Properties of acids and bases

advertisement
Properties of acids and bases








Sour/tart taste
Conduct electricity
Litmus turns red
Release H+ into
water
pH < 7
Neutralize a base
Usually start with H
Most food items








Slippery to the touch
Bitter taste
Conduct electricity
Litmus turns blue
Release OH- into
water
Neutralize an acid
pH > 7
Most cleaning items
An acid is a compound that gives H+ (or
H3O+) in water. Acids generally begin with H.
HCl + H2O  H3O+1 + Cl-1
HCl  H+1 + Cl–1
A base is a compound that gives OH- in
water. Bases usually end in –OH.
NaOH  Na+1 + OH-1
An indicator is a colored substance that can
exist in either an acid or base solution.
Two common indicators:
Litmus paper: red  blue
6.8  7.3
Phenolphthalein: clear  pink
8.3  8.4
Monoprotic: acids or bases that give off one
H+1(acid) or OH-1(base)
HCl  H+1 + Cl-1
NaOH  Na+1 + OH-1
Diprotic: acids or bases that give off two H+1
(acid) or two OH-1(base)
H2SO4  2 H+1 + SO4-2
Ca(OH)2  Ca+2 + 2OH-1
Triprotic: acids or bases that give off three
H+1(acid) or three OH-1(base)
H3PO4  3H+1 + PO4-3
Al(OH)3  Al+3 + 3 OH-1
Ions – charged particles
Naming acids
Common acids normally begin with H. When
you see a compound that begins with H, it
should be named as an acid. The name of the
acid depends on the negative ion:
•If the name of the anion ends in –ide
Hydro (anion without –ide) –ic acid
HCl – hydrochloric acid
HBr – hydrobromic acid
H2S – hydrosulfuric acid
•If the anion ends in –ate, everything is the
same except do not add the prefix hydro(anion name without –ate) –ic acid
HNO3 – nitric acid
HClO3 – chloric acid
H2SO4 – sulfuric acid
Common acids and bases







HCl
HNO3
H2SO4
HC2H3O2
HBr
H2CO3
H3PO4





NaOH
KOH
Ca(OH)2
Mg(OH)2
Ba(OH)2
Bronsted Acid-Bases
Acid – a substance that gives up H+
Conjugate Base – what is left after the acid
gives up H+
Base – a substance that gains H+
Conjugate Acid – what is left after the base
gains H+
Plain acids and bases are on the left side of
a reaction, the conjugate acid and base are
on the right side of a reaction.
C2H3O2-1 + NH4+1  HC2H3O2 + NH3
H2O + H3PO4  H3O+1 + H2PO4-1
H2O + NH3  OH-1 + NH4+1
[ ] = concentration (unit of molarity)
In pure water at 25oC
[H+1] = 1.00 E-7 M
[OH-1] = 1.00 E-7 M
[H+1]x[OH-1] = 1.00E-7 x 1.00E -7 = 1.00E-14
One way of expressing the [H+1] or the
[OH-1] is the pH.
pH = -log[H+1]
pOH = -log[OH-1]
Important Formulas:
pH + pOH = 14.00
[H+1] x [OH-1] = 1.00 E-14
pH = -log[H+1]
pOH = -log[OH-1]
pH Scale
06.99
acid
7.00
neutral
7.01  14.00 base
To calculate the pH (or the pOH)
1.
(-)
2. log
3. [H+1] (or [OH-1]
To calculate [H+1] (or [OH-1])
1.
10x (2nd log)
2. (-)
3. pH (or pOH)
Neutralization Reactions
An acid will react with a base and neutralize
each other. The result when they are mixed
is ALWAYS salt and water.
Acid + Base  Salt + Water
HA + BOH  BA + HOH
HCl + NaOH  NaCl + HOH
To predict the products of neutralization
reactions:
1. Recognize that it is a double replacement
reaction
2.Pair up the new products: one will always
be HOH (or water, H2O)
3.You can get the correct charges from H+1
or OH-1
4.Get the correct formulas by crossing the
charges
5.Balance the reaction
H2SO4 + Al(OH)3 
• H2SO4 + Al(OH)3  HOH + AlSO4
(pair up new products)
• H2SO4 + Al(OH)3  HOH + Al2(SO4)3
(get the correct formulas)
• 3H2SO4 + 2Al(OH)3  6HOH + Al2(SO4)3
(balance the reaction)
Titration – a solution of a known
concentration is reacted with a known
volume of a solution of unknown
concentration. At the endpoint, an indicator
will change colors. At that point,
the [H+1] = [OH-1]. From this information,
the unknown concentration can be
determined.
1. Write a balanced reaction
2. Label all numbers
3. Use unit analysis
4. Start with the volume of the compound
that you know both volume and
concentration
5. vol  moles A  moles B  conc B
27.5 milliliters of H2SO4 is exactly
neutralized by 39.3 milliliters of 0.437 M
NaOH. What is the concentration of the
acid?
H2SO4 + 2 NaOH  Na2SO4 + 2 HOH
Acid: 27.5 ml
Base: 39.3 ml
0.0393 L NaOH
0.437 M
0.437 mol NaOH
1 mol H2SO4
1 L NaOH
2 mol NaOH
1
=
0.0275 L H2SO4
0.312M H2SO4
There is an alternate way to do titration
calculations that does not involve writing
balanced reactions or unit analysis:
PLHABTSM®
M1V1P1 = M2V2P2
M1 = conc of acid
M2 = conc of base
V1 = volume of acid
V2 = volume of base
P1 = protacticity
P2 = protacticity
Protacticity
P1 = # of H+1 per molecules
P2 = # of OH-1 per molecules
1. Read the problem
2. Label all of the numbers
3. Identify the unknown
4. Use M1V1P1 = M2V2P2
5. Solve for the unknown
27.5 milliliters of H2SO4 is exactly
neutralized by 39.3 milliliters of 0.437 M
NaOH. What is the concentration of the
acid?
M1 =
M2 =
V1 =
V2 =
P1 =
P2 =
Download
Related flashcards

Salts

21 cards

Chemical properties

18 cards

Molecular physics

14 cards

Petroleum products

25 cards

Colloidal chemistry

18 cards

Create Flashcards