The document discusses the definitions, properties, and theories of acids and bases, including Arrhenius, Bronsted-Lowry, and Lewis theories. It covers the chemical reactions involving acids and bases, examples of common acids and bases, and the concepts of acid and base strength. Additionally, it explains the pH scale and how to measure acidity and basicity in solutions.

1. Copyright Sautter 2015

2. ACIDS, BASES & SALTS
WHAT IS AN ACID ?
WHAT IS A BASE ?
WHAT ARE THE PROPERTIES OF
ACIDS AND BASES ?
WHAT ARE THE DIFFERENT KINDS
OF ACIDS AND BASES ?
HOW ARE ACIDS AND BASES
NAMED?

3. PROPERTIES OF ACIDS
• CONTRARY TO COMMON BELIEF ACIDS DO NOT
ATTACK ALL SUBSTANCES. MANY ARE VITAL TO
OUR VERY EXISTENCE !
• ALL ACIDS DO HOWEVER HAVE SEVERAL
COMMON CHARACTERISTICS.
• (1) ACIDS TASTE SOUR
• (2) ACIDS TURN LITMUS RED (LITMUS IS A DYE
THAT CHANGES COLOR DEPENDING ON ACIDITY)
• (3) ACIDS REACT WITH ACTIVE METALS TO FORM
HYDROGEN GAS
• (4) ACIDS REACT WITH BASES TO FORM SALTS
AND WATER
I’VE GOT
TOO MUCH
HCl !
3

4. PROPERTIES OF BASES
• (1) BASES TASTE BITTER (MEDICINES ARE OFTEN
BASES THUS THE TERM “BITTER MEDICINE”)
• (2) BASES TURN LITMUS BLUE
• (3) BASES FEEL SLIPPERY
• (4) BASES REACT WITH ACIDS TO FORM SALTS
AND WATER
4

5. DEFINITION OFACIDS AND BASES
• ACIDS AND BASES AND THE REACTIONS WHICH
RESULT CAN BE DESCRIBED USING SEVERAL
DIFFERENT THEORIES.
• THE THREE MOST COMMON THEORIES ARE:
• (1) THE ARRENHIUS OR TRADITATIONAL THEORY
• (2) THE BRONSTED – LOWRY THEORY
• (3) THE LEWIS THEORY
• EACH OF THE THREE THEORIES VIEW ACIDS AND
BASES SLIGHTLY DIFFERENTLY BUT THEY DO
NOT CONTRADICT EACHOTHER IN ANY WAY.
ONE MERELY EXPANDS ON THE OTHER !
5

6. THE ARRENHIUS OR TRADITIONAL
ACID – BASE THEORY
• AN ACID IS A SUBSTANCE WHICH RELEASES HYDROGEN
IONS (H+) IN SOLUTION.
• HNO3(aq)  H+
(aq) + NO3
-
(aq)
• A BASE IS A SUBSTANCE WHICH RELEASES HYDROXIDE
IONS (OH-) IN SOLUTION.
• NaOH(S)  Na+
(aq) + OH-
(aq)
• WHEN AN ACID AND BASE REACT (A REACTION CALLED
NEUTRALIZATION), A SALT AND WATER ARE FORMED.
• HNO3(aq) + NaOH(aq)  NaNO3(aq) + H2O(aq)
(acid) (base) (salt) (water) 6

7. COMMON ACIDS & BASES
• HYDROCHLORIC ACID (STOMACH ACID) – HCl
• ACETIC ACID (VINEGAR) – HC2H3O2
• CARBONIC ACID (SODA WATER) – H2CO3
• SODIUM HYDROXIDE (DRAINO) – NaOH
• AMMONIA WATER (CLEANING AGENT) – NH4OH
• ALUMINUM HYDROXIDE (ROLAIDS) – Al(OH)3
7

8. THE BRONSTED – LOWRY ACID AND
BASE THEORY
• AN ACID IS A PROTON DONOR. A PROTON IN SOLUTION
CONSISTS OF A HYDROGEN ION (H+). (HYDROGEN WITH
AN ATOMIC NUMBER OF ONE AND A MASS NUMBER OF
ONE HAS ONE PROTON, NO NEUTRONS AND AFTER
LOSING ONE ELECTRON TO FORM AN ION, HAS NO
ELECTRONS.)
• A BASE IS A PROTON ACCEPTOR AND IT NEED NOT
CONTAIN HYDROXIDE IONS.
• AN ACID – BASE REACTION CONSISTS OF A PROTON
TRANSFER FROM AN ACID TO A BASE. WHEN THIS
OCCURS A NEW ACID AND BASE ARE FORMED. THIS IS
BRONSTED- LOWRY NEUTRALIZATION.
• HCl(aq) + H2O(aq)  H3O+
(aq) + Cl-
(aq)
(acid) (base) (new acid) (new base)
8

