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ACIDS and BASES.
Not the stuff you already know!!!
Ways to define acids- Arrhenius
• Arrhenius is one way to characterize acids and bases- it has to do with what they do in water.– Arrhenius Acid (AA)- is one that produces
H+ in water.– Arrhenius Base (AB) is one that produces
OH- in water– Limiting because only water solutions and
only one type of base, an OH
Some examples
• HCl + H2O H3O + + Cl -
• HNO3 + H2O H3O + + NO3-
Bronsted Lowery acids
• A more general way to describe acids and bases• An acid is anything that can donate a H+ ( a proton
donor)• A base is anything that accepts a H+ ( a proton acceptor)
• That means acid and bases always occur in pairs, you always have one acid and one base as reactants, and one acid/one base on products
• A H+ is also called a hydronium ion. When added to water write H3O+
Conjugate acids and bases
• A conjugate is anything on the product side that remains after a proton has moved.
• HCl + H20 H3O + + Cl-
Acid base conjugate acid conjugate base
Keep in mind both bases can compete for the proton, will need to determine which is stronger to establish equilibrium
How to write them
• HCl + H2O
• HNO3 + H2O
• H2SO 4 + H2O • Try pg 625
There is an equilibrium expression for this!
• Ka = products over reactants, • Called an acid dissociation constant• Tells you how well the acid comes apart.• Ka< 1, mostly reactant ( doesn’t dissociate
well) WEAK ACID• Ka >1 comes apart well, mostly product
STRONG ACID• Ka = 1, even mix of the 2 in solution
Strong and weak, concentrated and dilute
• Strong and weak have to do with how reactive they are
• Chart gives some idea• Bases, OH is strong
• Nice to know (not have to look up)
• HCl, NH3,H2SO4, H3PO4, OH
• Concentrated and dilute have to do with how much substance per how much water.
• This is molarity/ molality.
• High molarity is concentrated
Other types of acids
• many acids are diprotic or triprotic- have 2 or 3 H. The first H to come off is usually strong, but the rest are usually weak
• Oxyacids are H attached to a polyatomic ion• Organic acids are carbon chains, usually weak
acids • For very strong acids, Ka is not accurate because
the equilib. Is so far to right, and therefore not very useful
How to get rid of more than one Hydrogen
• If an acid has only one H+ to give away, it is called monoprotic acid– ( a Hydrogen without it’s electron is just a
proton)• Examples include HCl, HF, HNO3
• If an acid has 2 Hydrogens to give away, Diprotic, or 3, triprotic– Examples include H2S, H2SO4 H3PO4
Base dissociation
• Ca(OH)2 becomes Ca + 2OH-• Na(OH) becomes Na + OH-• NH3 +H2O NH4
+ + OH-• CH3COO- + H2O becomes CH3COOH +
OH-
• Strong bases have OH, weak have to compete w/ water to get it, so weak
Ka and Kb• Keeping in mind that Ka = products over reactants, and
large ka= strong acids,
• Kb is the strength of the base, is also products over the reactants, and high Kb= strong bases.
• A strong acid will have a weak conj. Base, and• a weak acid will have a strong conjugate base
• So the stronger the acid, the weaker its base, and if you are a really strong acid ( HCl, H2SO4) don’t’ even have Ka’s for it.
Water as acid and base• Water is amphoteric, it can act as acid or base. It
also tends to come apart on it’s own. • Autoionization is the term for water separating
into acid and base• The Kw for water describes the number for this.• H2O H+ + OH-
• at 25 ° the [H+ ] = 1. x10 -7 and• [ OH-] = 1 x 10 -7, • so the Kw= [H+ ][ OH-]• So Kw = 1 x 10 -14
pH
• This auto ionization is the whole idea behind pH• Kw is always 1 x 10-14 at 25°, but the ratio of H
and OH change with acids and base.
• Literally pH stands for the power of the Hydrogen, and pOH stands for the power of the OH.
• If H > OH, acid, if H<OH base, if H=OH neutral.
pH continued
• Ok, so pH = -log [H+]
• If [H+] = 1 x 10-3, pH =3 acid
• If [H+] = 1 x 10-5, pH =5 acid
• If [H+] = 1 x 10-9, pH =9 base
• If [H+] = 1 x 10-14, pH =14 base
• See a pattern?
pH continued
• Ok, so pH = -log [H+]• What if it isn’t quite that easy? Since pH is the power of
the H, even if it isn’t a “1” the pH will be close to the exponant, but you will need to know how to use your caluclator!!!
