acids burn.. bases burn. vi. strength of acids and bases a. strong acids and bases… 1. completely...
TRANSCRIPT
Acids burn.
Bases burn.
VI. Strength of Acids and BasesA. Strong acids and bases…
1. completely dissociate (come apart) or ionizes 100% of the molecules become ions2. are strong electrolytes and dangerous!
Ex. acids: HCl, HBr, HI, HNO3, H2SO4, HClO4
bases: NaOH and other Group 1 or 2 hydroxides
B. Weak acids and bases… 1. dissociate or ionize very little
maybe only 1% of molecules become ions2. are weak electrolytes
Ex: acids: acetic acid, carbonic, and many others bases: ammonia and many others
STRONG ACIDS
STRONG Bases
C. pH Scale1. In any solution, if you pay attention only to the
concentration of hydronium H3O+ (same as H+ !!!)
and hydroxide OH- ions…
…and use brackets [ ] to mean “the concentration of…”
then..
In an acidic solution: [H+] > [OH-]
In a neutral solution: [H+] = [OH-]
In a basic solution: [H+] < [OH-]
Ex. Is the solution shown at right
acidic, basic or neutral?
H+
OH-
H+
H+
OH-
H+
OH- H+
H+
OH-
OH-
OH-
OH-
2. The pH scale is used to express how acidic or basic a solution is.
a/ The pH scale goes from 0 to 14
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
neu
tralstronger acids
more acidicmore [H+] or [H3O+]
stronger basesmore basicmore [OH-]
b/ pH = 7 means a neutral solution with [H+] = [OH-]
Lower pH (< 7): more acidic with [H+] > [OH-]
Higher pH (> 7): more basic with [OH-] > [H+]
Ex. As acid is added to base, what happens to the..
…the pH?
…the acidity? …the basicity?
…the H3O+ concentration? …the OH- concentration?
Ex. Which pH value is most basic?
11 13 2 7 4
Ex. Which pH value it most acidic?
11 13 2 7 4
Ex. Which pH value has the greatest [H3O+]?
11 13 2 7 4
Ex. Which pH value has the greatest [OH-]?
11 13 2 7 4
Sometimes it is written right to left:
Ex. The list at right
gives the pH’s of some
common solutions.
a/ Write A (acid), B (base) and N (neutral) next to each
b/ Put them in order…
…from strongest acid to strongest base:
…of increasing H+ (or H3O+) concentration.
…of increasing OH- concentration.
bleach: 13
blood: 7.4
coffee: 5
OJ: 3
pure water: 7
3/ pH is logarithmic. This means that…
a change …means a change in pH of: in concentration of:
1 101 or 10x
2 102 or 100x
3 103 or 1000x
etc
Ex. Which has a greater [H+] or [H3O+]:
urine (pH 6) or pure water (pH 7)?
How much greater?
Which has a greater [OH-]?
How much greater?
Ex. Which has a greater [H+]: soapy water (pH 12) orbaking soda (pH 9)?
How much greater?Which has a greater [OH-]?How much greater?
Ex. Which has a greater [OH-]: a can of soda (pH 3) or black coffee (pH 5)?
How much greater?
Which has a greater [H30+]?
How much greater?
Ex. The pH of a solution changes from 4 to 3. Did the [H+] decrease or increase? By what factor?Did the [OH-] dec. or incr.? By what factor?