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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