如果HCl係共價化合物,咁點解係水溶液佢可以導電??

HCl in air is called hydrogen chloride, it is a covalent compound, it has a simple molecular structure. HCl exists in air in form of molecules. So, it cannot conduct electricity as it has no delocalized electrons or mobile ions.

Nevertheless, when HCl molecules dissolve in water, HCl molecules will ionize itself to give hydrogen H+ ions and chloride Cl- ions. HCl in water is called hydrochloric acid. Since it is a strong acid, it will completely ionize in water to give H+ ion as the only positive ion.

From now on, mobile ions are present in HCl (hydrochloric acid), so it can conduct electricity by means of mobile ions. Note the hydrochloric acid is an ionic compound.

This is a common charactristic for acid. Water MUST be present for an acid to show its acidic property. Initially, acid is a covalent compound, when it dissolves in water, it becomes an ionic compound.

HCl 係ionic compound
唔係covalent
所以係水可以導電