But before we get in to why this happens, we must first take a look at the components involved. Silver nitrate is a caustic chemical compound with the formula AgNO 3. Interestingly, it was previously known as lunar caustic by ancient alchemists who associated silver with the moon. Silver nitrate is highly soluble in water and other solvents. It is also less sensitive to light than its silver halide relatives, and is made by dissolving large amounts of silver in nitric acid.
Even though silver nitrate is poisonous if ingested, it has a variety of applications in medicine where it is used for its antiseptic properties. Silver nitrate is also used as the forerunner in most silver compounds, including those used in photography.
This is because its natural form is directly usable. Copper has weak metallic bonds, which is why it is one of the more ductile metals. While copper is known for its reddish colour, it is also recognised for its green pigment — think of the Statue of Liberty, for example.
This green layer is actually a protective coating known as patina. It forms when copper has been exposed to air for a long period of time, and provides protection against further corrosion. When a copper wire is introduced into an aqueous silver nitrate solution, a single replacement reaction occurs. Problem: When silver nitrate reacts with copper II chloride, silver chloride and copper II nitrate are produced.
Zinc is more reactive than Cu and Fe metal. Iron displaces copper from its solution. Copper is a reddish-brown metal, widely used in plumbing and electrical wiring; it is perhaps most familiar to people in the United States in the form of the penny.
Although since , pennies are actually made of zinc surrounded by a paper-thin copper foil to give them the traditional appearance of pennies. When the solution is diluted with water, water molecules displace the nitrate ions in the coordinate sites around the copper ions, causing the solution to change to a blue color.
In the following demonstration, a balled-up piece of thin copper wire is added to about mL of concentrated nitric acid; once the copper is added the evolution of nitrogen dioxide occurs quickly. Once all of the copper has reacted, the solution is diluted with distilled water, changing the solution from a dark brown to a pale blue color.
This demonstration can be done with copper in the form of shot, pellets, thicker wire, or bars, but is a great deal slower than with copper wire. Ira Remsen founded the chemistry department at Johns Hopkins University, and founded one of the first centers for chemical research in the United States; saccharin was discovered in his research lab in Like many chemists, he had a vivid "learning experience," which led to a heightened interest in laboratory work:.
While reading a textbook of chemistry I came upon the statement, "nitric acid acts upon copper. Copper was more or less familiar to me, for copper cents were then in use. I had seen a bottle marked nitric acid on a table in the doctor's office where I was then "doing time. They do this because of the presence of splitting between the energy levels in the d-orbitals on the central in this case Cu atom. In the bonding to ligands such as NO 3 and H 2 O to form an octahedral complex, typically the dz 2 and dx 2 -y 2 orbitals on the central atom are pushed up in energy slightly in comparison to the other d-orbitals creating a small gap in energy between the these two sets of d-orbitals.
This gap is sometimes small enough that visible light can be absorbed to pass electrons back and froth between the two energy levels. What doesn't get absorbed comes out as our color.
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