SALT FORMATION



 

SALT FORMATION

For example, zinc carbonate is placed in hydrochloric acid to produce zinc chloride, water and carbon dioxide gas.

Again, the salt formed is dependent on the cat ion (positively charged ion) present in the carbonate compound and an ion (negatively charged ion) present in the acid. For example; zinc ions are the cat ions while chloride ions are the anions. The two combine to form zinc chloride

Zinc carbonate + hydrochloric acid                                      zinc chloride +   water + carbon dioxide.

ZnCO3                +  2 Hcl                                                                    Zncl2      +    H2O          +   CO2

 

Salt formation:

Zn + 2cl                                                                                                zncl2

Examples

ZnCO3 + H2SO4                                                                                                 ZnCO3  +  H2O  +  CO2

ZNCO3  + H2C2O4                                                                                            ZNC2O4  + H2O  + CO2

The carbon dioxide and water are formed when hydrogen ions, present in the aqueous acid solutions react with carbonate ions.

2 H+ + CO3 2-                                                                                                             H2O   +  CO2

From the above, it is clear that all aqueous acids contain hydrogen ions. ie

Hcl  (aq)                                                                                H+ (aq)  + CL-(aq)

H2SO4                                                                                          H+   +     SO4 2-

CH3COOH                                                                                   2H+   + CH3COO

 

ACID STRENGTH

A strong acid is defined as one that dissociates completely in aqueous solution.

A weak acid is defined as one that dissociates partially in aqueous solution.

The pH value of a solution is related to the number of hydrogen ions present; the higher the number of the hydrogen ions present, the lower the pH value and the stronger the acid.

For example, Hydrochloric acid solution has a low pH value than ethanoic acid because it has more Hydrogen ions than ethanoic acid.

Acids whose aqueous solutions contain a high number of hydrogen ions are therefore strong, while those with few Hydrogen ions are weak acids.

Nitric V acid, hydrochloric, and sulphuric VI acid are examples of strong acids.

Ethanoic, ethanedioic and methanoic acid are examples of weak acids. When weak acids are dissolved in water, very few molecules are converted into ions; most remain in small molecules of unionized particles.



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