MIXTURES &

SOLUTIONS

Today you need:Today you need:

Materials to take notesMaterials to take notes

SC7. Students will characterize the properties that describe solutions and the nature of acids and bases.

• a. Explain the process of dissolving in terms

of solute/solvent interactions• b. Observe factors that effect the rate at which a solute dissolves in a specific solvent, • c. Express concentrations as molarities, • d. Prepare and properly label solutions of

specified molar concentration, • e. Relate molality to colligative properties.

The GPS StandardThe GPS Standard

SOLUBILITY

SolubilitySolubility

maximum grams of solute that will dissolve maximum grams of solute that will dissolve

in 100 g of solvent at a given temperaturein 100 g of solvent at a given temperature

varies with temperaturevaries with temperature

based on a saturated solutionbased on a saturated solution

SOLUBILITYSOLUBILITY

SATURATED SOLUTION

no more solute dissolves

UNSATURATED SOLUTIONmore solute

dissolves

SUPERSATURATED SOLUTION

becomes unstable, crystals form

increasing concentration

SOLUBILITY CURVES

• Solubility of solidssolids increase with increases in temperature.

• Solubility of gasesgases in liquids decrease with increasing temperature

• WHY?

THE EFFECT OF TEMPERATURE ON SOLUBILITY IS DEPENDENT ON THE

PHASE OF MATTER.

To

S

To

S

Solids or liquids dissolved in liquids Gases dissolved in liquids

As To , solubility As To , solubility

WHAT IS THE SOLUBILITY OF____ AT ____°C?

SOLUTION CONCENTRATION

THINK ABOUT IT…

• you probably are familiar with the difference between what is called a "weak" solution or a "strong" solution. 

CONCENTRATION…

The measure of how much solute is dissolved in The measure of how much solute is dissolved in a specific amount of solvent or solution.a specific amount of solvent or solution.

a measure of solute-to-solvent ratio

concentrated vs. dilute “lots of solute” “not much solute”

“watery”

Add water (hydrate) to dilute

remove water (evaporate by boiling) to concentrate

CONCENTRATIONS

• Qualitative (words): -Concentrated-dilute

• Quantitative (numbers):-percent by mass-percent by volume-Molarity (M)-molality (m)

WHAT IS THE [SOLID SOLUTE] IN A LIQUID SOLVENT?

WHAT PART?

OUT OF WHAT WHOLE?

Read the above as: What is the concentration of solid solute in a liquid solvent?

Percent by mass = mass of solute x 100 mass of solution

PERCENT BY MASS

Mass of solution = mass of solute + mass of solvent

Use when combining a solid solute into a liquid solvent

Mass of Solvent?

FINDING MASS OF SOLVENT

Or finding the mass of a volume.

Is there a relationship b/w mass and volume?-- Density or D ---- Density or D --

D = m/V or m = DV

Since our solvent is H2O and we know that the

DH2O = 1.0 g/ml (constant)

So, m = DV or

m = (1.0 g/ml) (V)

EXAMPLE PERCENT BY MASS:To maintain a sodium chloride (NaCl) concentration

similar to ocean water, an aquarium must contain 3.6 g NaCl per 100.0 g of water. What is the

percent by mass of NaCl in the solution?

Given:Given:Mass of solute: 3.6 g NaClMass of solute: 3.6 g NaClMass of solvent: 100.0 g HMass of solvent: 100.0 g H22OO

Equation:Equation:

Percent by mass = mass of solute x 100 Percent by mass = mass of solute x 100 mass of solution mass of solution

= 3.6 g NaCl x 100 3.6 g NaCl + 100.0 g H2O

= 3.5 %

What is the percent by mass of NaHCO3 in a solution containing 20.0 g of NaHCO3 dissolved in

600.0 mL of H2O?

BUT WHAT IF THE SOLUTE AND SOLVENT ARE BOTH LIQUIDS?

What does this mean?

What does this mean?

PERCENT BY VOLUME

volume of solutePercent by volume = x

100 volume of solution

TRY CALCULATING PERCENT BY VOLUME:

What is the percent by volume of ethanol in a solution that contains 35 mL of ethanol dissolved

in 155 mL of water?

Percent by volume = Percent by volume = volume of solute volume of solute x 100x 100

volume of solutionvolume of solution

How much isopropyl alcohol is actually in a 473 mL solution of 99 % isopropyl alcohol?

Percent by volume = Percent by volume = volume of solute volume of solute x 100x 100

volume of solutionvolume of solution

MOLARITY

Molarity (M) = moles of solute Liters of solution

The unit M is read, “molar”

What is the molarity of an aqueous solution containing 0.22 mol of glucose (C6H12O6) in 1.5 L of

solution?

CALCULATING MOLARITY:

A 100.5 mL solution contains 5.10 g of glucose (C6H12O6). What is the molarity of this solution? (The molar mass of glucose is 180.16 g/mol.)

Remember, Molarity is just a measure of how concentrated a solution is

(or how “strong” it is)… so,

Which is the most concentrated solution?

a) 0.50 M CuSO4

b) 1.75 M CuSO4

c) 3.00 M CuSO4

d) 7.00 M CuSOd) 7.00 M CuSO44

Which is the least concentrated solution?

a) 0.25 M HCla) 0.25 M HClb) 0.75 M HClc) 2.00 M HCld) 4.25 M HCl

We know from Guy Lussac’s Law that V of a solution changes with T.

This change in V alters the M of the solution.

We also know that mass does not change with T.

So, sometimes it is more useful to describe solutions in terms of how many moles of solute are dissolved in a specific mass of solvent.

MOLALITY

Molality (m) = moles of solute kg of solvent

You LOVE me!!The unit m is read, “molal”

CALCULATING MOLALITY:In the lab, a student adds 4.5 g of sodium chloride

(NaCl) to 0.1 kg of water. Calculate the molality.

What is the molality of a solution containing 10.0 g of Na2SO4 dissolved in 2000.0 g of water?

In the lab, you might use concentrated solutions of standard molarities, called stock solutions.

But, you can prepare a less-concentrated solution by diluting the stock solution with additional

solvent.

MAKING A DILUTE

SOLUTION

initial solution

removesample

diluted solution

same number ofmoles of solutein a larger volume

mix

moles ofsolute

2211 VMVM

DILUTION

• Preparation of a desired solution by adding water to a concentrate.

• Moles of solute remain the same.

M = Molarity (Concentration), V = volume

Dilution Equation:

M1V1 = M2V2

M1 and V1 represent the molarity and volume of the stock solution, while M2 and V2 represent the molarity and volume of the dilute solution.

So for instance, what volume, in mL, of a 2.00M calcium chloride (CaCl2) stock solution would you use to make 0.50 mL of 0.300M calcium chloride

solution?

What volume of a 3.00M KI stock solution would you use to make 0.300 L of a 1.25M KI solution?

CONCENTRATION“THE AMOUNT OF SOLUTE IN A SOLUTION”

A. % mass = mass of solute mass of sol’n

B. % volume = V of solute V of sol’n

C. molarity (M) = moles of solute L of sol’n

– used most often in this class

D. molality (m) = moles of solutekg of solvent

M = mol L

% by mass – medicated creams

% by volume – rubbing alcohol

E. M1V1 = M2V2 dilutions