All solutions have at least two parts:

• Solute:

• Solvent:Part of solution present in largest amount

Substance that is dissolved, present in a smaller amount

What happens when you cool a solution or let it sit for a long time?Precipitates: A solid that comes back out of its

solution due to a chemical reaction.

Temp.

2 KI(aq) + Pb(NO3)2(aq) PbI2(s) + 2 KNO3(aq)

Why do solutes seem to disappear in a solvent? Whenever a solution forms, particles of the solute leave each other and become surrounded by particles of the solvent.

Why does the solute dissolve in a solvent? When a solute is dropped into a solvent, the

solvent molecules “attack” the solute and pull it apart.

Solvent-solvent interactions

This happens only if the solvent-solute attraction is higher than the solvent-solvent interactions and solute-solute interactions.

Polarity of Water

Dilute:

Concentrated:

• describes how much solute is present in a solution compared to the amount of the solvent

• These two terms are used when comparing the [ ] of two solutions with the same type of solute and solvent

A mixture that has little solute dissolved in it

A mixture that has a lot of solute dissolved in it

Concentration

• measurement that describes the limit of how much solute dissolves in a given amount (100 g) of solvent at a given temperature.

Yet another CHARACTERISTIC PHYSICAL PROPERTY!

- in other words, a measure of how well a solute dissolves in a solvent at a given temperature.

Unsaturated solution:

Saturated solution:

A mixture in which more solute can dissolve

A mixture that has the maximum amount of solute that can dissolve

HUH???HUH???

Solubility

Solubility in 100 g water at 0º C

Compound Solubility

Salt (NaCl) 35.7

Baking Soda (NaHCO3)

6.9

Carbon Dioxide (CO2)

0.348

Sugar (C12H22O11) 180

Each compound listed in the table dissolves in water, but they have different solubilities.

Which compound is the most soluble?

Which compound is the least soluble?

Quiz

1. What two parts make up a solution?

2. If you are not part of the solution, you are part of the ___________________

3. Two ways to describe the concentration of a solution are _______ and ___________________.

4. A ______________________ solution cannot hold any more solute at a given temperature.

5. _____________ describes how well a solute dissolves in a solvent at a given temperature.

6. ___________________describes how much solute is present in a solvent

Quiz-Answers

1. What two parts make up a solution? Solute and solvent

2. If you are not part of the solution, you are part of the ____precipitate____

3. Two ways to describe the concentration of a solution are __dilute___ and ____concentrated________.

4. A _____saturated_______________ solution cannot hold any more solute at a given temperature.

5. __Solubility___________ describes how well a solute dissolves in a solvent at a given temperature.

6. Concentration_________describes how much solute is present in a solvent

Why doesn’t a solute added to a saturated solution dissolve?

Factors that Affect Solubility• Temperature• Nature of solute and solvent• Pressure (gases only) (Not discussed here)

In most cases, solubility increase with an increase in temperature (liquid-solid solutions). There are some exceptions to this.

Gases are more soluble in colder solvents than in hotter solvents (liquid-gas solutions)

Effect of temperature

WHY? Entropy!Gases have highest entropyLiquids are in the middle.Solids have the lowest entropy

Factors that Affect SolubilityNature of the solute and solvent

Size of molecule of the soluteAttraction to solute/solvent particles

Factors that Affect Rate of Solution

Rate of Solution: a measure of how fast a substance dissolves

• size of particles• stirring• amount of solute already dissolved• temperature

Factors that Affect Rate of SolutionSize of Particle

Breaking up the solute into smaller pieces increases the surface area – area of contact between solute and solvent

Factors that Affect Rate of Solution

Stirring

• Brings fresh portions of the solvent in contact with the solute, thereby increasing rate of dissolving

Amount of Solute Already Dissolved

Factors that Affect Rate of Solution

When there is little or no solute in solution, dissolving takes place relatively rapidly.

As the solution approaches saturation, dissolving takes place more slowly.

Factors that Affect Rate of Solution

For liquids and solid solutes, increasing the temperature not only increases the amount of solute that will dissolve but also increases the rate at which the solute will dissolve.

For gases, the reverse is true. An increase in temperature decreases both solubility and rate of solution.

Temperature

Solubility Curves- Used to determine the SOLUBILITY of a compound at a particular TEMPERATURE.

- ON the curve indicates that the solution is SATURATED. -BELOW the curve indicates that the solution is UNSATURED.

- ABOVE the curve indicates that the solution is SUPERSATURATED.

Solubility QuestionsWhat substance has a solubility of 90 g/100mL of water at a temperature of 25ºC ? At 45 degrees celcius, what is the solubility of sodium nitrate?   At what temperature will sodium nitrate have a solubility of 95 g/100cm3

  What is the solubility of sodium chloride at 45 degrees celcius? What is the solubility of sodium chloride at 25ºC in 150 cm3 of water ?   30 grams of potassium nitrate has been added to 100 mL of water at a temperature of 50ºC. How many additional grams of solute must be added in order to make it saturated?