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Intro to Acids and Bases. (again!). Naming acids . An acid is loosely defined as a compound that produces hydrogen ions (H + ) when dissolved in water Acids are named depending on the anion in the compound. Add H +. Add H +. Add H +. _______ ide (chloride, Cl - ). - PowerPoint PPT Presentation
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Intro to Acids and Bases(again!)
Anion(example)
Acid(example)
_______ ide (chloride, Cl-)
________ate (chlorate, ClO3
-) _________ite (chlorite, ClO2
-)
hydro____ic acid (hydrochloric acid, HCl)
_______ic acid (chloric acid, HClO3)
_______ous acid (chlorous acid, HClO2)
Add H+ Add H+Add H+
Naming acids • An acid is loosely defined as a compound
that produces hydrogen ions (H+) when dissolved in water
• Acids are named depending on the anion in the compound
Acid Anion root NameH2SO4 Sulfate Sulfuric acidH3PO4 Phosphate Phosphoric acidHCl Chloride Hydrochloric acidHC2H3O2 Acetate Acetic acidHNO3 Nitrate Nitric acidHClO2 Chlorite Chlorous acidHClO Hypochlorite Hypochlorous
acid
Writing Formulas AcidsAcid Name Formula Anion Name
Acetic acid HC2H3O2 acetate
Carbonic acid H2CO3 carbonate
Hydrochloric acid HCl Chloride
Nitric acid HNO3 Nitrate
Phosphoric acid H3PO4 Phosphate
Sulfuric acid H2SO4 Sulfate
Names and formulas for Bases A base is a compound that produces
hydroxide ions (OH-) when dissolved in water
Bases are named in the same way as other ionic compounds—the name of the cation is followed by the name of the anion
Examples - Sodium hydroxide (NaOH); potassium hydroxide (KOH)
Strengths of Acids and Bases The strength of an acid/base depends on
how well the ions dissociate Influenced by
Polarity (more polar = stronger) Bond strength (Stronger bonds = weaker
acid/bases because they don’t dissociate) Stability of anion (more stable = stronger)
Strong ≠ high concentration Strength measures the degree of
separation Concentration refers to how many particles
are present
Strength of Acids/Bases Strong acids/bases – completely
dissociate, strong electrolytes Examples you should know: HNO3, H2SO4,
HCl, HBr, HI; KOH, NaOH Weak acids/bases – don’t completely
dissociate and are weak electrolytes Generally, organic acids like acetic acid
(vinegar) Not many weak bases; i.e. NH3
Defining Acids and Bases Multiple ways to define acids and bases Arrhenius acids/bases
Acids are hydrogen-containing compounds that yield hydrogen ions (H+) in aqueous solution
Bases yield hydroxide ions (OH-) in aqueous solution
Arrhenius AcidsH+ is also known as a protonAcids can be monoprotic, diprotic, or
triprotic Monoprotic: HNO3 → H+ + NO3
-
Ionization yields one hydrogen ion Diprotic: H2SO4 → 2H+ + SO4
2-
Complete ionization yields 2 hydrogen ions Triprotic: H3PO4 → 3H+ + PO4
3-
Complete ionization yields 3 hydrogen ions
Arrhenius AcidsNot all the hydrogens in an acid may be
released as hydrogen ionsNot all hydrogen-containing compounds
are acids Only hydrogens joined to very electronegative
elements with very polar bonds, are ionizable in water
H
H
H
H+C C O-
O
Ethanoic Acid
Nonionizable HydrogenIonizable Hydrogen
Arrhenius BasesBases formed with group one metals
are very soluble and caustic NaOH → Na+(aq) + OH-(aq) KOH → K+(aq) + OH-(aq)
Bases of group 2 metals are very weak Examples are Ca(OH)2 and Mg(OH)2
Bronsted-Lowry Acids and Bases Arrhenius definition is not very comprehensive
