Accelerated Chemistrychapter 12 Note Packet

Accelerated Chemistry

Chapter 12–Solutions

Accelerated ChemistryChapter 12 Note Packet

Bookwork: page 426 #7,9,11,12,20,22,28,29,30

Page 459# 19,21,25

12.1 Types of Mixtures

What is a Mixture?

A combination of kinds of matter, each retains its own

.

Homogeneous: a mixture composition (ex: water).

Heterogeneous: a mixture composition (ex: water).

Solutions

A homogeneous mixture in a single .

Properties:

1) distribution of particles

2) settle out

3)

4) filtered out (small particle size)

The nature of solutions:

Solute: the part that .

Solvent: the part that .

Aqueous: (aq) a solution that contains as the solvent.

Tinctures: solutions that contains as the solvent

Examples: I2 in alcohol

phenolphthalein solutions

Solutions can be electrolytes or non-electrolytes.

What is an electrolyte?

Salts. Anything that dissolves in water and conducts .

Solutes are classified according to whether they dissolve to form neutral molecules or charged .

Solutes dissolve to form

MoleculesIons

(non-electrolytes)(electrolytes)

3 Types of solutions

1. Gaseous solutions - air

1. Liquid solutions – vinegar (acetic acid dissolved in water); soft drinks (solutions of a gas, CO2, dissolved in water.
2. Solid solutions – alloys such as sterling silver – 92% silver, 8% copper; white gold – gold containing nickel, tin, zinc or copper.

Suspensions

A heterogeneous mixture of .

Example – a jar of muddy water

Colloids

Colloids contain intermediate size particles that remain in suspension because they are too .

Example – the large particles settle out of the muddy water, but the water remains cloudy. The cloudy water cannot be filtered because the particles are too small and remain in suspension due to the constant movement of the liquid molecules.

Colloids include – mayonnaise (solid emulsion), foam, smoke (solid dispersed in gas), fog (liquid dispersed in gas)

Classification of Matter Chart

12.2 The solution process

Factors affecting the rate of dissolving

Degree of Solubility: the amount of substance required to form a solution in a certain amount of at a certain .

solute+solvent ↔

(equilibrium)

If you wish to dissolve a substance, you can help by (FIGURE 14.6):

1. (increase surface area)2. 3.

Factors affecting solubility:

1. Types of solvents and solutes –“Like dissolves like”

Polar/ionicversusnonpolar

wateroil

saltgasoline

sugarStyrofoam

Ionic substances dissolve in polar substances – salt dissolves in

Non polar substances dissolve in non polar substances – fats, oils, gasoline dissolve

Immiscible substances in each other (salad dressing – oil and vinegar)

Miscible substances in each other (gasoline and benzene)

2. Pressure (gases only)

As pressure increase, solubility

Henry’slaw: solubility is to pressure.

Effervescence: the escape of a from a solution (a carbonated soft drink effervesces when the bottle is opened and the pressure is reduced)

Graph for gases:

S

P

3. Temperature

For most solids, solubility increases as temperature

Graph for solids:

S

T

For gases, solubility decreases as temperature .

Graph for gases:

S

T

Heats of solution

Solubility, the nature of solute and solvent, and the energy changes during solution formation

Dissolving an ionic compound in water:

Na+ Cl- Na+ Na+

Cl- Na+O-2O-2

Na+ Na+

+H+H+ H+H+O-2

Cl- Na+ O-2Cl-Cl-

Na+ Cl-H+H+

H+H+ Cl-Cl-

Step #1Step #2Step #3

Breakup theBreakup theFormation of the

( )( )( )

If step #1 plus step #2 are more than step #3, then the overall reaction is .

Energy Level Diagram:

(most solutions are

)

If step #1 plus step #2 are less than step #3, then the overall reaction is .

Energy Level Diagram:

Heat of Solution: The amount of heat when a solute dissolves in a solvent.

Heat of Hydration: energy when are surrounded by molecules.

The # of water molecules used depends on the .

↑ Heat released (more ) as the of the ion

Li+1-523 kJ/mole versusNa+1 -418 kJ/mole

↑ Heat released (more ) as the of the ion

Na+1-418 kJ/moleversusMg+2-1949 kJ/mole

Li and Mg are close to the same size, so...

Remember: polar/ionic dissolves

O2 and CO2 are . They don’t dissolve very much in (just enough for sodas and fishies).

Solubility curves and tables

Solubility Rules:

soluble (definition): more than 1 g of solute dissolves per 100 g of water

slightlysoluble: between 0.1 and 1 g dissolves

insoluble: less than 0.1 g dissolves

d = decomposesni - not isolated - not been found to form

Saturated, unsaturated, and supersaturated solutions

Saturated Solution:

Holds as much as it can at a given and certain amount of

must be stated when determining solubility.

For gases, must also be stated when determining solubility.

Unsaturated Solution

The solution is currently dissolving less than the maximum amount of at a given .

Supersaturated Solution

The solution currently holds than the maximum amount of at a given .

How is this possible? These solutions are created by saturating a hot solution and allowing it to .

Ex1: What is the solubility of potassium chlorate at 50.0 oC in 100.0 ml of water?

Ex2: What temperature will result in a saturated solution of 80.0 grams of sodium nitrate and 100.0 grams of water?

Ex3: If 40.0 grams of ammonium chloride are placed in 100.0 grams of water at 50.0 oC, is the solution saturated or unsaturated? If saturated, how much salt remains undissolved? If unsaturated, how much more salt can be dissolved?