9. A CLOSER LOOK AT BRONSTED –
LOWRY ACID – BASE REACTIONS
(1) WATER CAN ACT AS A BASE. AT TIMES IT CAN EVEN ACT AS A
ACID.. THE TERM IS AMPHIPROTIC MEANS THAT IT CAN BE EITHER
DEPENDING ON THE SITUATON.
(2) WHEN WATER ACTS AS A BASE H3O+ ION IS FORMED. THIS CALLED
HYDRONIUM ION.
(3) THE ORIGINAL BASE (H2O) AFTER RECEIVING THE PROTON CAN
NOW FUNCTION AS AN ACID IN THE REVERSE REACTION.
HYDRONIUM ION IS CALLED THE CONJUGATE ACID OF THE BASE
WATER IN THIS REACTION.
(4) THE ORIGINAL ACID (HCl)AFTER LOSING THE PROTON CAN NOW
FUNCTION AS AN BASE IN THE REVERSE REACTION. CHLORIDE ION
IS CALLED THE CONJUGATE BASE OF THE ACID HYDROCHLORIC
ACID IN THIS REACTION.
HCl(aq) + H2O(aq)  H3O+
(aq ) + Cl-
(aq)acid base conjugate acid conjugate acid
9

10. LEWIS ACID – BASE THEORY
• THE LEWIS ACID – BASE THEORY EXPANDS THE
ARRENHIUS AND BRONSTED LOWRY THEORIES TO
INCLUDE EVEN MORE SUBSTANCES WHICH HAVE BEEN
FOUND EXPERIMENTALLY TO BE ACIDIC OR BASIC BUT
NOT COMPLETELY EXPLAINED BY EITHER.
• THE LEWIS THEORY DESCRIBES ACIDS AS ELECTRON
PAIR ACCEPTORS AND BASES AS ELECTRON PAIR
DONORS. AS A RESULT THE OBSERVED ACIDIC
PROPERTIES OF METAL IONS IN SOLUTION CAN BE
EXPLAINED.
• ADDITIONALLY, THE BASIC PROPERTIES OF SUBSTANCES
SUCH AS AMMONIA CAN AS BE EXPLAINED AS
ELECTRON PAIR DONORS EVEN THOUGH AMMONIA
CONTAINS NO HYDROXIDE IONS.
10

11. WHERE DO ACIDS & BASES COME FROM?
• ACIDS RESULT FROM THE ADDITION OF NONMETAL
OXIDES TO WATER. THESE OXIDES ARE CALLED ACID
ANHYDRIDES (ACIDS WITHOUT WATER). EVEN
CARBON DIOXIDE WHEN ADDED TO WATER WILL
MAKE THE SOLUTION MILDLY ACIDIC.
• CO2(g) + H2O(l)  H2CO3(aq) (CARBONIC ACID)
• SO2(g) + H2O(l)  H2SO3(aq) (SULFUROUS ACID)
• BASES ARE FORMED BY METALLIC OXIDES AND
WATER. THEY ARE CALLED BASIC ANHYDRIDES.
• CaO(s) + H2O(l)  Ca(OH)2(s) (CALCIUM HYDROXIDE)
• Na2O(s) + H2O(l)  2 NaOH(s) (SODIUM HYDROXIDE)
11

12. ACID & BASE STRENGTH
• WHEN DISSOLVED SUBSTANCES SEPARATE INTO
FREE MOBILE IONS THIS IS CALLED
DISSOCIATION.
• THE STRENGTH OF ACIDS AND BASES DEPENDS
ON THEIR ABILITY TO DISSOCIATE IN SOLUTION.
• CONCENTRATION REFERS TO THE MOLARITY OF
THE SOLUTION.
• CONCENTRATION AND STRENGTH DO NOT MEAN
THE SAME THING BUT ARE RELATED.
• THERE ARE SEVERAL STRONG ACIDS AND BASES.
THESE DISSOCIATE WELL (~ 100%). ALL OTHER
ACIDS AND BASES ARE WEAK (DISSOCIATE
POORLY)
12

