ACIDS AND BASES Chapter 13-14

• If one has an ionic compound and puts it into water, the compound will break into two ions. If one of those ions is H+, the solution is acidic. If one of the ions is OH- the solution is basic.

Ions determine whether the substance is an

acid or base

AcidsAcids

• Acids are compounds that react Acids are compounds that react with bases to form water and a saltwith bases to form water and a salt

• Acids have many distinctive Acids have many distinctive properties:properties:

• Acidic compounds give foods a Acidic compounds give foods a sour or tart tastesour or tart taste

• Aqueous solutions of acids are Aqueous solutions of acids are electrolyteselectrolytes

• Acids cause chemical dyes, called Acids cause chemical dyes, called acid-base indicators to change acid-base indicators to change colorcolor

• Bases are compounds that react with acids to form water and a salt

• Bases have many distinctive properties:

• Aqueous solutions have a slippery feel and a bitter taste

• Bases can be strong or weak electrolytes and bases will change the color of acid-base indicators

• Antacids use a variety of bases to neutralize excess stomach acid

Acids-

They form H+ ions in aqueous solutions

HCl (water)

H+ & Cl-

Bases-

They yield OH- ions in aqueous solutions

NaOH (water)

OH- & Na+

The oldest of the acid- base theories

Acids-

-Hydrogen-ion donor

-They are positive and to balance out, they can give H+ ions

Bases-

-Hydrogen-ion acceptor

-OH- or another ion accepts the positive ions to neutralize

The most common acid-base theory used today

Acids-

-Accepts a pair of electrons to

form a covalent bond

-(They can accept negative

electrons to help neutralize the

atom)

Bases-

-A substance that can donate a

pair of electrons to form a

covalent bond.

-(This atom is negative

already, therefore it can give

off negative electrons to help

balance the atom)

The acid-base theory used by organic chemists

Arrhenius Acids + Bases

• Acid + Base Salt + Water

• HCl + NaOH NaCl + HOH

• HCl + Ca(OH)2

Predict the two products.

Bronsted-Lowry Acids + Bases

• acid + base → conjugate acid + conjugate base

• HCl + NaOH → H2O + NaCl

• In this case, water is the conjugate acid (potential H+ i.e. proton donor).

• In this case, NaCl is the conjugate base (potential H+ acceptor).

• HNO3 + Ca(OH)

2 →

Predict the two products.

Binary Acids--2 elements

-the prefix is “hydro”

ends in “ic”

-HClHydrochloric Acid

-HBrHydrobromic Acid

-HI

-HF

Name these!

Ternary Acids--3 elements or more

-the higher number of oxygens of the polyatomic ion, it ends in “ic” Ex. sulfate

-the lower number of oxygens ends in “ous” Ex. sulfite

-no “hydro” prefix

-name based on polyatomic ion

-H2CO3carbonic

-H3PO4

-HNO3 Name these!

Bases- are named in the same way

as all other ionic compounds

• The acidity of a water sample is measured on a pH scale. This scale ranges from 0(Maximum acidity) to 14(Maximum alkalinity). The middle of the scale represents the neutral point. The acidity increases from neutral toward 0.

pH= -log[H+] When [H+]= 1x10-7, the pH is 7 neutral

Acidic Solution== pH<7.0 [H+] is greater than 1x10-7 mol/L

Basic Solution==pH>7.0 [H+] is less than 1x10-7 mol/L

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pH = -log [H+] Therefore:

pH 7 = -log 10-7M H+ ions

pH 6 = -log 10-6M H+ ions

pH 5 = -log 10-5M H+ ions

NOTE: A change from one pH unit to another is a tenfoldchange in concentration. pH 5 is ten times more acidic than pH 6 and one hundred times more acidic than pH 7.

The mathematics of pH

pOH = -log [OH-] Therefore:

pOH 1 = -log 10-1M OH- ions

pOH 2= -log 10-2M OH- ions

pOH 3 = -log 10-3M OH- ions

NOTE: A change from one pOH unit to another is a tenfoldchange in concentration. pOH 1 is ten times more basic than pOH 2 and one hundred times more basic than pOH 3.

The mathematics of pOH

Reciprocal Relationships

pH = -log [H+][H+] = antilog -pH or 10(-pH)

NOTE: On most calculators, antilog is the 2nd function log button.

This same mathematical setup work for pOH too!

pH + pOH = 14

pKa + pK

b = 14

What about weak acids and bases?

