When KCl dissolves in water...

Question

The answer is the K+ ions are attracted to the partially negative oxygen atoms of the water molecule. My question is, is that why does it do this? Would someone be able to explain why this happens when KCl dissolves in water more in depth to help me understand why this process takes place please.

Answer 1

KCl is a crystal and has a crystal lattice structure. You can get a better idea what that looks like if you do a search for "crystal structure of KCl".  When you do this, you'll see that each K⁺ ion is surrounded by (touched by) 6 Cl^- ions and each Cl^- ion is surrounded by (touched by) 6 Na⁺ ions.  This is the structure of KCl.  Now, take a look at a water molecule. Again, if you can't visualize it, look it up.  It has a bent structure (like a V) and the apex is oxygen (O) and the two legs are each hydrogen (H).  The O has two lone pairs of electrons and so is partially negative, while the hydrogens are partially positive. When a water molecule approaches a KCl formula unit (another word for molecule in this case), the K⁺ and O^- are attracted and the bond between the K⁺ and Cl^- breaks.  This is also true for the H⁺ of water and the Cl^- of KCl.  After this happens, each K⁺ and Cl^- ions get surrounded by H2O molecules so they are not likely to rejoin into KCl.  This is referred to as hydration.  The ultimate result of all of this is the KCl dissolves in water.