Which bond of the above in a particular formula unit or molecule is stronger?

Personally, I think covalent bond is stronger.

Many ionic substance dissolve in water to give ions out but no molecules, like oxygen , hydrogen....

I believe that the ionic bond is stronger. Just because something dissolves into separate ions in water does not mean it has a weak bond. The amount of energy needed to break an ionic bond is pretty high compared to a covalent bond. That is why it requires so much energy to melt an ionic solid. When the solid melts, the ionic bonds between the cations and anions need to be broken apart.

 

Another thing to consider is that water is composed of covalent bonds, but it's VERY easy to break those bonds like any alkali metal will, or any other substance which reacts with water. I'll have to look up the exact numbers to be 100% sure on this.

i will second that; ionic bonds are much stronger than covalent bonds (usually)

Why do water molecules cannot attract and seperate the phosphorus trichloride?

It's polar molecule, attraction is quite strong.....

Actually, covalent bonds are stronger than ionic ones. I think you fellows are forgetting that covalent compounds are usually composed of molecules, which aren't covalently bound to one another, but rather held together by intermolecular forces of attraction. These forces are much weaker than the ionic attractions that hold together the crystalline structure of an ionic compound, so ionic compounds will have much higher melting points than covalent molecular compounds.

i understand the wisdom in that statement, but that does not disprove the statement that ionic bonds are stronger than covalent bonds, as you only explained one reason for the high melting/boiling points of ionic compounds compared to covalent compounds, but did not actually explain how covalent bonds are stronger. could you clear this up? i still believe that ionic bonds are stronger than covalent bonds as of now