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
- Gaseous solutions - air
- Liquid solutions – vinegar (acetic acid dissolved in water); soft drinks (solutions of a gas, CO2, dissolved in water.
- 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)
Classify as either a solution or colloidRubbing alcohol / Milk
Medicine / Vinegar
H2O2 / Windex
Gasoline / Mayonnaise
Hairspray / Jello
Scope / 7-up (don’t worry about the same phase)
Toothpaste
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...
Dissociation - separation of ;caused by the action of the . / Hydration- the process of particles being surrounded by .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:
Concentration (molality) / Actual change in the freezing point / Theoretical change in the freezing point / % dissociation.1 / - 0.346 / - 0.372 / 93 %
.01 / - 0.0361 / - 0.0372 / 97 %
.001 / - 0.00366 / - 0.00372 / 98 %
.0001 / - 0.000372 / - 0.000372 / 100 %
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”
12_Notes_T Page 1 of 20