Classifications of bases according to strength (degree of ionization) & molecular structure
Bases can be classifies according to strength ( degree of ionization ) and molecular structure , Bases are classified according to their degree of ionization ( dissociation ) into strong bases and weak bases .
Classifications of bases according to strength ( degree of ionization )
Examples : Potassium hydroxide KOH , Sodium hydroxide NaOH , Barium hydroxide Ba(OH)2 .
Examples : Ammonium hydroxide NH4OH
Classifications of bases according to molecular structure
Bases are classified according to their molecular structure into :
Metal oxides such as Iron ( II ) oxide FeO and Magnesium oxide MgO.
FeO ( s ) + 2HCl ( aq ) → FeCl2 + H2 O ( l )
Metal hydroxides such as Calcium hydroxide Ca(OH)2 , Sodium hydroxide NaOH .
Ca(OH)2 ( aq ) + H2SO4 ( aq ) → CaSO4 ( aq ) + 2 H2 O ( l )
Metal carbonates such as potassium carbonate K2CO3 and Sodium carbonate Na2CO3 .
K2CO3 ( s ) + 2HCl ( aq ) → 2KCl ( aq ) + H2 O ( l ) + CO2 ( g )
Metal bicarbonates such as potassium bicarbonate KHCO3 and Sodium bicarbonate NaHCO3 .
KHCO3 ( s ) + HCl ( aq ) → KCl ( aq ) + H2 O ( l ) + CO2 ( g )
The bases that dissolve in the water are called Alkalis , Alkali is a base that dissolves in the water and gives hydroxide ion ( OH−), So, the alkalis are a part of the bases and therefore, we can say that : all alkalis are bases and not all bases are alkalis .
Detecting acids and bases
The aqueous solutions are divided into three types which are Acidic solutions , Alkaline solutions and Neutral solutions .
There are two methods for identifying these solutions which are Indicators and pH-meter .
Using the indicators for identifying the aqueous solutions
The following table shows examples of some indicators
Ant and bee bites have an acidic effect , and can be treated by using sodium bicarbonate solution , whereas the wasp and jelly fish have a basic effect and can be treated by using vinegar .
The color of indicator changes with the change of the solution type because the color of non-ionized indicator is different from the color of ionized indicator in different solutions .
Phenolphthalein can not be used to differentiate between the acidic and the neutral medium because it has the same color ( colorless ) in both media .
Using the hydrogen exponent pH for identifying the aqueous solutions
The hydrogen exponent pH is a way to express the degree of acidity or alkalinity of a solution , pH value expressed by positive numbers range from 0 to 14 , pH value can be detected by pH paper tape and pH-meter .
The pH value depends on the concentration of positive hydrogen ions ( H+ ) and negative hydroxide ions ( OH− ) in the solutions as follows :
When the monobasic acid dissolves in the water , each molecule gives one proton H+ , The concentration of H+ > OH− , PH value < 7.
When NaCl dissolves in the water, The concentration of H+ = OH− , PH value = 7 .
When NaOH dissolves in the water , each molecule gives one hydroxide ion , The concentration of H+ < OH− , PH value > 7 .
Vinegar , lemon and tomato juices are acidic solutions ( pH < 7 ) .
Washing soda , detergents and glair are basic substances ( pH > 7 ) .