Introduction to Acids And Bases
The chemical formula of pure water, as you know is H2O. Pure water may dissociate into equivalent amonts of
H+1
ions and OH-1ions. Hence, water is considered to be neutal. These two ions the H+1
and the OH-1 ion are what causes solutions to be either acid or basic.
When a solution has more H+1 ions in solution than OH-1 ion., the solution is considered to be acidic.
When a solution has more OH-1ions in solution than H+1 ions, the solution is considered to be basic or
alkaline.
These two concepts are the basis of the Arrhenius theory of acids and bases.
Acids
Vinegar, orange juice Pepsi, & battery fluids are all examples of acids. What are the properties of acids?
- Acids tend to be clear colourless liquids or solutions, that may give of a vapour.
- They taste sour.
- They react with certain metals to produce hydrogen gas.
- They will neutralize bases to produce water and a salt. This type of reaction is called neutralization.
- Acids will react with indicators to change thier colour.
When an acid dissociates or dissoves in water H+1 are released
HA -----------> H+1 + A-1
as shown in this picture
Bases
Common bases are baking soda, antacids, borax, some cleansing agents. What are the properties of bases?
- Bases taste bitter
- Bases feel slippery to the touch
- Bases react with acids to produce water and a salt, neutralizing them.
- Bases react with indicators to produce a specific colour
A base dissociates in water to produce the hydroxide (OH-1) ion.
MOH ----------> M+ + (OH)-1
where M represents any metal ion
Her's a small list of some acids and bases and where they may be found and/or use
| Common Name |
Formula and name |
Use &/or Product |
| Battery acid |
H2SO4
sulfuric acid |
Car batteries |
| Citric acid |
C6H8O7 |
Orange and other fruit juices |
| Vinegar |
CH3COOH
acetic acid |
Salad dressings |
| Muriatic acid |
HCl
hydrochloric acid |
Cement cleaner and neutralizer |
| Phosphoric acid |
H3PO4 |
Coke and Pepsi. |
| Antacid |
Mg(OH)2 & Al(OH)3
Magnesium & aluminum hydroxides |
Maalox |
| Oven cleaner |
NaOH in foam
sodium hydroxide |
Easy-Off |
| Ammonia cleaner |
NH3 in solution |
Amex cleaner |
| Drain cleaners & openers |
NaOH & KOH
sodium& potassium hydroxides |
Drano, Liuquid Plumber |
| Baking Soda |
NaHCO3
sodium bicarbonte |
for cooking and neutralizing acids |
The pH Scale
Definition: the pH of a solution is the negative logarithim of the
hydrogen ion concentration. The hydrogen ion concentration is measured in moles per litre .
The formula is pH = - log[H+1 ] . See page 297 .
Converting pH values to concentration values and back again will be dealt with in class. Its a "calculator thing".
The pH scale is a range of values from 0 to 14, with 0 being the most acidic and 14 being the most basic.
A pH of 7 is considered neutral (the pH of pure water is 7). Acids have low pH while bases have large pHs. a chart of
pH's can be seen below or on page 296 of your text book.
Indicators
Indicators are chemicals that have a certain colour based on the pH of the solution that they are in. Hence if the pH is allowed to change the colour of the indicator will also change.
The five indicators that you may see are as follows
- litmus paper, red and blue
- phenolphthalein
- bromthymol blue
- methyl orange
- methyl red
Here's a diagram indicating their colour ranges at ph's ranging from 0 to 14. Make sure you read the chart carefully so that you don't mix up the indicators.
More are shown here than the five listed above.
Note: the white you see in the chart does not mean white it means colourless
Formation of acids and bases
from metallic and nonmetallic oxides click here 
From the "R-Files"
And a wrap-up note from Miss Rossini
