Solutions & Concentration. Water Polar molecule w/ polar bonds Causes surface tension & ability to dissolve polar molecules and ionic compounds.

Solutions & Concentration

WaterPolar molecule w/ polar bondsCauses surface tension & ability

to dissolve polar molecules and ionic compounds

Solutions

a.k.a. homogeneous mixtureSolutions can exist in any of the phases of

matter.Gases = Air (Nitrogen and Oxygen)Liquids = Vinegar (Water and Acetic Acid)Solids = Steel (Iron and Carbon)

What happens at the molecular level?

The solvent molecules surround the solute molecules, in a process called solvation.

Random motion of molecules causes mixing

Go to animation

Ionic compounds

Ions dissociate when they dissolve!This is what allows them to conduct

electricity when dissolvedCalled electrolytes

Heterogeneous MixturesSuspensions - mixture with large particles

that settle out if left undisturbedColloids - mixture with medium size

particles… larger than solution particles, but smaller than suspension particles

Amounts of Solute

Specific amounts of solute can be dissolved at each temperature and pressure.

Unsaturated = more solute can dissolveSaturated = maximum amount of solute

dissolvedSupersaturated = more than maximum amount

is dissolvedAchieved by increasing temperature, adding solute,

then slowly bringing temperature back down.

Sodium acetate demo!

^ supersaturated ^ unsaturated

sToP & tHinK: If you have 20 grams of KNO3 in 100 g of H2O at 50 C, is it unsaturated, saturated, or supersaturated?

1) How many grams of NaNO3 can dissolve in 100 g of water at 10 C?

2) At what temperature can 80 grams of KNO3 dissolve into100 grams of water?

3) How many grams of KNO3 can dissolve into 50 g of water at 40 C?

To Mix or Not To Mix…Not all substance combinations dissolve! Depends on

polarity/charge…

For a solid/gas solute in a liquid solvent:

If it dissolves… soluble

If it doesn’t… insoluble

For a liquid solute in a liquid solvent:

If it dissolves… miscible

If it doesn’t… immiscible

Oil / water

Factors that Affect Solubility

SOLID SOLUTE the temperature = solubility (usually, but

NOT always) the surface area = solubility

GAS SOLUTE temperature = solubility the pressure = solubility(like in the gas in soda pop lab!)

Alka-seltzer demo

QuickTime™ and aSorenson Video decompressorare needed to see this picture.

Solubility Video (5 min)

Calculating Concentration

1. Molarity (M)

2. percent composition (%)

3. parts per million (ppm)

4. grams/liter (g/L)

Molarity

M = moles of solute / liters of solutionExample: What is the molarity of 5 moles

of iodine dissolved in water, making 50 L of solution?

2 fish / 2 Liter 2 fish / 4 Liter

Molarity looks at the number of solute particles / volume of solution

Percent Composition

percent by mass = (mass of solute/mass of solution) x 100

percent by volume = (volume of solute/volume of solution) x 100

Example: You pack a suitcase that weighs 50 kg. You add 10 kg of t-shirts. What is the percent by mass of t-shirts?

Example: You add 5 mL of acetic acid to 95 mL of water. What is the percent by volume of acetic acid?

Parts per MillionParts per million is a measure of how many

parts of solute are in a million parts of solution.

ppm = (mass solute / total mass of solution) x 106

Imagine a jar that has a million jelly beans in it. (Yummie!) If 14 of the jelly beans were yellow we could say that the yellow jelly beans had a concentration of 14 parts per million.

Melamine audio ->

Grams per Liter

Grams per liter represents the mass of the solute divided by the volume of the solution.

g/L = grams of solute / liters of solutionExample: You have 20 grams of sodium

chloride dissolved in water with a total volume of 5 liters. What is the concentration of NaCl in grams/liter?

Molar Dilutions

Making solutions of lower concentrations from higher concentrations

M1V1 = M2V2

Example: What volume of a 3 M HCl solution is needed to make 2 L of 1 M HCl?

Example: How many liters of 6 M NaOH is required to make 2 L of 4 M NaOH?

Colligative Properties

physical properties affected by the NUMBER of solute particles, NOT the solute identityvapor pressure loweringboiling point elevationfreezing point depression

How would dissolving 1 mole of CaCl2 differ from 1 mole of NaCl in affecting colligative properties?

Club soda demo!

solutions have a wider range of P & T where they are in liquid phase