Saturday, 19 January 2013

INORGANIC ACIDS, BASES AND SALTS

INORGANIC ACIDS, BASES AND SALTS


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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