm = (mass solute (g)) ÷ (mL solution) 1,000,000