Acids and Bases
Standard 5
Chapter 19
Mr.O’Brien
SFHS
Properties of
Acids and Bases (std.5.A)

Major Properties
 Acids
 Taste sour
 Burning feeling
Reacts w/ metals
Reacts w/ carbonates (-CO3)
Like sodium, magnesium, zinc
Like NaHCO3 (baking soda)
Produces H2
(hydrogen gas)
Produces CO2
(carbon dioxide gas)

Bases
 Taste bitter
 Feels slippery
(figure 1) The image above (left) shows the
 Examples include mostly cleaners. reaction between acid and baking soda
(NaHCO3) producing a gas. The image
above (right) shows the reaction of acid and
various metals producing hydrogen gas.
Properties of Acids and Bases
(cont.) (std.5.A)


Both produces electrolytes
 electrolytes are liquids that contain ions allowing it
to conduct electricity.
Acidic, basic, and neutral solutions are based on the
concentration (amount) of [H+] and [OH-] in an
aqueous solution.
 Acidic solutions contain more H+ than OH Neutral solutions contain equal # of H+ and OH Basic solutions contain more OH- than H+.
(figure 1) The light bulb is able
to light because IONS are FREE
to MOVE in the solution and thus
carry electricity.
(figure 2) The images below shows ions in a
solution. Acids/bases can conduct electricity
because they produce [H+] ions or [OH-] ions.
Properties of Acids and Bases
(cont.) (std.5.A)

Acid and Bases can be identified by many ways:
 Litmus paper.
 blue litmus paper turns red w/ acid.
 red litmus paper turns blue w/ base.
 Universal indicators


test for a wide range of acid to bases
“Cabbage Juice”
Properties of Acids and Bases
(cont.) (std.5.A)

Both produce Salts when reacted with each
other

Neutralization reaction:

An acid and a base react to form a salt and water.

Salt: any ionic compound (metal & non-metal)
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
ACID
BASE
SALT
(figure 1) The animation shows a
neutralization reaction.
(figure 2) Antacids such as Tums,
etc. perform neutralization
reactions in the stomach.
Properties of Acids and Bases
(cont.) (std.5.A) HONORS
Checking for Understanding
Write the Neutralization Reactions for the following Acid
& Bases:
Hints
•
Make sure you write correct
formulas.
•
Make sure you balance equations.
HCl reacts with KOH
HCl(aq) + KOH(aq) → KCl(aq) + H2O(l)
H2S reacts with LiOH
H2S(aq) + 2LiOH(aq) → Li2S(aq) + 2H2O(l)
HBr reacts with Mg(OH)2
2HBr(aq) + Mg(OH)2(aq) → MgBr2(aq) + 2H2O(l)
HClO reacts with NaOH
HClO(aq) + NaOH(aq) → NaClO(aq) + H2O(l)
(figure 1) The image above
shows acid buildup in the
stomach. Antacids prevent the
acid buildup by neutralizing the
acid producing salt and water.
Key Terms
Bronsted-Lowry Model
of Acids & Bases (std.5.B)
Dissociate
(to separate into ions)
Hydroxide ion
[OH-]
(when water loses a [H+])
How do Acids & Bases Behave?
 ACIDS
 substances that are hydrogen-ion donors.
Hydronium ion
[H3O+] = [H+]
(when water gains a [H+])
HCl + H2O ⇨Cl- + H3O+
acid

