Why is calcium chloride soluble in water?

Question

I know calcium chloride is soluble in water but i want to know exactly why.. can anyone help? thanks

Answer 1

Picture a force holding the Ca and Cl together.  Then picture water molecules pulling on the Ca and Cl.  If the pull by the water molecules on Ca and Cl is greater than the pull by the Ca and Cl on each other then the CaCl2 will dissociated into hydrated ions in solution.

We can also relate this to the Gibbs free energy.

DG = DH -TDS

The general trend in nature is to increase in entropy.  A crystalline solid dissociating to form three ions in solution is an increase in entropy.  Then -TDS will be negative.  This, along with a negative DH, will ensure that DG is negative, indicating a spontaneous reaction.

Answer 2

calcium  comes upper in reactive series so it is more reactive than hydrogen so displacement reaction takes place and it form calcium hydroxide

Answer 3

Why questions in chemistry are always dependent upon current theory.  Chemists never know with absolute certainty why something happen.

The best answer I can give you depends upon the nature of ionic solids and what happens to ions in solution.  Calcium (II) chloride (CaCl2) as a solid has a tetragonal unit cell, with each Calcium cation surrounded by four chloride anions.  The size of these ions is such that water molecules can easily surround them when they are at the surface of the solid.  This changes the structure of the solid, pulling the ions apart.  This releases energy (heat of hydration or heat of solution) which further separates the ions in the solid (held together by the lattice energy).

Calcium chloride is not only soluble, it is hygroscopic (meaning that it will actually pull water out of moist air).  In doing so, it becomes hydrated and it's structure changes (making the lattice energy smaller).  In fact the solid is also deliquescent (meaning that if given enough time it will absorb enough water to become a liquid solution).

Answer 4

Most metal chlorides are soluble in water except for PbCl2, Hg2Cl2, and AgCl. If a substance is soluble in water, that means that the energy of hydration (energy released when the ions react with water) is greater than the energy of the crystal lattice.