What test is used where the elements present in the compound are converted from covalent form into the ionic form by fusing the compound with sodium metal?

Lassaigne’s test

The correct answer is option 4. Lassaigne’s test.

The test described, where the elements present in the compound are converted from covalent form into the ionic form by fusing the compound with sodium metal, is known as Lassaigne’s test.

Lassaigne's test, also known as sodium fusion test, is used to detect the presence of halogens (chlorine, bromine, iodine) and nitrogen in an organic compound. In this test, the organic compound is fused with metallic sodium, converting the elements present into ionic forms, which can then be identified through subsequent chemical reactions. This test is particularly useful in identifying the presence of these elements in organic compounds.