Unit 7: Solutions, Acids, & Bases. I. Definitions and Types of Solutions A. What exactly IS a...

Unit 7:

Solutions,

Acids, & Bases

I. Definitions and Types of Solutions

A.What exactly IS a Solution?

B. Types:

[Vocabulary terms…]1] Unsaturated

2] Saturated

3] Supersaturated

4] Suspensions

5] Colloids

6] Alloys

Question…

HOW do we create solutions?

C. Forming Solutions

Polar solvents mix best with __________solutes!

How do IMF’s relate to this concept?

Nonpolar solvents mix best with ________________ solutes!

Examples…

Like Dissolves Like…

See Table 7.1 on pg. 119 of Review book!

SoluteNonpolar Solvent

Polar Solvent

Nonpolar

Polar

Ionic

II. Collision Theory

Molecules need the proper orientation and proper amount of kinetic energy to create a solutionRemember the formation of Salt Water

demonstrations? How did the orientation of the water impact

the solvation of the Na+ and Cl- ions?

Combining the Solute and Solvent

Two major criteria need to be met:1: “Like Dissolves Like” = need

compatible bond types and IMF’s

2: Effective Collisions = For a substance to dissolve into a solvent, there must be an “effective collision” between solute and solvent

Need sufficient KE and proper orientation!

Factors Affecting the Formation of a Solution

1] TemperatureTemperatureIncrease in Temp = Increase in KE, & increase in # of total collisions

3] PolarityPolaritySimilar bond types and IMF’s form solutions faster

2] Surface AreaSurface AreaIncrease in S.A. means more particles contact the solution, & increases the total # of collisions

4] Pressure (gases only)Pressure (gases only)Increases in Pressure cause decreases in volume, and make gases more soluble

Other Solutions Terms…

Precipitate out = this refers to the solid precipitate that ‘falls out’ of a solution when an irreversible double replacement reaction occurs; Solid may be collected!

Miscible = substances that completely and evenly mix together at any concentrations

Immiscible = do NOT mix to form a solution

Forming Solutions

Temperature Changes: Increases = most

solids have higher solubilities

EXCEPTION = gases!

Lower solubility at higher temperatures

Pressure Changes: Increases = most

gases have higher solubilities

Liquids and solids = Exceptions!

Little to no solubility differences with changes in pressure

III. Collision Theory

Collision theory = scientific description of how solutions are formed

May have several factors that help collisions occur faster

Need _____________ collisions with particles that have sufficient __________ for a solution to occur!

Do you have any ideas on how to speed up this process…?

II. Solubility Curves and Guidelines

A. Table G: Solubility Guidelines for Aqueous Solutions

Supersaturated = ABOVEABOVE

Saturated = ONON the line

Unsaturated = BELOWBELOW

B. Table F: Solubility Guidelines for Aqueous Solutions

These charts tell if an anion or cation is generally soluble in water

Exceptions occur for half of those listed

General rules of solubility here; not a total and complete list!

Determine solubility…

C. Net Ionic Equations

http://www.youtube.com/watch?v=RjBjwQF276ANet ionic equations are generated when ions

react within a solution to form a precipitate [solid]The ions involved in creating the solid will be

eliminated from the solution, eventuallyThe ions that are eliminated produce the “net”

reaction, or equation! [example on board]

http://www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/crm3s2_3.swf

IV. Measuring Concentrations

A. Percent Mass (w/w)

B. Percent Volume (v/v)

C. Parts per Million (ppm)

D. Parts per Billion (ppb)

Let’s practice…

What is the concentration of a solution, in parts per million, if 0.02 gram of NaCl is dissolved in 1000. grams of solution?

Regents Practice Problems

An aqueous solution has 0.0070 gram of oxygen dissolved in 1000. grams of water.

------------------------------------------------------------

Calculate the dissolved oxygen concentration of this solution in parts per million.

[Your response must include both a correct numerical setup and the calculated result.]

D. Molarity

moles solute

Molarity (M) = Liter solution

Solute MUST be in units of ‘moles’

Solvent MUST be in units of ‘Liters’

May use Molarity to find grams, moles, or molar mass

Molarity Examples

1] Calculate the molarity of a solution containing 35.0g NaCl dissolved into 500mL of water.

2] How many grams of NaCl are needed to make 650mL of a 0.010M solution?

E. Dilutions

Dilutions use Molarity and Volume to distribute the moles of a substance

McVc = MdVd

(Molarity) x (volume) in Liters = moles!Extremely useful equation!!!

Dilution Examples

1] Calculate the new molarity of 1500.mL of solution made from 25.mL of 12M.

2] How much 18M acid is needed to make 2500mL of 0.10M solution?

V. Colligative Properties

Colligative properties…

properties of solutions that depend on the number of molecules in a given volume of solvent and not on the properties/identity (e.g. size or mass) of the molecules

Colligative properties

These include: lowering of vapor pressureelevation of boiling pointdepression of freezing point

They are based on the number of particles or electrolytes produced in a solution by a solute

A. Electrolytes vs. Particles

Electrolytes are….

They conduct electricity!

Number of electrolytes formed per molecule depends on the # of ions it breaks into!

