ch. 15 solutions water is a ___________ molecule and therefore __________. water forms...

Ch. 15 Solutions• Water is a ___________ molecule and therefore __________.

• Water forms _______________ ________ which strongly bonds the molecules together with each other. These intermolecular bonds give water some very unique properties:

High surface tension: acts like a thin “________” on the surface.

• _______________ are used to reduce water’s surface tension so it can “wet down” a surface such as clothing.

“Water Strider”

bentpolar

hydrogenbonds

skin

Detergents

Surface Tension of Water

metal paper clip on water water forms “beads”

Water makes 6-sided (hexagonal) ___________ of ice or snow.

More Unique Properties of Water

Water readily dissolves other _____________ substances and ionic solids/salts.

crystals

polar

• There are two parts to a solution:

1) ____________- the dissolving medium which is typically a liquid or the substance in greater amount when 2 similar phases are mixed

2) _____________ - the substance that dissolves

Aqueous Solutions

Solvent

Solute

Examples of common solutions:

• Kool-aid = _________ in _______

• Air = ____ in ____

• 14K gold = _______ in _________

sugar water

O2 N2

silver gold

Examples of common solutions:

• __________ = copper in zinc

• Cola Drinks = sugar in water and ______ in ___________

Brass

CO2 water

• This phrase means that polar solvents dissolve __________ solutes and nonpolar solvents dissolve ___________ solutes.

Example: Mix together water, oil, table salt, and iodine (I2).

What dissolves in what? ________________

____________________________________

____________________________________

____________________________________

“Like Dissolves Like”

polarnonpolar

The nonpolar oil will dissolve the nonpolar I2

and the water dissolves the salt since they are

both polar.

“Like Dissolves Like”

nonpolar grease remover

“Like Dissolves Like”

Vinegar & oil dressing will separate. Shake well before using!

Solution Vocabulary

• _______________ : two liquids that can dissolve in each other

Example: ____________ in water

•_________________ : the liquids don’t mix

Example: _____ and water

Miscible

Immiscible

alcohol

Oil

Factors that Affect Solubility

Tested Dissolved Oxygen, Conductivity, Salinity (salt concentration), and Temperature.

Factors that Affect Solubility

Tested Dissolved Oxygen, Conductivity, Salinity (salt concentration), and Temperature.

Factors that Affect Solubility

Tested Dissolved Oxygen, Conductivity, Salinity (salt concentration), and Temperature.

Measuring the Concentration of a Solution

• ___________________: how much solute is dissolved in a certain amount of solvent at some given temperature and pressure.

Qualitative Vocabulary

• _______________ : contains a small amount of solute

• _______________ : contains a large amount of solute

concentrated dilute

Concentration

Dilute

Concentrated

Quantitative Vocabulary:• ____________: moles of solute per liter of solution

• _______________ ( ) = moles of solute ÷ Liters of solution

Practice Problem: What is the molar concentration of an aqueous NaCl solution when 25.0 grams are dissolved in water to make 500 mL of solution?

Molarity

Molarity M

25.0 g x ________________ =

Molarity = 0.855 M

M = ___________________

1 mol

58.5 grams0.427 mol

0.427 mol

0.500 L

Making a Solution of a Required Concentration

# of moles ÷ # of liters = Molarity

Making Dilutions

• Dilution: Making a solution _______ concentrated by ________ more ___________ .

Important: When diluting acids:

“Add acid to water, do as you ought-er.”

M1xV1=M2xV2

M1 -- the initial concentration of the solution.

V1 -- the initial volume of the original solution that is going to be diluted with water.

M2 -- the final concentration of the solution after it’s diluted with water.

V2 -- the total volume of the final solution after it has been diluted with water.

less addingsolvent

Making Dilutions

M1xV1=M2xV2

Practice Problems:

1) The science department buys HCl in large bottles that have a concentration of 12 Molar. The science teacher then dilutes the acid for labs. How would the teacher make 2.0 liters of a 2.5 M HCl solution from this “stock” solution?

2) What is the final concentration of a sugar solution if 300 mL of water is added to 500 mL of a 2.5 M sugar solution?

( ) ( ) = ( ) ( )

V1 = 0.417 L

( ) ( ) = ( ) ( )

M2 = 1.56 M

12 M V1 2.5 M 2.0 L

Take 0.417 L of the stock solution and add it to some water and then add enough water to make a final volume of 2.0 liters.

2.5 M 500 mL 800 mLM2

Calibration Curves• A standard solution is a solution of__________________. These

solutions can be used to predict properties of an unknown solution.

• At least _________ data points are used and then plotted with a line of best fit.

known concentration

three

Beer’s Law

Calibration Curves

• If spectrometer reads the absorbance at 0.48 what is the molarity?

• What would you predict the absorbance of a 7M solution to be?

3.12 M

0.62

Ch. 20 Notes -- Acids and Bases What makes something an acid?

Acid Properties:

(1) tastes _______-- _______________

(2) corrosive to _________

(3) contains [ ___ ] (or [ _____ ] = “_______________” ions)

(4) proton ([ ___ ]) __________-- Brønsted-Lowry Theory

Example: HCl + H2O ______ + ______

sour lemons

metals

H+ H3O+ hydronium

H+ donor

Cl− H3O+

Properties of BasesWhat make something a base?

