Which of the following statement is wrong?

Complex compounds give tests for all the ions presence in them

The correct answer is option (3) Complex compounds give tests for all the ions presence in them.

Complex compounds do not give tests for all the ions present in them. This is because the ligands in a complex compound can coordinate with the metal ion in such a way that the ions present in the complex are not free to be detected by chemical tests.

For example, the complex compound [Co(NH3)6]Cl3 does not give a test for chloride ions. This is because the chloride ions are coordinated to the cobalt ion in the complex, and they are not free to be detected by chemical tests.

The other statements are all correct.

Statement (1) is correct because transition elements have partially filled d orbitals, which makes them more electrophilic and hence more likely to form complexes.

Statement (2) is correct because the groups that satisfy the secondary valencies of a cation in a complex are called ligands. Ligands are usually molecules or ions that have a lone pair of electrons that can be donated to the metal ion.

Statement (4) is correct because double salts exist only in the solid state. When they are dissolved in water, they dissociate into their constituent ions. This is why double salts give tests for all the ions present in them.