5.10 the chemistry of acids and bases

PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

Solutions

Unit 5

Lesson 10
The Chemistry of
Acids & Bases

1

01.

02.

03.

PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

What is pH and how is it used?

What is the difference between acids and
bases?

Essential Questions

2

What are common acids and bases found in
everyday life?

PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

Review Question

Draw the electron dot diagram for H2O

Warning: DHMO (Dihydrogen

Monoxide) is a colorless,

odorless chemical compound
known to accelerate corrosion,
short circuit electrical systems,

and cause suffocation. This

common chemical will combine

with sulfates and nitrates to

produce acid. The gaseous state

of DHMO has been known to

cause burns.

Draw a Hydrogen Atom –

include both the protons and electrons:

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PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

Review Question

Draw the electron dot diagram for H2O

Draw a Hydrogen Atom –

include both the protons and electrons:

H = 1 e- + 1 e- = 2 e-
H = 1 e- + 1 e- = 2 e-
O = 6 e- + 2 e- = 8 e-

Image Wikimedia Commons
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PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

Discussion: Are you an Acid, a Base, or Neutral?

In small groups discuss whether you think your personality

is an “acid”, a “base” or “neutral”, and why.

6

Poll

Is your personality more of an acid or a base?

• Acid

• Base

PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

The Power of Hydrogen (Cation and Hydronium)

Hydrogen is small but mighty!

Hydrogen

Cation

Hydrogen can give
away it’s one electron
to become a …

Hydronium

Ion

Hydrogen Cation
can be added to
water to become a …

Uh is it OK that I come to the

party without an electron?

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PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

The Power of Hydrogen (Hydroxide)

[OH]-

Hydroxide Ion

Although a single hydrogen can give one
electron to oxygen, this is not enough to
fill the outermost orbital with 8 electrons.
Thus, oxygen must get an extra electron
from somewhere else, making the entire
molecule a negative ion.

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PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

9

Hydrogen Cation, Hydronium Ion, Hydroxide Ion

Listening Activity

PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

10

Which Ion is Which?

Ion Name

Written As?

Hydroxide Ion

Hydronium Ion

Practice or Check

Match

Match the following

• Hydroxide ion

• Hydronium ion

• Water

OH-

H30+

H2O

• OH-

• H30+

• H2O

PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

11

Which Ion is Which?

Ion Name

Written As?

Hydroxide Ion

OH-

Hydronium Ion

H3O+

Practice or Check

Categorize

Options (6)

An acid is a molecule that donates a hydrogen ion [H+] when dissolved in H2O

A base is a molecule that produces a hydroxide ion [OH-] when dissolved in H2P

An acid is a molecule that accepts an electron

A base is a molecule that donates an electron

An acid is a molecule that donates a proton

A base is a molecule that accepts a proton

Organize these options into the right categories

Arrhenius

Lewis

Bronsted - Lowry

PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

Three Definitions of Acids & Bases (early 1920’s)

An acid is a molecule
that donates a
hydrogen ion [H+]
when dissolved in
H2O.

Arrhenius

Lewis

Bronsted-Lowry

An acid is a molecule
that accepts an
electron.

An acid is a molecule
that donates a proton.

A base is a molecule
that produces a
hydroxide ion [OH-]
when dissolved in
H2O.

A base is a molecule
that donates an
electron.

A base is a molecule
that accepts a proton.

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PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

Always in Two They Are

In an acid-base chemical reaction an
Acid + Base = Conjugate Base Pair

HCl + H2O ⇌[H3O]++ Cl-

Image Wikimedia Commons
13

PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

Always in Two They Are

HCl + H2O ⇌[H3O]++ Cl-

Conjugate

Acid

Conjugate

Base

Base

Acid

Hydronium

Ion

donated
the proton

Chloride

Ion

accepted
the proton

Water

accepts the

proton

Hydrogen
donates the

proton

Image Wikimedia Commons
14

PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

Water is both an acid and a base!

H2O + H2O ⇌[H3O]++ [OH]-

Conjugate

Acid

Conjugate

Base

Water can be an acid or a base!

Base

Acid

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PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

Water is both an acid and a base!

H2O + H2O ⇌[H3O]++ [OH]-

Conjugate

Acid

Conjugate

Base

Water can be an acid or a base!

Base

Acid

Water (you know, the stuff in your body and water bottle)
dissociates into ions in a fraction of a second but in the next
fraction of second reforms back into water (reversible).
The # of times this happens at any given moment is called
Kw which is 1 x 10-14.

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PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

Shorthand / Nicknames

H2O(l) ⇌H+

(aq)+ [OH]-

(aq)

H2O + H2O ⇌[H3O]++ [OH]-

is the same as

water dissolved in water

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PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

18

H2S + H2O ⇌H++ S2-

Can you identify the acid, the base, the conjugate acid, & conjugate base?

Practice or Check

PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

19

Can you identify the acid, the base, the conjugate acid, & conjugate base?

H2S + H2O ⇌H++ S2-

H2S = acid (donates proton)
H2O = base (accepts proton)

H+= conjugate acid (donated proton)
S2-= conjugate base (accepted proton)

Practice or Check

PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

pH Scale Revisited: The Power of Hydrogen

Image Wikimedia Commons

The pH scale is a negative logarithmic measure of H+ ions.

As you go up in pH, each # is 10x different than the number before.

10 1 = 10 ; 10 2 = 100, 103 = 1000, 104 = 10,000 and so forth.

The amount of H+ ions actually gets smaller as you go up the scale which is negative to

what you expect.

High H+ ions

Low H+ ions

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PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

Indicator Solutions

Image Flinn Scientific

The most common

indicator for acids and
bases is Litmus which
turns blue in a basic
solutions and red in

acidic solutions.

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PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

Indicator Solutions

Image Flinn Scientific

Many indicator
solutions have

different pH ranges in
which they react and
change colors. This
is because when they
give up H+ ions, the
indicator molecule
changes shape and

reflects light
differently.

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PHYSICAL SCIENCE | LESSON 5.10 | THE CHEMISTRY OF ACIDS & BASES

26

Acids and Bases

Listening Activity