Acids and Bases
Acids and bases make up some of the most familiar chemicals in our lives, they're some of the most important chemicals in labs and industries.
The ion common to all acids is the hydrogen ion, H+. An acid is a commpound that donates H+ ions (protons) in aqueous solution. The process is called dissocating.
Common acids and formulae:
- Hydrochloric Acid - HCl
- Sulfuric Acid - H2SO4
- Nitric Acid - HNO3
- Etanoic Acid - CH3COOH
The equation for hydrochloric acid dissociating is given by:
HCl(g) >water> H+(aq) + Cl-(aq)
A base is a compound that accepts H+ ions from an acid.
Common bases and formulae:
- Magnesium oxide MgO
- Sodium hydroxide NaOH
- Calcium oxide CaO
- Ammonia NH3
If the base dissolves in water it's called an alkali. The ion common to all alkalis is the hydroxide ion, OH-.
Strong and weak acids
- A strong acid is one that fully dissociated in aqueous solution
- A weak acid is one that partially dissociates in aqueous solution
The more easily an acid can donate H+ the stronger the acid. A strong acid is fully dissociated in aqueous solution. Many acids are far from fully dissociated in aqueous solution and these are describes as weak acids. A concentrated acid consists of a large quantity of acid and a small quantity of water. A dilute acid contains a large quantity of water.
The pH scale
Since acids are compounds that donate H+ ions, the acidic of a solution is a measure of the concentration of the aqueous hydrogen ion, H+.
The problem with the pH scale was overcome in 1909 when Soren Sorenson proposed the pH scale:
pH = -log[H+] (H+ is the concentration of H+ in moldm-3)
The negative sign in the equation results in pH decreasing as the…