Q) Since HCL has strong covalent bonds, why is it that they dissociate easily into H+ ions and Cl- ions when put in water?
Answers:
In GCE O Level education, this question is usually not posed. In Junior Collleges, detailed explanation will be given in general chemistry classes.
Suggested Answer:
The hydrogen chloride molecule HCl is a simple diatomic molecule consisting of a hydrogen atom H and a chlorine atom Cl connected with a covalent single bond. Since the chlorine atom is much more electronegative than the hydrogen atom, the covalent bond between the atoms is quite polar. Consequently the molecule has a large dipole moment with a negative partial charge ?- at the chlorine atom and a positive partial charge ?+ at the hydrogen atom. In part due to its high polarity, HCl is very soluble in water (and in other polar solvents).
Upon contact with water, it immediately ionizes, forming hydronium cations H3O+ and chloride anions Cl- through a reversible chemical reaction with the water:
HCl + H2O –> H3O+ + Cl?
The resulting solution is called hydrochloric acid and is a strong acid.
To Your Academic Success in Chemistry,
Sean Chua
Master Trainer @ SimpleChemConcepts.com
isn’t it because HCL is a strong acid that it completely dissociates in water?
Hi hsu myat thazin,
Are you a local student in Singapore?
Or are you taking GCE O Level Examinations?
Acids are indeed covalent compounds (we usually call them molecular compounds). This can be verified based on the Dot-and-Cross Diagrams that we normally draw for HCl – which shows H and Cl atoms sharing electrons in order to achieve Noble Gas Configurations.
But as what i have mentioned above, HCl do dissociates in the pressence of water due to this term called “electronegativities”. This is not required / covered in GCE O Levels & equivalent basic chemistry examinations.
Hope this explanation helps.
To Your Academic Success in Chemistry,
Sean Chua
Master Trainer @ SimpleChemConcepts.com
Author of Up Your Chemistry Grades Now! book
So, acids are covalent compounds that produce ions? I thought covalent compounds do not have any ions. Are their structure like normal simple covalent molecules?