1. Acids and Bases (P )
Lesson 12
September 14th, 2010

2. Acids and Bases (P )
Acids are traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion activity greater than in pure water, i.e. a pH less than 7.0.

3. When Acids are dissolved in water they release H+ .
Ex HCl(aq)  H+(aq) + Cl-(aq)

4. They also:
Taste sour
Are good conductors of electricity (they release H+ ions when they are in water)
React with compounds that contain carbonate
Are generally quite reactive
Inflict a sharp burning pain when handled
Turn blue litmus red

5. Identifying Acids
You can identify an acid from its name or from its chemical formula. Usually, the name of an acid ends with the word “acid.” If you are given the chemical formula of a substance, you know that it is an acid if:
the chemical formula starts with H (the symbol for a hydrogen atom) OR
the chemical formula ends with COOH (the formula for a carboxyl polyatomic ion)
Example – HF(aq)­ hydrofluoric acid, CH3COOH­ (aq) acetic acid.

6. Naming Acids
There are two rules for naming acids when the chemical formula of an acid starts with H and has only one other non-metallic element
Step
Examples
HCl (aq)
HF (aq)
Start with the Prefix “hydro”
hydro
Hydro
2.To the first part of the name of the non-metallic element, add the suffix “ic” and add the word “acid”
Hydrochloric acid
Hydrofluoric acid

7. Naming Acids (with polyatomic ions)
Some acids contain a polyatomic ion. When the polyatomic ion in an acid contains an oxygen atom (O) and its name ends in “ate”, the acid can be named by the steps shown below.
Step
Examples
H2SO4(aq)
H3PO4(aq)
Start with the name of the element in the polyatomic ion that is not oxygen
sulphur
phosphorus
2.Add the suffix “ic” and the word “acid”
sulphuric acid
phosphorusic acid

8. Sour milk or tired muscles
Table 1 Examples of common acids include
Common acids
Common name
Formula
Source or use
Vinegar (acetic acid)
HC2H3O2 or HC2H2OOH
Salad dressing
Citric acid
HC6H7O7
Oranges, lemons
Ascorbic acid
HC6H7O6
Vitamin C
Lactic acid
HC­3H5O3
Sour milk or tired muscles
Sulfuric acid
H2SO4
Car batteries

9. Acids are widely used in industry, they are used in many manufacturing processes including; fertilizers, explosives, refining oil, and electroplating materials.
Acids that that react with metals and glass are described as being Corrosive. These acids can be dangerous to humans and the environment.

10. Base
 A base is most commonly thought of as an aqueous substance that can accept hydrogen ions.
bases can commonly be thought of as any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion activity lower than that of pure water, i.e. a pH higher than 7.0 at standard conditions.

11. When bases are released in water they release OH- ions
Example
NaOH (aq)­  Na+ (aq) + OH- (aq)

12. They also: Taste bitter
Are good conductors of electricity (They release OH- ions when dissolved in water)
Break down proteins into smaller molecules
May also be called alkaline
Feel slippery when handled
Turn Red litmus blue

13. Identifying and Naming Bases
A base can also be identified from its name or its chemical formula. A substance is a base if its name begins with the name of a metallic ion and ends with the word “hydroxide.” A substance is also a base if:
the chemical formula starts with a metallic ion or with the ammonium ion NH4+
AND
the chemical formula ends with OH (called a hydroxyl group)

14. Naming Bases
The name of a base can be determined from its chemical formula by following the steps shown in Table 5.5. Notice that all bases (in this class) are followed by the word “hydroxide.”

15. Naming Bases Step Examples KOH (aq) NH4OH (aq)
Write the name of the positively charged metallic ion that is at the beginning of the chemical formula. This step remains the same if the positively charged ion is a polyatomic ion.
Potassium
Ammonium
Add the word “hydroxide”
Potassium hydroxide
Ammonium hydroxide

16. Table 2 Examples of some common bases
Common Name
Formula
Source or use
Sodium hydroxide
NaOH
Drain cleaner
Potassium hydroxide
KOH
Soap, cosmetics
Aluminum hydroxide
Al(OH)­3
Antacids
Ammonium hydroxide
NH­­4OH
Window cleaner.
Sodium bicarbonate
NaHCO3
Baking soda, used in baking
Potassium sulphite
K2SO3
Food preservative

17. Bases that feel slippery to the touch are Corrosive and should be handled carefully with gloves and eye protection.

18. Where do Acids and Bases come from?
Acids and bases do not exist in nature as raw materials
Raw materials – materials from the earth that can be used to make new products
Acids and bases are formed when certain elements react with oxygen to form oxides.

19. Reactions of Metals
Metals tend to lose electrons and react with oxygen to form solid metal oxides. When these oxides are mixed with water they react and form bases, many of these bases are very strong when concentrated.
Example
2Mg + O2  2MgO
MgO + H2O  Mg(OH)2

20. Reactions of Nonmetals
Generally elements from the groups VA, VIA, and VIIA need electrons to complete their valence and are called nonmetals. Nonmetals react with oxygen to form nonmetal oxides which are normally gases. These oxides then form acids when mixed with water.
Example
S8 + 8O2 8SO2
SO2 + H2O  H2SO3

21. Homework /msip
Read pages 293 – 295 # 2,3,4,6