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−

Content Goal: Students will test pH to determine if household substances are an acid or a base.

Language Goal: Students will show they know the material by filling out the paper that will be

completed in class todaySocial Goal: Students will work together safely

and will follow instructions so that everyone has equal access to lab materials.

pH of food

SafetyNo play fighting or any touching. Move around the room in numerical order.Please keep the beakers on the table. Do

not move the beakers to you, move to the beakers.

Place used test strips into the waste beaker.

Wash your hands after the lab.

Examples of Common Acids:

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

citrus aspirinvinegar DNA

Common Acids

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

Self-Ionization of Water• Pure water is _____________. It can ionize itself to form OH− and

H3O+ ions in __________ amounts.

H2O + H2O H3O+ + OH−

(or H2O _______ + _______ )

• The universal indicator color is ___________ in neutral solutions.

neutralsmall

H+ OH−

green

self-ionization of water

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) a) Calculate the pH of a 0.001 M HCl solution

b) What is the pOH of this solution?

c) What is the concentration of [OH−] ions in the solution?

2) a) Calculate the pOH of a NaOH solution that has a pH of 8.50

b) What is the [OH−] of this solution?

c) What is the concentration of [H+] ions in the solution?

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

pH + pOH = 14 So…14 − 3 = pOH pOH = 11

[OH−] = 10−pOH [OH−] = 10−11 Molar or 1 x 10−11 M

So…14 − 8.5 = pOHpH + pOH = 14

[OH−] = 10−5.5 Molar or 3.16 x 10−6 M[OH−] = 10−pOH

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

pOH = 5.5

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