13. COMMON STRONG ACIDS
• STRONG ACIDS
• HCLO4 PERCHLORIC ACID
HI HYDROIODIC ACID
HBr HYDROBROMIC ACID
HCl HYDROCHLORIC ACID
HNO3 NITRIC ACID
H2SO4 SULFURIC ACID
13

14. COMMON STRONG BASES
• STRONG BASES
• LiOH LITHIUM HYDROXIDE
• NaOH SODIUM HYDROXIDE
• KOH POTASSIUM HYDROXIDE
• RbOH RUBIDIUM HYDROXIDE
• CsOH CESIUM HYDROXIDE
• Ca(OH)2 CALCIUM HYDROXIDE
• Sr(OH)2 STRONTIUM HYDROXIDE
• Ba(OH)2 BARIUM HYDROXIDE 14

15. PH OF SOLUTIONS
• PH IS A CONVENIENT SYSTEM FOR THE MEASURING THE
ACIDITY OF A SOLUTION.
• PH IS DEFINED AS THE NEGATIVE LOGARITHM OF THE
HYDROGEN ION CONCENTRATION IN A SOLUTION.
• A LOGARITHM (LOG) IS A POWER OF 10. IF A NUMBER IS
WRITTEN AS 10X THEN ITS LOG IS X.
• FOR EXAMPLE 100 COULD BE WRITTEN AS 102
THEREFORE THE LOG OF 100 IS 2.
• IN CHEMISTRY CALCULATIONS OFTEN SMALL NUMBERS
ARE USED LIKE .0001 OR 10-4. THE LOG OF .0001 IS
THEREFORE –4.
• FOR NUMBERS THAT ARE NOT NICE EVEN POWERS OF 10
A CALCULATOR IS USED TO FIND THE LOG VALUE. FOR
EXAMPLE THE LOG OF .00345 IS –2.46 AS DETERMINED
BY THE CALCULATOR. 15

16. PH OF SOLUTIONS (CONT’D)
• PH = - LOG [H+]
• P MEANS NEGATIVE LOG AND THE
BRACKETS AROUND H+ MEANS
“CONCENTRATION OF H+”
SAMPLE PROBLEM:
WHAT IS THE PH OF A SOLUTION WHEN ITS
[H+] = 0.000001 M ?
SOLUTION:
0.000001 = 10-6
PH = - LOG (10-6) = - ( -6.00) = 6.00
16

17. THE PH SCALE
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
ACID RANGE BASE RANGE
NEUTRAL
LOW PH VALUES INDICATE HIGH ACIDITY
HIGH PH VALUE INDICATE HIGH BASITY
7.00 IS THE PH OF PURE WATER
PH , [H+] AND [OH-]
PH , [H+] AND [OH-]
[H+] = 1.00 x 10-7 M IN PURE WATER
PH = - LOG (1.00 x 10-7) = 7.00
17

18. POH OF SOLUTIONS
• POH = - LOG [OH-]
• WHERE THE BRACKETS AROUND OH-
MEANS “CONCENTRATION OF OH-”
• SAMPLE PROBLEM:
• WHAT IS THE POH OF A SOLUTION WHEN
ITS [OH-] = 0.00001 M ?
• SOLUTION:
• 0.00001 = 10-5
• POH = - LOG (10-5) = - ( -5.00) = 5.00
• PH + POH = PKw = 14.0
• PH = 14.0 –5.0 = 9.0, THE SOLUTION IS
BASIC
18

19. FORMATION OF A HYDROGEN ION
(AN AQUEOUS PROTON)
1 P+
0 N0
1e-
A HYDROGEN ATOM
LOSES ITS ELECTRON
TO FORM A
HYDROGEN ION
Atomic number
1
Atomic mass
1
19

20. STRONG & WEAK ACID
DISSOCIATION
STONG ACIDS DISSOCIATE READILY
(NITRIC ACID HNO3)
WEAK ACIDS DISSOCIATE POORLY
(HYDROFLOURIC ACID HF)
FREE MOBILE IONS
READILY FORM
ALL MOLECULES
DISSOCIATE
FREE MOBILE IONS
FORM BUT WITH
DIFFICULTLY
FEW MOLECULES
DISSOCIATE 20

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