1. 14. Acids & Bases
chapter 10

2. Acids/Bases - by Physical Phenomena
Method
Acids
Taste
Feel
Effect on metals
Sour
n/a
Liberates H2 on reaction with iron, zinc & tin
Bitter
Slippery
n/a
Effect on indicators
Litmus
Phenolphthalein
Red
Colourless
Blue
Red

3. Lime(CaO) is the cheapest and most widely used commercial base (~18 billion kgs/yr in NA).
Made by heating limestone (CaCO3) to drive off CO2
heat CaCO CaO CO2
used for mortar and cement
Also to 'sweeten' acidic(sour) soils NB. Blue / pink lupins; 'natural' indicators for soil pH.

4. Acids/Bases - by Chemical Structure
Definition
Acids
Bases
1) Arrhenius
Generates H in water
Generates OH in water
2) Bronsted Lowry
Transfers H to a base
Accepts H+ from an acid
3) Lewis electron acceptor electron donor
NB: H+ = proton OH- = hydroxide ion

5. Bronsted -Lowry definition:
an acid is any substance that can transfer a proton to another substance
a base is a substance that can accept a proton

6. HCl H+ + Cl- CH3COOH H+ + CH3COO- H2O H+ + OH-
A strong acid ionizes completely and irreversibly in water, often 'inorganic', eg. hydrochloric acid A weak acid ionizes reversibly and therefore only partially, often 'organic', eg. acetic acid.
HCl H Cl-
CH3COOH H CH3COO-
H2O H OH-

7. In neutralization an acid and a base react to produce a solution that’s neither acidic nor basic.
A salt is a compound (other than water ) produced by the reaction of an acid with a base.

8. H
(+) H
(-) .. .. .. .. . . . . . . . . . . . . . . . . H N H Cl H N H Cl .. .. .. .. H H
Hydrogen
Ammonia
Ammonium
chloride
chloride
Base acid salt (+ water)
Na OH H Cl Na+Cl H2O
sodium
hydrogen
sodium
water
hydroxide
chloride
chloride

9. Typical Inorganic Acids (mostly 'strong')
Formula H3BO3 HIO3 HNO3 HClO4 H3PO4 H2SO4 HCl
Name Boric Iodic Nitric Perchloric Phosphoric Sulfuric Hydrochloric
Applications antiseptic, eye drops disinfectant fertilizers, explosives, dyes plating metals, explosives fertilizers, food additive fertilizers, paper, drugs cleaning metals/concrete
'weak' inorganic acids often end in '-ous', eg. nitrous-HNO2, sulfurous-H2SO3

10. Typical Organic Acids (usually 'weak')
Formula HCOOH HOCOOH CH3COOH CH3CH2COOH CH3CH(OH)COOH HOC(CH2COOH) COOH HO(CH2)3COOH
Name formic carbonic acetic propionic lactic citric hydroxyBA benzoic
Use bee/ant stings CO2 in H2O vinegar sweat, Sw. cheese muscle stress citrus fruit 'date rape' drug preservative
-COOH

11. ‘Foody’ Acids are Weak
Fortunately!

12. Typical Bases
Organic bases are the amines, R-N ie. carbon containing derivatives of ammonia, NH3
Inorganic bases can be 'strong' or 'weak', eg ) the 'hydroxide' derivatives of the alkali & alkaline earth elements, ie. rows 1,2 (3) of periodic table, are always strong eg. sodium / calcium hydroxide(NaOH, Ca(OH)2) 2) ammonia (NH3) is weak ) salts of strong bases & weak acids are 'weak', eg. sodium bicarbonate(NaHCO3), calcium carbonate(CaCO3)

13. Ammonia in water NH3 +H2O -> NH4 OH (ammonium hydroxide)
A source of OH-, hence a base
But a weak base since only partially dissociated (about 1%)

14. Lots of Strong Bases around the House !

15. Typical Salts Acid Base Salt HI + KOH KI + H2O hydrogen potassium
iodide
hydroxide
iodide(Iodized salt)
H2SO Mg(OH) MgSO H2O
sulfuric
magnesium
magnesium
acid
hydroxide
sulfate(Epsom salts)
H2CO Ca(OH) CaCO H2O
carbonic
calcium
calcium
acid
hydroxide
carbonate(Tums)
MSG = HOOC-CH2-CH2-CH(NH2)-COO- Na+

16. Water = Neutral (unless helped)
H2O H OH-
Only 1 in 500 million! NB. [H+] = [OH-] .. .. + . . . . H . O . H + H+ H O H . . .. .. H
hydronium ion
2H2O H3O OH-
hydronium ion

17. pH - the universal symbol for acidity
pH, the symbol for acidity, represents the 'power of the Hydrogen (or Hydronium) ion'.
The letter 'p' begins the English word power, the French word puissance, the German word potenz.

