i. intro to acids & bases€¦ · acids bases react with metals to form h 2 gas vinegar, milk,...
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Acids Bases
react with metals
to form H2 gas
vinegar, milk,
soda, apples,
citrus fruits
bitter taste
turn litmus blue
substance that changes color in an acid or base
Examples: litmus - red/blue phenolphthalein - colorless/pink goldenrod - yellow/red red cabbage juice - pink/green
•Acids contain hydrogen ions
•Bases contain hydroxide ions (OH-)
Savante Arrhenius, Swedish
chemist who by 1890
formulated the first useful
theory for acids.
•Acids are proton (H+) donors.
•Bases are proton (H+) acceptors.
• Conjugate acid-base pairs are formed.
HCl + H2O Cl
– + H
3O
+
conjugate acid conjugate base
base acid
Pairs identifies the particles formed when H+ ions
are donated and accepted when an acid or a base is
dissolved in water.
Base gains H+ conjugate acid formed
Particle that remains conjugate base
HCN(aq) + SO4−2
(aq) → HSO4−
(aq) + CN−(aq)
H2O(l) + NH3(aq) → NH4+
(aq) + OH−(aq)
HCO3−
(aq) + H2O(l) → H3O+(aq) + CO3
−2(aq)
HCO3−
(aq) + H2O(l) → H2CO3(aq) + OH−(aq)
Dissociation: ionic compounds dissolve to produce ions
Ionization: molecular compounds dissolve in water to produce ions
The level of dissociation/ionization determines the strength of acid/base.
Strong Acid/Base 100% ionized in water many ions produced strong electrolyte
- +
HCl
HNO3
H2SO4
HBr
HI
HClO4
NaOH
KOH
Ca(OH)2
Ba(OH)2
Weak Acid/Base
• does not ionize completely
• few ions produced
• weak electrolyte
- +
HF
CH3COOH
H3PO4
H2CO3
HCN
NH3
Acids & Bases
Basis for pH scale that is used to quantitatively examine the H+ ion concentration of solutions.
Kw= [H+][OH-]
Kw = (1.0 x 10-7M) x (1.0 x 10-7)
Kw =1.0 x 10-14
pH scale is derived from the value of Kw
pH of Common Substances
0
7
NEUTRAL INCREASING
BASICITY
14
INCREASING
ACIDITY
pH = -log[H3O+]
pOH = -log[OH-]
pH + pOH = 14
What is the pH of 0.050 M HNO3?
pH = -log[H3O+]
pH = -log[0.050]
pH = 1.3
Acidic or basic? Acidic
Acids & Bases
Analytical method in which a standard solution is used to determine the concentration of an unknown solution.
standard solution
unknown solution
Equivalence point (endpoint)
Point at which equal amounts of H3O+ and OH- have been added.
Determined by…
indicator color change
• dramatic change in pH
moles H3O+ = moles OH-
MV n = MV n
M: Molarity
V: volume
n: # of H+ ions in the acid or OH- ions in the base
42.5 mL of 1.3M KOH are required to neutralize 50.0 mL of H2SO4. Find the molarity of H2SO4.
H3O+
M = ?
V = 50.0 mL
n = 2
OH-
M = 1.3M
V = 42.5 mL
n = 1
MV# = MV#
M(50.0mL)(2)
=(1.3M)(42.5mL)(1)
M = 0.55M H2SO4
Chemical reaction between an acid and a base.
Products are a salt (ionic compound) and water.
ACID + BASE SALT + WATER
HCl + NaOH NaCl + H2O
• Salts can be neutral, acidic, or basic.
• Neutralization does not mean pH = 7.
Double replacement reaction where a precipitate is formed due to the insolubility of the compound that is formed.
Refer to the solubility rules.
A chemical reaction in which one reactant loses electrons and another gains electrons.
The reactant being oxidized (losing electrons) is said to be the reducing agent.
The reactant that is reduced (gaining electrons) is said to be the oxidizing agent.
2Fe + O2 2FeO
All batteries produce electricity by means of redox reactions.