How to predict Ph of A salt in solution ?

True all these salts are neutral except CrCl3. You have to look carefully at the cations. Each cation has what is called a charge density. this is the ratio of charge to volume. cations with a high charge density (like Cr3+ with its triple positive charge) will, when hydrated in solution interact very strongly with the water molecules, and draw the oxygen centers so strongly that one or more of them will lose a proton which will enter solution and make it acidic. thats the explanation. ions with charges of 3+ and higher typically behave this way.