• If [H+] = 2 x 10-3, pH =2.66 acid• If [H+] = 3.55 x 10-5, pH =4.45 acid• If [H+] = 9.8 x 10-9, pH =8.009 base• If [H+] = 6.99 x 10-14, pH =13.15 base
• You try them?
H and OH, pH and pOH
• H and OH are 2 parts of a whole, the whole being 1.0 x10-
14, • Remember that Kw = [H+ ] [OH-] • and Kw = 1 x 10-14
• So…
• so if [H+ ]= 1 x 10-5, [OH-] = 1 x 10 -9
• so if [H+ ]= 1 x 10-3, [OH-] = 1 x 10 -11
• so if [H+ ]= 1 x 10-10, [OH-] = 1 x 10 -4
• so if [H+ ]= 1 x 10-2, [OH-] = 1 x 10 -12
• so if [H+ ]= 2.1 x 10-3, [OH-] = 4.76 x 10 -12
• You try them too!
Neutralization
• Strong Acids and strong bases make water and salt
• Not always NaCl salt. Just an ionic compound.
• 2HF + Mg(OH)2 2H2O +MgF2
• 2H+ + 2F- + Mg+2 + 2OH- 2H2O +MgF2
Types of salts
• A strong acid and weak base = slightly acidic salt
• Strong base and weak acid= basic salt
• Weak acid and base, varies
• When compounds have high oxidizing metals, always slightly acidic ( Al+3, Fe+3)
How concentration affects strength
• So far worked pH from {H3O}concent.• What if given from chemical?
• .001 M HF?– HF H+ + F- , so HF & H+ are same, .001– But what if .001 H2SO4?– H2SO4 2H+ + SO4
-2 , – so H+ is double, .002
Oxides, some acids, some bases
• Metal oxides tend to make bases• CaO, + H2O Ca(OH)2, K2O + H2O KOH
• NONmetal oxides tend to make acids
• SO3 + H20 H2SO3 CO2 +H20 H2CO
Lewis acids/bases
• Even more broad in definition• Electron pair donor, acceptor• If has a unshared pair of electrons, is the Lewis
base• Accepting the electrons, Lewis acid• ( opposite of BL in theory)• NH3, H2O, tend to have the e- pair, are bases• H+, Ni+2, Al +3, acceptors, acid
Properties of acid and bases
• Acids• Taste sour• Turn pH paper red• pH of 0-6• Acids feel like water• Can be caustic• Foods like fruits, vinegar,
soda, yogurt• Conduct electricity• React with metals
• Bases• Tastes bitter
• Turn pH paper blue
• pH of 8-14
• Feel slippery
• Can be caustic
• Ammonia, soap, pickles
• Conduct electricity
• Do not react with metals
•Acids + bases = water +salt
Common names for acid and base
• Acids• Muratic acid- stomach
acids and cleaner• Oranges, limes, lemon all
have citric acid• Soda, sour candy-
phosphoric acid• Walnuts- tannic acid• Apples – malaic acids• Vinegar- acetic acid• Vitamin C- ascorbic acid
• Bases
• Ca(OH)2 - tums
• NH3 Ammonia
• Lime CaCO3
• Lye NaOH
Industrial acids• Muratic acid- HCl, cleaner of pools and
concrete, also of steel, food processing, recovering Mg from sea water, and other food creation processes. Stomach acid
• Sulfuric acid- most common industrial acid, fertilizer production, car batteries, refining process for many plastics, metals, paint, paper, dyes etc. Great for dehydration process ( sugar refining)
More industrial acids• Nitric acid- Not stable, so less commonly used, used in
production of rubber and plasitcs, pharmacuitcals and explosives.
• Phosphoric acid- beverages and candy, to clean food equipment. also in fertilizers ( DNA is P based) detergents and ceramics
• Acetic acid- glacial is very concentrated, vinegar. Synthesizing chemicals used in plastic production, many foods, production of essential amino acids. Also a fungicide.
1. 12 M HCl is __________2. (choose) strong/ weak and it is concentrated/dilute
3. .2 M H2SO4 is 4. (choose) strong/ weak and it is concentrated/dilute5. 1 M NaOH is ____________6. (choose) strong/ weak and it is concentrated/dilute
7. 12 M NH3 is _____________8. (choose) strong/ weak and it is concentrated/dilute
9. .5 M H3PO4 is ___________________10. (choose) strong/ weak and it is concentrated/dilute
11. 15 M H3P is 12. (choose) strong/ weak and it is concentrated/dilute