Transcript acids and bases - IDS-chem2-Rn-10

ACIDS AND
BASES
Angela M. Colonia
and
Kristine Marie C. Pa-alisbo
Physical and Chemical behavior
Acids
• corrosive to metals
• change litmus to red
• become less acidic when mixed with bases
• release a hydrogen ion into water (aqueous)
solution
• neutralize bases in a neutralization reaction
Bases
• change litmus to blue
• become less basic when mixed with acids
• release a hydroxide ion into water solution
• neutralize acids in a neutralization reaction
• denature protein
How do we differentiate them?
Acids
• when added to water produces hydrogen
ions [H+]
• tastes sour
Bases
• when added to water produces hydroxide ions
[OH-]
• feels slippery
• tastes bitter
Identifying the strength
Strong acids
• completely dissociate in water, forming H+ and an
anion
•uses only one arrow (→) is required since the reaction
goes virtually to completion
Weak acids
• Incompletely ionized acids because there is a smaller
concentration of ionized hydrogens available in the
solution
• partially dissociates in water to give H+ and the anion
• uses the double arrow because equilibrium exists
between the dissociated ions and the undissociated
molecule
Strong Bases
• dissociate 100% into the cation and OH- (hydroxide ion)
•They are hydroxides of Groups I and II. The hydroxides
of Group II metals produce 2 mol of OH- ions for every
mole of base that dissociates. These hydroxides are not
very soluble, but what amount that does dissolve
completely dissociates into ions.
Weak bases
• due to the presence of an amino group -(NH2) attached
to an organic compound
• They are anions of weak acids.
• They do not furnish OH- ions by dissociation. They
react with water to furnish the OH- ions.
• When reacts with water the OH- comes from the water
and the remaining H+ attaches itself to the weak base,
giving a weak acid as one of the products.
How are they quantified
2 ways:
• pH
- expresses how acidic or alkaline a water solution is
• titration
- rhymes with "tight nation," and refers to a
commonly used method of (usually) finding the
concentration of an unknown liquid by comparing it with
a known liquid
pH Indicators
• in the form of plant pigments known as antocyanines
- which change color over different pH ranges,
depending on source.
Common uses/applications
• manufacture of other chemicals
- Fertilizers, synthetic fabrics, pigments,
petroleum, iron and steel, explosives, dyes, plastics,
pesticides, soaps and detergents, paper, film, and many
other chemicals
• various other purposes
- cleaning surfaces, refining oil and sugar,
electroplating metals, and treating food products