Ex4: If 80.0 grams of potassium nitrate are placed in 100.0 grams of water at 44.0°C, is the solution saturated or unsaturated? If saturated, how much salt remains undissolved? If unsaturated, how much more salt can be dissolved?

Ex5: What is the solubility of lithium sulfate at 90.0 oC in 50.0 ml of water?

Ex6: What is the solubility of lithium sulfate at 90.0 oC in 200.0 ml of water?

Ex7: What is the solubility of lithium sulfate at 90.0 oC in 68.2 ml of water?

12.3 Concentrations of solutions

Dilute vs. Concentrated

Dilute: a amount of solute in a amount of solvent.

Concentrated: a amount of solute in a amount of solvent.

Do not confuse with saturated and unsaturated. For example, “a saturated solution may be either dilute or concentrated.”

Not very useful terms in science, solutions have to be able to be duplicated exactly to be useful.

Ex: strong vs. weak coffee – both are relative to the taster.

% by Mass of a Solute in Solution

Example: Suppose we have a solution that contains 50.0 ml of alcohol (solute) and 50.0 ml of water (solvent). If the density of the alcohol is 0.800 g/mL, calculate the following percent solutions.

General Formula  (solute/solution) * 100 = % by mass

Weight of solute x 100 or Weight of solute x 100

Weight of solution Weight of solute + Weight of solvent

Ex1: Calculate the percent of 2.75 grams of NaCl in 40.0 grams of solution.

Ex2: Calculate the percent of 2.75 grams of NaCl in 40.0 grams of water.

Ex3: How many grams of C6H12O6 are needed to prepare 250.0 grams of

a 5.25% solution?

Molarity

A method used to calculate concentration.

Molarity (M) = moles solute

Liters of solution

Note: If given grams, use the p-table to find the number of moles

When you talk about a solution with a label of 6 M HCl, we say, “ Six solution.”

Ex1: Calculate the Molarity of a solution containing 5.25 grams of NaCl in

Ex2: How many grams of NaOH are needed to prepare 2.5 L of .50 M solution?.

Molality

Another method used to calculate concentration.

molality (m) = moles solute

kg of solvent

Ex1: Calculate the molality of a solution made by adding 7.25 grams of AlCl3 to

500.0 grams of H2O.

Ex2: Calculate the molality of a 15.0 % KBr solution.

Ex3: How many grams of C6H12O6 are needed to add to 500.0 grams of water to

make a .750 molal solution?.

When you talk about a solution with a label of 6 m HCl, we say, “ Six solution.”

The dilution formula:CoVo= CnVn

Ex1: What is the molarity of a solution made by adding 35.0 ml of a 6.00 M HCl solution to 100.0 ml of water?

+=

Use the dilution formula to calculate the molarity of the diluted HCl: CoVo= CnVn

Ex2: How many ml of a solution containing 11.70 grams of NaCl in 200.0 ml of solution would be needed to prepare 500.0 ml of a 0.0500 M solution?



First, calculate the molarity of the original solution: convert 11.70 g NaCl to moles

Now, use the dilution formula to calculate the ml of NaCl solution needed:

CoVo= CnVn

Colligative Properties of Solutions

Solutions that conduct electricity contain electrolytes.

Ionic compounds :

NaCl(s) + H2O(l) yields

MgCl2(s) + H2O(l) yields

)

Acids (dissociation of a covalent compound):

HCl(g) + H2O(l) yields

H2SO4(l) + H2O(l) yields

Substances that are not acids, bases, and salts do not dissociate/ionize.

When solutes dissolve in liquids, they the freezing point.

Two factors affect the degree of change in the temperature: the amount of the andthe nature of the .

Colligative properties: a property that depends on the

. Freezing point and boiling point are colligative properties.

∆tf = kf (m) book formula - not true

∆tf = kf (m)(x)truex = # of produced when the solute dissolves

kf water = -1.86 oC/m

Why does freezing point depression occur?

ONa+O

HH …………O …………HH

HH

Cl-

The solute (NaCl) interferes with . (ex: antifreeze)

As the number of solute particles increase, the freezing point .

Ex1: Calculate the freezing point of 10.00 grams of NaCl in 200.0 grams of water.

Boiling point elevation

Same concept as freezing point depression except boiling point .

kb water = 0.512 oC/m

Why does boiling point elevation occur?

The solute takes up space on the of a liquid. This decreases the ability of the liquid to . Thus, the vapor pressure decreases. Boiling occurs when the atmospheric pressure the vapor pressure. So, an in energy is needed to increase the vapor pressure to reach the atmospheric pressure.

= solvent

versus

= solute

“A”“B”

Which would produce more vapor?

Which would have a higher vapor pressure?

Which would take less energy to raise the vapor pressure to atmospheric pressure?

Which would have a higher boiling point?

Ex1: Calculate the boiling point of a solution of 10.00 grams of NaCl in 200.0 grams of water.

NIB Ion Pairing

When experiments are done regarding freezing point depression and boiling pointelevation, the actual answers are different than the answers (surprise, surprise!).

Example: a solution of NaCl in water:

Sodium Chloride can dissociate at a rate of 100% if the concentration of the solution is very . With increased concentration, ions may come in contact with each other and resulting in than 100% dissociation. Only at low, low concentrations do solutions have their approach the theoretical value.

Draw picture of ion pairing here

Theoretical:Actual:

X = ionsX = “ions”

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