FACTORS AFFECTING SOLVATION14.3: Pgs. 489 - 497

STEP 1 OF LAB1. Obtain a CLEAN test tube!!!2. Place 2.2 grams of Na2SO4 into a test tube

and add 10mL of water.3. Dissolve the solid: Heat the test tube in a

bunsen burner until you hear a “pop”. Remove the test tube from the bunsen burner and stir the contents with a stirring rod. Continue this process until the solid dissolves.

4. Place the test tube into the test tube rack when the solid is dissolved.

5. Place 2 ice cubes into a beaker and fill the beaker with water (You will use this later)

6. Sit back in your seat.

SOLUTION FORMATION What did you do to make the solid dissolve faster?

SOLUTION FORMATION Factors Affecting Solubility Rate:

1. Agitation stirring increases the rate at which a solute dissolves

Only affects the rate, NOT the amount!

2. Temperature hot solvents dissolved solutes faster than cold solvents

3. Particle Size fine powders dissolve more rapidly than large particles

Think about sugar cubes vs. table sugar!

4. Pressure refers to gases only!

SOLUBILITY

Saturated Solutions: contain the maximum amount of solute for a given amount of solvent Solubility is the amount of solute that dissolves

in a given quantity of a solvent at a given temperature to produce a saturated solution (i.e. NaCl = 36.2g per 100 mL H2O)

Unsaturated solutions contain less than the maximum

SOLUBILITY

STEP 2 OF THE LAB 1 person from your team must place your

test tube into the beaker of ice water and then return to your seat.

DYNAMIC EQUILIBRIUM

In saturated solutions, the rate of new particles dissolving vs. dissolved particles recrystalizing is EQUAL!

SOLUBILITY

Supersaturated solutions Contains more solute than is allowed at a given

temperature.

SOLUBILITY OF GASES

Gases have greater solubility in cold water then hot water why?

Gas solubility increases as the partial pressure above the solution increases – why?

SOLUBILITY OF GASES Sodas are bottled at

HIGH pressures! When the bottle is

opened, the CO2 escapes because the partial pressure of CO2 above the liquid decreases

SOLUBILITY OF GASES

Henry’s Law At a given temperature, the solubility of a gas (S) is

directly proportional to the pressure (P) of the gas above the liquid

2

2

1

1

P

s

P

s

PRACTICE PROBLEM:

If the solubility of a gas in water is 0.77g per 100mL of water at 3.5atm of pressure, what is its solubility (in g per 100mL of water) at 1.0atm of pressure. (Assume the temperature remains constant.)

LAST STEP OF THE LAB

GENTLY remove the test tube from the cold water. Add a small amount of Na2SO4 and observe.

Clean up the lab: All solution/compounds can be rinsed down the drain.

Sit back in your seat.

WHAT HAPPENED? How should we label the solution before we

added the crystal? Supersaturated solution Contains more solute than is allowed at a given

temperature. Supersaturated solutions are unstable.

If a small crystal of the solute is added to a supersaturated solution, the excess immediately crystallizes out.

How should we label the solution after the crystal was added? unsaturated

YESTERDAY WE COVERED…

4 factors that will increase the rate of dissolution

Today we will cover… How temperature not only increases

the rate of dissolution, temperature also affects the amount that can dissolve.

FACTORS AFFECTING SOLUBILITY

Solubility is VERY temperature dependent! Ex: 36.2g of NaCl dissolves in 100g H2O at 25oC,

HOWEVER 39.2g NaCl can dissolve in 100g H2O at 100oC!

For most substances, solubility increases as temperature of the solvent increases

SOLUBILITY CURVES What substance has

the highest solubility at 50oC? (exclude KI)

What has the lowest at 50oC?

PROBLEM:

I dissolved 5.2g of a substance into 16g of water. What is the solubility of this substance in units of g / 100g of water?

SOLUBILITY CURVE LAB

Not all substances are stable enough to create a supersaturated solution. Most substances can only form a saturated solution.

We will complete this as a class. Each pair of students will be assigned a specific amount of salt to use and we will collaborate our data to create a lab report.