18. The pH of a solution is a measure of the acidity of that solution.
pH = - log[H3O+] or [H+]
pH = the negative logarithm of the proton (hydronium ion) concentration(= [ x ] ) (as Molarity = moles/Liter).
Don't panic! write the [H+] as a power of use the exponent of reverse its sign

19. pH of (neutral) Water Molarity (moles/L) of the proton(hydronium ion).
[H3O+] or [H+] = M = 1 x 10-7 M
(and [OH-] must also = 1 x 10-7M)
If pH = - log[H3O+]
Express conc'n. as power of = - log(10-7)
Use the exponent of = -7
Reverse the sign = +7
Then the pH of neutral water is 7

20. The pH of an acidic solution is less than 7
The pH of a neutral solution equals 7
The pH of a basic solution is greater than 7
For every tenfold increase in the [H3O+] conc’n. there is a decrease of one unit in the pH
For every tenfold decrease in the acidity there is an increase of one unit in the pH

21. Acidity and pH

22. Ex.1: The pH of 0.01 M HCl in water
HCl H Cl-
0.01M
0.01M
0.01M
Since HCl is a strong acid, ie. completely ionized in water, the [H3O+] = 0.01 M = 1 x10-2M Take the 'exponent' of 10, ie. -2, and reverse the sign, ie The pH of this solution must be 2.

23. Ex.2: The Basic Egg
Fresh eggs have a [H30+] = M.
What is the pH of a fresh egg?
Convert : [H+] = 10-8 M = [H3O+] Take the exponent of 10: Reverse the sign: A common pH for a fresh egg is 8.

24. Ex.3: How Acidic is a SopHt Drink?
A typical pH of a soft drink is What is the [H3O+] for a soft drink ?
In this case we reverse the process.
Since the pH is 3, the appropriate exponent of must be the 'reverse' of +3, ie Hence the [H3O+] or [H+] must = 10-3M = M for a 'soft' drink.

25. pH
Material
Gastric juices(stomach)
Lemons
Vinegar
Soft drinks
Sour pickles
Wine
Oranges
Acidic
Tomatoes
Human urine(usually 6.0)
5.6
Carbonated water, rain water
Cow’s milk
Human saliva (during rest)
Human milk
Drinking water

26. pH
Material
Neutral
7.0
Pure water
Human saliva(while eating)
Human blood
Fresh eggs
Seawater
Basic
8.4
Sodium bicarbonate(saturated)
9.4
Calcium carbonate(saturated)
10.5
Milk of magnesia
Household ammonia

27. Le Chatelier’s Principle states that:
when a stress is placed on a system in equilibrium, the system tends to change in a way that relieves the stress.

28. pHun with 'Bad Breath' H2CO3 CO2 + H2O
If CO2 is blown into water, equilibrium shifts left
 [H2CO3] increases  acidity increases
But add citric acid to HCO3- from Alka Seltzer
H2CO HCO H+
bicarbonate
More H+ means more H2CO3 which (According to Le Chatelier’s P.) produces more CO2 which escapes as bubbles( and the customer is happy).

29. Escaping CO2 gives your (leavened)Bread a Lift !

30. pH of Blood( must be kept constant!)
H2CO H2O H3O HCO3-
If pH drops, eg. during illness, the [H3O+] begins to increase but will react with HCO3- to form H2CO3, ie. CO2, which is exhaled. Or the reverse if pH of blood drops.
[H2CO3] is maintained by exhaling / inhaling CO Keep your lungs in good working order!
What happens to blood pH when hyperventilating?

31. LeChatelier’s Principle
H2O + CO2 -> H2CO3
If more CO2 is produced (ie hyperventilation) , then body reacts to produce more H2CO3 to offset the change and the pH drops.

32. Buffers in Blood Keep pH near 7.40
If pH drops below 7.35, called “acidosis”
pH below 7.0 or above 7.8 can cause death
Buffer contains a weak acid (H2CO3) and the salt of a weak acid and a strong base ie NaHCO3.

33. Effects of added acid and base to a buffer
Added base reacts with the weak acid to neutralize it
Added acid reacts with HCO3- to produce H2CO3.

34. Some Common Antacids Name Formula Product
1) Magnesium hydroxide 2) Calcium carbonate ) Sodium carbonate ) Aluminum hydroxide 5) I ) & magnesium carbonate ) Dihydroxyaluminum sodium carbonate )1 + 2
Mg(OH)2 CaCO3 NaHCO3 Al(OH)3
MgCO3
NaAI(OH)2CO3
Milk of magnesia Tums, Di-Gel AlkaSeltzer, soda Amphojel Maalox, Mylanta
Di-Gel liquid
Rolaids " sodium-free
Antacids, for 'heartburn', = ~$1 billion(US)/yr in NA

35. Ah… Relief = Neutralization

36. Build a 'Better' Antacid, and the World….
Instead of CaCO3 let's try a stronger base Mg(OH) HCl MgCl H2O
OOPS, it's a laxative!
Right idea, try again with even more OHs Al(OH) HCl AlCl H2O
DAMN, this time it constipates!
Why not combine them!? But it will never sell as: Magnesium Aluminum Hydroxide

37. How about? MgAlox No, too 'nerdy', but-