Base Properties: (…the opposite of acid properties)

(1) tastes ________ -- ___________ peel , parsley, dark chocolate

(2) feels _____________ -- ________

(3) contains [ _____ ] ions

(4) proton ([H+]) ______________-- Brønsted-Lowry Theory

Example: NH3 + H2O ______ + _______

bitter banana

slippery soap

OH−

acceptor

NH4+ OH−

Examples of Common Acids:

• Pepsi, _________ juices, ___________, stomach acid, battery acid, _____________, ______

citrus aspirinvinegar DNA

Common Bases

Common Bases• Examples of Common Bases: milk of magnesia, ___________,

drain cleaner, soap, blood, ____________ tablets, ___________ ________.

ammonia

antacid bakingsoda

Indicators• An indicator is a chemical that will change ___________ when

placed in an acidic, basic or neutral environment.

Indicator Colors For Acids

• litmus paper = _______

• phenolphthalein = ___________

• red cabbage juice (universal indicator) = ________

• methyl orange = _______

colors

red

clear

red

red

Indicator Colors for Bases• litmus paper = _______

• methyl orange = ____________

• red cabbage juice (universal indicator) =________

• phenolphthalein = ______

Acid Base

phenolphthalein

blue

yellow

blue

pink

Universal pH Paper : Indicator Colors

Acidic

Basic

Neutral

Acid Vocabulary• strong acid - readily ___________ to produce ______ [H+] ions in

water

Examples: _________, HNO3, _______

• weak acid - produces a __________ amount of [H+] ions when in water

Examples: HC2H3O2 (vinegar) , _________, _________

dissociates many

HCl H2SO4

small

H2CO3 lemon juice

• strong base- readily __________ to produce ______ [OH−] ions in water

Examples: NaOH , ________

• weak base- produces a __________ amount of [OH−] ions when in water

Examples: _____ (ammonia); Mg(OH)2 (milk of magnesia)

Other Vocabulary

• _______________- another term for basic solutions

• _______________- a substance that can act as both an acid and a base

Examples: ___________ , ____________

dissociate many

KOH

small

NH3

Alkaline

Amphoteric

H2O HCO3−

Base Vocabulary

Measuring the Amount of H+ and OH− Ions in a Solution

• _____ Scale- measures the _____________ of [H+] ions in a solution

• _____ Scale- measures the concentration of [ ____ ] ions in a solution

Formulas

pH = − (log [H+]) pOH = −(log [OH−])

[H+] = 10−pH [OH−] = 10−pOH

[H+] x [OH−] = 1 x 10−14 pH + pOH = 14

• With the pH scale, we have another way to define acids and bases:

Acids have a pH _________7.0

Bases have a pH _________7.0

Neutral pH ___7.0

pH concentration

pOH OH−

below

above

=

pH Testing

Alkalinity Testing

Practice Problems:

1) Calculate the pH of a 0.001 M HCl solution

2) What is the pH of a 4 x 10-9 M KOH solution?

3) What is the concentration of [H+] ions in a NaOH solution with a pH of 8.50?

4) What is the concentration of [H+] ions in a HNO3 solution with a pH of 1.50

[H+] = 0.001 M So…pH = − (log 0.001 M) pH = 3

[H+] = 10−pH [H+] = 10−8.5 Molar or 3.16 x 10−9 M

[H+] = 4 x 10-9 M So…pH = − (log 4 x 10-9 M) pH = 8.3

[H+] = 10−pH [H+] = 10−1.5 Molar or 0.0316 M

Neutralization Reactions

When an acid and base are mixed, the reaction produces _______

and ___________.

• If the initial concentrations and volumes of the reactants are equal, the products will be ____________... (pH= 7.0)

• All neutralization reactions are ___________ replacement reactions.

HX + M(OH) ______ + ______

salt

water

neutral

double

MX H2O(“Salt”)

Titration• Mixing an acid with a base to

determine a __________________ is called “titration.”

• An ____________ is used to determine when neutralization has occurred.

• ________________ Solution - the solution of known concentration

• ______ _________ - the point of neutralization when titrating

• At the ______ point, the moles of [H+] ions = moles of [OH−] ions.

concentration

indicator

Standard

End Point

end

(Macid)x(Vacid) = (Mbase)x(Vbase)

Practice Problems:

(1) A 25 mL solution of HNO3 is neutralized by 18 mL of 1.0 M NaOH standard solution using phenolphthalein as an indicator. What is the concentration of the HNO3 solution?

(2) How many mL of 2.0 M KOH will it take to neutralize 55 mL of a 0.76 M HCl standard solution?

Determining the Concentration of an Acid (or Base) by Titration

( ) x ( ) = ( ) x ( )

( ) x ( ) = ( ) x ( )

Macid 25 mL 1.0 M 18 mL

Macid = 0.72 Molar

0.76 M 55 mL 2.0 M Vbase

Vbase = 20.9 mL