Ex.]

Particles are…

They DO NOT conduct electricity!

Produce only ONE particle per molecule dissolved!

Ex.]

B. Factors Affected

1] Freezing Point DepressionFreezing Point Depression

Adding particles/electrolytes causes the freezing point of the solution to be less than that of the pure substance

Magnitude of change depends on # of particles/ions in solution

2] Boiling Point ElevationBoiling Point Elevation

Adding particles/electrolytes will cause the boiling point to increase for the solution

Can calculate the new boiling point using an equation

Web demos

http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/propOfSoln/colligative.html

2. Vaporization and Boiling

Vapor pressure = the pressure exerted by a layer of the gas phase on the surface of a liquid or solidHigh Vapor pressure = weaker IMF’s,

weaker bonds, changes to gas phase easilyLow vapor pressure = STRONGER IMF’s,

stronger bonds, and prefers to remain a liquid phase

Table H Vapor Pressure of Four

Liquids

3. Boiling Point vs. Normal Boiling Point

Boiling Point = temperature at which vapor pressure of the liquid equals the atmospheric pressure of the surroundings

NORMAL boiling point = temperature when the vapor pressure

equals standard pressure [1atm]

What changes the boiling point?

Changes in atmospheric pressure cause changes in the boiling point

Low pressure at higher altitudes cause the boiling point to be lower than normal [pressure is lower than normal…]

High pressure occurring below sea level cause boiling points to increase […?]

Vapor Pressure… REVIEW…

Vapor pressure changes INDIRECTLYINDIRECTLY with variations is atmospheric pressureExplain……

Vapor pressure is a function of IMF’s within the liquid phaseStronger IMF’s = lower vapor pressureWeaker IMF’s = higher vapor pressure

VI. Acids and Bases

Acids = substances that react with a base; often has a low pH

May be strong or weak

Actual definition depends upon the type of acid/base

Bases = substances reacting with an acid; often has a high pH

May be strong or weak

3 major types of acids and bases here

Properties of Acids and Bases

Acids: Taste sour Conduct current in

solution React with bases to

form water and salt React with some

metals to make H2(g)

Low pH

Bases: Taste bitter Slippery/soapy

feeling Conduct current in

solution React with acids to

form salt water Have low pOH or

high pH

1. Arrhenius Acid/Base

Acid = substances that release hydrogen ions in aqueous solutions

proton donors

Ex.] HCl H+ + Cl-

Base = substances that release hydroxide ions in aqueous solutions

Hydroxide donors

Ex.] NaOH Na+ = OH-

2. Bronsted-Lowry Acid/Base

Acid = any substance that can donate hydrogen ions in solution Proton donors

Ex.]

HCl H+ + Cl-

Base = any substance that can accept hydrogen ions in solution

Proton acceptors

Ex.]

NH3 + H+ NH4+

Lewis Acids and Bases [non-Regents]

Acid = any species that can accept an electron pair from another species in solution

Ex.] H+ + NH3

Base = any species that can donate an electron pair to another species in solution

NH4+

Weak vs Strong acids and bases

STRONG acids/bases will completely dissociate [ionize] in solution

Ex.] HCl, HNO3, H2SO4, NaOH, KOH, etc.

WEAK acids/bases produce very few ions per molecule in solution

Ex.] vinegar, H3PO4, formic acid, citric acid, etc.

B. Conjugates

Acid/Base Conjugates = species that are formed in solution as a result of the dissociation of an acid or base

Ex.] HCl + NaOH Na+ + Cl- + HOH

Cl- is the conjugate base Na+ is the conjugate acid

Acid-Base Reactions

Acid + Base = Salt + water

Acids and bases neutralize each other

H+ + OH- H2O

C. pH and pOH

pH = the scale, 0-14, that defines the acidity or basicity of a solution Based on the concentration of hydrogen ions

0-6 = acid 7= neutral 8-14 = base

pOHpOH = the measure of the concentration of OH- ions in solution

Opposite of pH

Scale 0-14 0-6 = strong base 7= neutral 8-14 = acidic

Relating pH and pOH

pH + pOH = 14 always!

pH = -log[H+]

pOH = -log[OH-]

D. pH and pOH Calculations

Ex. 1] What is the pH of a solution containing 9.15 x 10-6 M H+?

Ex. 2] What is the pH of a solution containing [OH-] = 8.11 x 10-5 M in 350.mL of solution?

E. Indicators

Indicators = compounds that change color when the pH changes

Color changes indicate the pH of the solution!

Use several indicators to pinpoint the final pH!

Indicators: Table M

Find the pH using the indicator and its color in the solution…

Tutorial on indicators:

http://www.kentchemistry.com/links/AcidsBases/Indicators.htm

Expanded Indicators Chart

F. Titrations

Titration = method used to determine the pH of an unknown solution

Process to find the concentration of an unknown acid/base by neutralizing it with a base/acid of known concentration

An indicator signals the equivalence point and tells that the neutralization is complete

Titrations, [continued]

Uses burets, a standard solution of known pH, an indicator, and a fixed volume of a solution with an unknown pH

Titration Formula:

MaVa = MbVb