Inquiry Activity Things that determine how fast a substance will dissolve 1. Stirring (agitation) 2....

SOLUTIONS!

Inquiry ActivityThings that determine how fast a substance

will dissolve1. Stirring (agitation)2. temperature3. surface area of the dissolving particles

What is a solution?A homogeneous

mixture of two or more substances.

What is the difference between a solute and a solvent?

Solvent: the dissolving mediumUsually water

Solute: dissolved particlesAtoms, ions, or molecules

that are less than 1nm in diameter.

Solutes and solvents can be solid, liquid, or gas

How does it work?As individual solute

particles (ions) break away from crystal (NaCl), the – and + ions become surround by solvent molecules (water) and crystal dissolves.

What about oil and water?Nonpolar covalent bonds

do not dissolve in water (a polar covalent bond)

However, oil and gasoline DO mix. Both are nonpolar molecules, so the molecules can easily break up and re bond.

“LIKE dissolves LIKE”

What is solubility?The amount of

substance that dissolves in a given quantity of solvent at a specific temperature and pressure

(grams of solute/liter)

Example: If you add 36g NaCl to 100g water at 25 degrees Celcius, all 36g dissolves, but if you add 1 more gram, only .2 of it will dissolve.

WHY? The solution is

SATURATED!

What is the difference between saturated and unsaturated solutions?Saturated: contains

the amount of solute for a given solvent at constant temperature and pressure

Unsaturated: A solution that contains less solute than a saturate solution at a given temperature and pressure.

What Factors Affect Solubility?1. Temperature

Solid and liquid solutions Solubility as temp

Gaseous solutions Solubility as temp

2. Pressure (gas solutes only) Solubility of gases as

pressure

How can concentration of a solution be expressed quantitatively?

Molarity (M): # of moles of solute dissolved in 1 L of solution.

Molarity (M) = moles of solute Liters of solution

Practice!

IV solutions at hospitals are often administered to patients. One saline solution contains .9g NaCl in exactly 100 ml solution. What’s the molarity?

First! Convert grams to moles, then ml to L

Practice!A solution has a volume of 2.0L and

contains 36 g of glucose (C6H12O6). If the molar mass of glucose is 180g/mol, what is the molarity of the solution?

Making DilutionsDiluting a solution reduces the number of moles of

solute per unit volume, but the total # of moles in the solution doesn’t change.

Moles of solute: M1 x V1 = M2 x V2

How many milliliters of aqueous 2M MgSO4 solution must be diluted with water to prepare 100ml of

aqueous .4M MgSO4?

Practice!How many

milliliters of a solution of 4M KI are needed to prepared 250 ml of .760M KI?

Think of concentrated juice!

How is solubility affected by pressure?Practice

If the solubility of a gas in water is .77g/L at 3.5 kPa of pressure, what is its solubility (in g/L) at 1.0kPa of pressure (The temperature is held constant at 25 degrees C)

Henry’s Law: at a given temperature, the solubility (S) of a gas in a liquid is directly proportional to the pressure (P) of the gas above the liquid.

S1 = S2P1 P2

Let’s try another!

The solubility of a gas in water is .16g/L at 104kPa. What is the solubiluty when the pressure of the gas is increased to 288 kPa?

A gas has a solubility in water at 0 degrees Celcius of 3.6 g/L at a pressure of 1.0 atm. What pressure is needed to produce an aqueous solution containing 9.5g/L of the same gas at 0 degrees Celcius?