DISSOCIATION
Separation of inorganic acids , bases or salt into ions in a solution.
ACID
A substance that dissociates into 1 or more hydrogen ions H+ and 1 or more anions.
Because H+ ion is a single proton with 1 positive charge, an acid is referred to as PROTON DONOR.
eg. H2SO4
BASE
A substance that dissociates into 1 or more hydroxide ions OH- and 1 or more cations.
-Removes H+ from a solution.
is therefore a proton acceptor .
eg. NaOH
SALT
When dissolved in water, dissociates into cation and anions
- neither of which is H+ or OH-
Acids and bases react with 1 another to form salts.
eg
HCl + KOH - H+ Cl- + K+ OH-
acid base ions
- KCl + H2O
salt
This is an exchange reaction
In body
Salts such as KCl are electrolytes
- carry electrical currents especially in nerves and muscle tissues.
ACID - BASE BALANCE : THE CONCEPT OF pH
The more hydrogen ions H+ dissolved in a solution, the more acidic the solution.
The more hydroxide ions OH- , the more basic or alkaline the solution.
pH SCALE
A solution's acidity or alkalinity is expressed on the pH scale.
Extends from 0 to 14.
Is based on the concentration of H+ in moles/L.
A pH of 7 means that
- a solution contains 1 ten millionth
= 1 x 107 (0.0000001) of a mole of H+ ions per liter
To convert the value of pH
The negative exponent (-7) is changed to a positive number(7).
eg. A solution with a H+ concentration of 10-6 moles per liter has a pH of 6
The midpoint of pH scle is 7
where concentration of OH- and H+ are equal.
A substance with a pH of 7 is neutral.
eg. H2O
A solution that has more H+ ions than OH- is an acidic solution
-pH below 7
eg. H2SO4
A solution that has more OH- ions than H+ is a
basic or alkaline solution.
-pH above 7.
eg. NaOH
pH VALUE OF CERTAIN SUBSTANCES
Gastric juice 1.2- 3
Lemon juice 2.3
Vinegar 3
Carbonated soft drink 3.0- 3.5
Orange juice 3.5
Vaginal fluid 3.5 - 4.5
Tomato juice 4.2
Coffee 5
Urine 4.6 - 8
Saliva 6.35 - 6.85
Milk 6.8
Distilled/ pure water 7
Blood 7.35- 7.45
Semen 7.20 - 7.60
Cerebrospinal fluid 7.4
Pancreatic juice 7.1 - 8.2
Bile 7.6- 8.6
Milk of magnesia 10.5
Sodium hydroxide / lye 14
Saliva is slightly acidic.
Semen is slightly basic.
Urine is acidic because kidneys help remove excess acid from body.
Homeostatic mechanisms maintain the pH of blood between 7.35 and 7.45
which is slightly more basic than pure water.
If pH of blood below 7.35 = acidosis.
If pH of blood above 7.45 = alkalosis.
BUFFER SYSTEMS
Convert strong acids or bases into weak acids or bases.
Strong acids or bases ionize easily
- contribute many H+ or OH - to a solution
- they can change pH drastically , which can disrupt
the body's metabolism.
Weak acids or bases do not ionize as much
contribute fewer H+ or OH-
Hence they have less effect on the pH.
BUFFERS
The chemical compounds that can convert strong acids or bases into weak ones.
They do so by removing or adding protons(H+)
eg. Carbonic acid- bicarbonate buffer system.
H+ + HCO3- - H2CO3
If there is an excess of H+ (acidic condition) HCO3- can function as a weak base and remove the excess H+.
If there is a shortage of H+ (alkaline condition) , H2CO3 can function as a weak acid and provide needed H+
H2CO3 - H+ + HCO3-
Carbonic acid can act as a weak acid.
Bicarbonate ion (HCO3) can act as a weak base.
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