Ionic & Covalent?

Question

Do you think ionic substances in solution are apt to react more or less rapidly than covalent substances? Why?

Answer 1

Ionic substances in (water) solution are already broken apart by the water molecules and are therefore ready to join with another ion by ionic attraction.

Covalent substances in (water) solutions are not necessarily broken apart and in order for a chemical reaction to take place, bonds must first be broken for +/- parts of the compounds to exchange places. This often times needs to have a net input of energy to get going.

CHEMISTRY TEACHER

Answer 2

Ionic or covalent bonding may have little to do with the rate of a reaction in solution or even in a solid.

Generally speaking, most chemists would tell you that ionic substances have already separated into cations and anions when they were dissolved and therefore should react much faster. This is using common logic and not necessarily chemical experimental evidence.

Consider a solution of Hydrogen gas (covalently bonded) dissolved in Chlorine gas (also covalently bonded) prepared in the dark. Upon exposure to UV light, a violent explosion will take place converting virtually all of the mixture into Hydrogen chloride gas in just a fraction of a second.

Consider the compound used in explosive primer cord. This is a covalently bonded compound. The reaction (explosion) takes place at many feet per second. The explosion of nitroglycerin (another covalently bonded compound) is also very rapid.

To get very technical (or provide your teacher or instructor some food for thought): In aqueous solution a zero order reaction of a covalent substance will often react faster than than ionic compounds which have second order reaction rates. See the materials on kinetics below.