Reactions that immobilize ions in hard water are called

Precipitation reactions

Explanation:

Hard water contain high amount of minerals like calcium and magnesium.  Water is turned hard, when it passes through limestone or chalk deposits that are majorly composed of bicarbonates of magnesium and calcium.

Precipitation reaction refer to the process that solidifies the insoluble ion particles in water. This solid product can be in the form of crystal or in powder form and it settles at the bottom of the water. The soluble products will still remain in the water.

The precipitation reactions is used to remove Calcium and magnesium ions from hard water. During this process, sodium carbonate or washing soda is added into the hard water which immobilize the Calcium and magnesium ions and results in the precipitation of these ions. This is because sodium chloride is solid, it will be removed and we will get soft water left.

Sodium Carbonate+Calcium Chloride  →  Sodium Chloride +Calcium Carbonate

Na2CO3 + CaCl2 → 2NaCl  +CaCO3

Hope it helps!

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.