Properties of Acids:
1. taste sour or tart
2.
feels like water (to the touch)
3. Sting
4. electrolytes – conduct electric current
5. react with metals
6. turns indicator paper red
Properties of Bases:
1. bitter taste
2. feel slippery
3. electrolytes – conduct electric current
4. do not react with metals
5. turns indicator paper blue
Arrhenius Acids and Bases:
1. Arrhenius Acid –substances that release hydrogen (H+) ions when dissolved in water
2. Arrhenius Base – substances that generate hydroxide ions (OH-)when dissolved in water
Neutralization:
Acids & Bases react so that the properties of both are lost, to form water and a salt
--- The HCl molecule dissociates into its constituent ions: H+ and ClThe hydrogen ion only one simple proton
Why do acids and bases neutralize each other?
The H+ from the acid mixes with the OH- from the base to produce water, H2O
What is the general equation for a neutralization reaction?
acid + base  water + salt (HCl + NaOH  H2O + NaCl)
Brønsted-Lowry (B-L) Acids and Bases:
1. Name two things that were wrong with the Arrhenius definitions of acids and bases?
-
They could not explain why a number of products like baking soda (Na2CO3) acted like a
base but contained no hydroxide (OH-) ions
-
Definitions are limited to reactions of acids and bases in water
2. Brønsted-Lowry Acids – any substance that can donate a hydrogen (H+) ion (aka: proton)
3. Brønsted-Lowry Bases – any substance that accepts a hydrogen (H+) ion (aka: proton)
4. This definition expands the number of substances that can be acids and bases and shows the
5. Under to the B-L definition, both acids and bases are related to the concentration of H+ ions
(acids increase the concentration by donating protons ; bases decrease the concentration by
accepting them)
6. Therefore, the acidity or basicity of something can be measured by the proton (H+ ion)
concentration
Strong vs. Weak
1. Strong acid – readily transfers H+ ions to water; the more complete the transfer of H+ ions, the
stronger the acid
Example: HCl – more than 99% of the H+ ions from HCl are transferred to water to form H3O+
ions
2. Weak acid – does not transfer/donate H+ ions as readily in water
Example: vinegar, CH3COOH – only 0.4% of the H+ ions from CH3COOH are transferred to
water; 99.6% does not dissociate
3. Strong base – substances which have the strongest attraction for H+ ions
Example: Ca(OH)2
4. Weak base – only partially react with water/ partially attract H+ ions
Conjugate Acids-Base Pairs
Example: H+ and HCO3- (differ by only one proton)
There is an inverse relationship between the strength of an acid and its conjugate base: the stronger
the acid, the weaker its conjugate base (and vice versa)
The pH Scale
Water can act like and acid or a base:
Acts like acid - H2O donates H+ to become OHActs like base – H2O accepts H+ to become H3O+
The amount of H3O+ ions in pure water is 10-7 moles/liter
The pH scale is a the measurement of H3O+ ions in the solution
What is the pH concentration range? 10-1 through 10-14
Where does the pH number come from? The exponent
What is the pH of water? 7
All of the solutions that are lower than 7 are acids; all of the solutions higher than 7 are bases
pH in the Chemistry of Nature
Water can act like and acid or a base:
1. Agriculture – most plants prefer neutral soil, pH of farmer field is very important
2. Environment –
Acid Rain – most rain water has a pH between 6-7; rainfall with a pH below 5.6
3. Health – pH of saliva, stomach acids, and blood (pH must be between 7.35 and 7:45)
Buffers – in the human body in order to resist changes in pH
Quiz:
1. True
6. Hydrogen ions
2. False
7. True
3. Neutralization
8. False
4. False
9. True
5. True
10. Acid Rain