• There are only six strong acids and six strong bases (see p. 376 in Masterson and Hurley)

• All other acids and bases are considered weak, and DO NOT completely disssociate in water.

• In order to find the pH or pOH of a weak acid or base the equilibrium equation must be used.

• It is called the Ka for

acids and the Kb for

bases• K

a X K

b = 1X 10-14

Using the Equilibrium Equation

• Ka or K

b = [products]

[reactants]• For purposes of use in this class you can change the equation as

follows: K

a or K

b = x2

• original solution M • Example: 0.1 M HF xM H1++ xM F1- • 6.9 x 10-4 = x2

0.1 M

• The x can be used to find the pH since it is the dissociated hydrogen ion concentration [H1+] of the weak acid, or the pH can be used as the value for x.

• Using this equation for polyatomic acids is more complex.

pH and Environmental Effects

•

                                                                                                    

                                          

SOx + H2O--> H2SO4--Sulfuric

H2SO3--Sulfurous

NOx + H2O--> HNO3--Nitric HNO2--Nitrous

--The Sulfur found from emissions is naturally found in fossil fuels, in oil and coal. (gasoline)

--Burned to make: electricity

--The Nitrogen and Oxygen are both found in air. They combine during high combustion processes.

Acid Rain Websites• Basic Info

• Graphs and facts

• Soil type

Heartburn-

-Occurs in the Esophagus which has no mucus lining

-Acid from the stomach backs into the Esophagus

-Acid Reflux is a chronic acid iritation of the esophagus due to a weakness of the cardio-oesophageal sphincter

Ulcer-

-Occurs in the stomach which has a thick mucus lining

-The gastric juices have a pH of 1-2

-if there is a “hole” in the stomach acid hits nerve cells and forms an ulcer

H.pylori bacterial infections can destroy the stomach lining allowing ulcers to form

Digestive System Diagram

•

     

                                                                                  

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Heartburn

Heartburn is a pain behind the breast bone, often described as ‘burning’ in quality. Pain can also be felt at the same level in the mid-line of the back. Most people suffer from heartburn at one time or another. In fact heartburn has nothing to do with the heart - it is a digestive problem. Heartburn is generally related to meals and posture and can often be relieved by remedies for indigestion.

Acid is present in the stomach to digest food. Heartburn occurs when small amounts of this acid rise up into the gullet (esophagus) - the tube which carries food from the mouth to the stomach. This is called reflux.

The gullet, unlike the stomach, does not have a protective lining. So when it is exposed to the acid, it can become inflamed and painful.

Acid is present in the stomach to digest food. Heartburn occurs when small amounts of this acid rise up into the gullet (esophagus) - the tube which carries food from the mouth to the stomach. This is called reflux.The gullet, unlike the stomach, does not have a protective lining. So when it is exposed to the acid, it can become inflamed and painful.

Ulcers• What causes peptic ulcers?• The contents of the stomach are acidic. The acid helps to protect the

body from infection and helps break down the food that is eaten. The lining of the stomach and duodenum is covered in mucus (a thick, smooth fluid), which protects it from this acid. An ulcer can result when the stomach produces excess acid or there is insufficient mucus to protect the lining from damage.

• There are several factors that increase a person's risk of getting a peptic ulcer:

• infection with bacteria called Helicobacter pylori (H. pylori) - this is almost always present in people with ulcers, although it's also found in the stomachs of many people without ulcers or indigestion symptoms

• regularly taking certain medicines, particularly aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen and diclofenac

• smoking • drinking alcohol in excess

http://www.lib.uiowa.edu/hardin/md/pepticulcer.html

• -Normal mucosal folds ("rugae") in the gastric body. -Gastric Ulcer-Perforated ulcer

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Acidosis and Alkalosis

• These are two conditions in which the pH of the blood is disturbed beyond the optimum value of 7.41.

• Either condition can be fatal if not corrected.

• Either condition can occur naturally, but the body has a carbonic acid – sodium carbonate buffering system to correct for minor pH disturbances

Acidosis Alkalosis

pH less than 7.35 greater than 7.45

Breathing hypoventilation hyperventilation

Blood Gases O2 (down) CO2 (up) O2 (up) CO2 (down)

Nervous System Slows-coma Speeds up-- convulsions

Treatment Oxygen, BiCarbonate IV Paper Bag HCO3

1- (or mask)