Question

What are the ions present in this compound? \[A{l_2}{(S{O_4})_3}\]

Answer 1

Hint: As we know that when any compound is dissolved in water, the ions are dissociated from its compound but remember the reaction must not violate the law of conservation of mass.

Complete answer:
Law of conservation of mass: In a balance chemical equation, the mass of reactants is equal to the mass of products.
In the given compound, the \[A{l_2}{(S{O_4})_3}\] dissociation occurs in water as,
\[A{l_2}{(S{O_4})_3} \to 2A{l^{3 + }}\left( {aq} \right) + 3S{O_4}^{2 - }\left( {aq} \right)\]
So, after dissociation, there are the two aluminium ions and three sulphate ions which obeys the law of conservation of mass because in the above equation the number of aluminium atoms are equal in both sides (reactant and product) and number of sulphate groups also equal on both sides.
As we can see in the above equation, the dissociation occurs due to the breaking of ionic force which is present between the aluminium cation and sulphate anions of aluminium sulphate compound.

So the ions present in this compound are $Al^{3+}$ and $SO_4^{2-}$.

Note: The compound \[A{l_2}{(S{O_4})_3}\] is soluble in water but insoluble in organic compounds. The solubility of compounds decreases if they have small hydration energy. As we go down the group there is decrease in solubility of sulphate compounds because the size of cation and anion are larger hence the compounds have small lattice energy and small hydration energy.