ACIDS and BASES. Not the stuff you already know!!!

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