Explain why alchemy is not as reliable as modern day science

Alchemy is the forerunner of modern chemistry practiced during the medieval times. Chemists of those times were known and called alchemists.

These chemists had a very shallow knowledge of chemistry but were able to produce a wide range of chemicals.

Alchemy predates the scientific method. Modern science is investigative and relies on the precepts of detailed and methodical process. Modern day chemistry is a vertiginous study with more depth. It seeks to provide details into reasons why certain chemical matter exists as they are. Or how combinations in reactions takes place. Alchemy does not follow the scientific method in its investigation