Ammonia (NH3) is a base, but there is no hydroxide (OH-) in the compound to ionize
The Bronsted-Lowry theory defines an acid as a hydrogen-ion donor, and a base as a hydrogen-ion acceptor
NH3(aq) + H2O(l) → NH4+(aq) + OH-(aq)
Hydrogen ion aceptor,
Bronsted-Lowry Base
Hydrogen ion donor,
Bronsted-Lowry Acid
Makes the solution basic
Conjugate Acids and Bases
A conjugate acid is the particle formed when a base gains a hydrogen ion
A conjugate base is the particle that remains when an acid has donated a hydrogen ion
A conjugate acid-base pair consists of two substances related by the loss or gain of a single hydrogen ion Acids have conjugate bases while bases have conjugate
acids
NH3(aq) + H2O(l) NH4+(aq) + OH-(aq)
Base Acid Conjugate Acid
Conjugate Base
conjugate acid-base pair
conjugate acid-base pair
HCl(aq) + H2O(l) H3O+(aq) + Cl-(aq)Acid Base Conjugate
AcidConjugate
Base
conjugate acid-base pair
conjugate acid-base pair
A water molecule that gains a hydrogen ion becomes a positively charged hydronium ion H3O+
Water can both accept AND donate a hydrogen ion A substance that can act as both an acid and a
base is said to be amphoteric Amino Acids as an example – building block of protein
Lewis Acids and Bases Acids accept a pair of electrons during a reaction
while a base donates a pair of electrons Lewis acid – a substance that can accept a pair of
electrons to form a covalent bond Lewis base – a substance that can donate a pair of
electrons to form a covalent bond MUCH broader, more inclusive definition than any of
the othersNH3 + BF3 → NH3BF3
Identify the Lewis Acid and the Lewis Base in the above equation
H+ + H2O → H3O+
H+
Acid Base
Acid-Base Definitions ReviewType Acid Base
Arrhenius H+ producer OH- producer
Bronsted-Lowry H+ donor H+ acceptor
Lewis electron-pair acceptor electron-pair donor
Reactions of Acids/Bases (Arrhenius and B.L kinds) Single replacement Double replacement
Single Replacement Reactions
A + BC = AB + C A chemical change in which one element
replaces a second element in a compound Acids react strongly with most metals – reactivity
with metals used to be a common way to classify acids
Hydrogen from the acid is always the cation replaced by the metal
Examples:2K(s) + 2H2O(l) 2KOH(aq) + H2(g)2Al (s) + 6HNO3 (aq) 2Al(NO3)3 (aq) + 3H2(g)
Activity Series of Metals Notice that aluminum is higher on
the activity series of metals than hydrogen
A reactive metal will replace any metal listed below it in the activity series
2Al (s) + 6HNO3 (aq) 2Al(NO3)3 (aq) + 3H2(g)
Cu + HNO3 No reaction
Dec
reas
ing
reac
tivity
Single Replacement Reactions
2K(s) + 2H2O(l) 2KOH(aq) + H2(g)
2Al (s) + 6HNO3 (aq) 2Al(NO3)3 (aq) + 3H2(g)
Ca (s) + H2SO4 (aq) CaSO4 + H2(g)
Pt (s) + HCl (aq) N.R.2Na (s) + H2SO4 (aq) Na2SO4 + H2(g)
Practice Problems
Double Replacement ReactionsAB + CD = AC + BDThe ions of two compounds exchange
places in an aqueous solution to form two new compounds Often produce a precipitate, a gas, or molecular
compound such as water
Precipitation (forms a solid or gas as a product) Acid/Base (forms water as product); also known
as a neutralization reaction
Ca(OH)2(aq) + 2HCl(aq) CaCl2(aq) + 2H2O(l)
Reactions in Aqueous SolutionAcid-Base reactions Acids and bases react to form water and a
salt, a generic name for an ionic compoundOH NaCl(aq) HCl(aq) NaOH(aq) 2
OH (aq)Cl (aq)Na (aq)Cl (aq)H (aq)OH (aq)Na 2
H3PO4 + 3Fe(OH)2 Fe3(PO4)2 + 6H2O
H2SO4 + Ca(OH) 2 CaSO4 + 2H2O
OH (aq)H (aq)OH 2