Classifications of bases according to strength ( degree of ionization ) and 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 )

Strong bases

Bases which are completely ionized in the water , Their solutions are good conductors of electricity , They are considered as strong electrolytes .

Examples : Potassium hydroxide KOH , Sodium hydroxide NaOH , Barium hydroxide Ba(OH)2 .

Weak bases

Bases which are incompletely ionized in the water , Their solutions are bad conductors of electricity , They are considered as weak electrolytes .

Examples : Ammonium hydroxide NH4OH

Bases

Bases

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 .

Sodium carbonate is from bases because sodium carbonate reacts with acid forming salt and water , Not all bases are alkalis because there are some bases don’t dissolve in the water .

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

Indicators are weak organic acids or bases , their color changes with the change of the solution type .

Indicators are used in identifying the type of solution and determining the end point in titration process between acids and bases .

The following table shows examples of some indicators

Table of indicators

Table of 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 :

Acidic solution

When the monobasic acid dissolves in the water , each molecule gives one proton  H+ , The concentration of H+ > OH , PH value < 7 .

Neutral solution

When NaCl dissolves in the water , The concentration of H+ = OH , PH value = 7 .

Basic solution

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 ) .

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