What is a compound called that has the ability to soak up large amounts of water?

Hygroscopic substances

Explanation:

Hygroscopic compounds are those that absorb moisture and a large amount of water and they become wet. They should not be confused with deliquescent substances that absorb water and forms solution.

Hygroscopic substances froms pasty substances and not solution while the liquid ones only becomes diluted. Examples are sodium trioxonitrate(v) (NaNO₃), copper (ii) oxide CuO, and concentrated tetraoxosulphate (vi) acid (H₂SO₄)

- aluminum and copper chloride.

- the chloride ion to separate the aluminum from the oxygen so that the aluminum can react with the copper ions (and the water molecules).