Hydronium
ion
Base
 substances that are hydrogen-ion acceptors.
base
Conjugate
(what the acid or base turns into)
Hydroxide ion
NH3 + H2O  NH4 + OH+
How to write the dissociation of an Acid or Base?
 Water is always added to an acid or base
HF + H2O ⇨ H3O+ +
conjugate
acid
Fconjugate
base
Bronsted-Lowry Model of
Acids & Bases (cont.) (std.5.B)
Checking for Understanding
1. Show the movement of [H+] between the reactants and products
2. Identify the acid & bases.
3. Identify the conjugate pairs
conjugate
acid
conjugate
base
ACID
BASE
conjugate
acid
conjugate
acid
conjugate
base
conjugate
base
Bronsted-Lowry Model of
Acids & Bases (cont.) (std.5.B)
Checking for Understanding
1. Write a chemical equation showing the dissociation of the following acid or base.
2. Identify the acid & bases.
3. Identify the conjugate pairs.
conjugate
base
ACID
H3PO4 (acid)
H3PO4 + H2O → H3O+ + H2PO4conjugate
base
ACID
HSO4- (acid)
HSO4- + H2O → H3O+ + SO4-2
conjugate
acid
BASE
CN- (base)
CN- + H2O → OH- + HCN
BASE
C2H3O2- (base)
conjugate
acid
C2H3O2- + H2O → OH- + HC2H3O2
Arrhenius Model
of Acids and Bases (HONORS)
(std.5e)

Acids are compounds that contains
hydrogen which then dissociates to form
hydrogen ions (H+)


HCl(g) → H+(aq) + Cl-(aq)
Bases are compounds that contains
hydroxides and dissociates to form hydroxide
ions (OH-)

NaOH(s) → Na+(aq) + OH-(aq)
Strengths of Acids/Bases
(std.5c)
Key Terms
Ionize
(to separate into ions)
What is a STRONG acid?
 Acids that completely ionize in aqueous
HX + H2O ⇨ H3O+1 + X-1
Strong acid/bases PRODUCES weak conjugate base/acid
What is a weak acid?
 Acids that partially ionize
HX + H2O  H3O+1 + X-1
Weak acid/base PRODUCES strong conjugate base/acid

The same concept applies to bases.
 NaOH + H2O→ OH- + Na+ strong base
 NH3 + H2O  NH4+ + OHweak base
Checking for Understanding
1. What type of acid would be a better
ELECTROLYTE? Explain your answer.
2. Compare strong & weak acids in terms of
their DISSOCIATION.
Checking for Understanding
1. Hypothesis which might be the
stronger acid. Explain your answer.
Strengths of Acids/Bases (cont.) (std.5c)
Strong Acids
HCl
H2SO4
STRONG acid
weak acid
•Acid completely dissociates
into ions [H+] & [A-]
•Forms great electrolytes
•Acid partially dissociates into ions
[H+] & [A-] and contains (non-ionized)
molecules.
•Forms poor electrolytes
(figure 1) (a) strong acid produce mostly
ions, (b) weak acids produce a mixture of
molecules and ions.
Checking for Understanding
1. An acid is highly ionized in aqueous
solution. Is the acid strong or weak?
Explain your reasoning.
1. Why is a strong base such as sodium
hydroxide (NaOH) generally not
considered to have a conjugate acid?
1. HCl is a strong acid, CH3COOH is a weak
acid. Which one would be a better
electrolyte. Explain. Which will allow a
light bulb to glow more brightly?
Strong Bases
NaOH
Ca(OH)2
Weak Acids
CH3COOH
HCN
Weak Bases
NH3
CH3NH2
The pH Scale (std.5d)

pH scale easier way to express [H+] (acidity).


pH scale is 0-14
A change of 1 pH unit represents a 10x change in [conc.]

(pH = 3) has 10x more H+ than (pH = 4)
Checking for Understanding
1. Identify the resulting solutions based on the following:
 a STRONG acid is mixed with a STRONG base.
 a STRONG acid is mixed with a weak base.
 a weak acid is mixed with a STRONG base.
1. Identify the difference in [H+] ion between each solution:
 tomatoes & milk
 lemon juice & saliva
 bleach & liquid drain cleaner
Remember
A higher
than [OH-] is acidic.
A higher [OH-] than [H+] is basic.
Stronger acids have lower pH values.
Stronger bases have higher pH values.
[H+]
Buffers (Honors)

Buffers: solutions that resist
changes in pH when limited
amounts of acid or base are
added.

Ex: adding 0.001mol of HCl to 1L of
pure H2O lowers pH from 7 to 2.
Adding 0.01mol of NaOH to 1L of
pure H2O increase pH from 7-12.
Adding the same amount of HCl or
NaOH to a buffer solution, pH might
not change by more than 0.1.