Question

Nickel can be purified by producing the volatile compound nickel tetracarbonyl. Nickel is the only metal that reacts with carbon monoxide at room temperature. Assuming this compound is overall neutral, what is the oxidation state of Ni in the compound? Deduce the formula of the compound.

Short answer

The oxidation state of Ni in the compound nickel tetracarbonyl is 0, as the overall oxidation state of CO is also 0. Therefore, the formula of the compound is \(Ni(CO)_4\).

Step-by-step solution

Identifying the oxidation state of carbon monoxide (CO)

First, we need to determine the oxidation state of carbon monoxide (CO). Since oxygen is more electronegative than carbon, it "gains" electrons and has an oxidation state of -2. Carbon needs to "lose" electrons to achieve its formal charge, so its oxidation state is +2. Hence, the overall oxidation state of CO is 0 (+2 for carbon and -2 for oxygen).

Calculating the oxidation state of nickel (Ni)

In the compound, nickel (Ni) is bonded to 4 CO molecules, and the overall charge of the compound is neutral. As we already know, the overall charge of CO is 0. So, we can write the charge equation as: Ni + 4*(0) = 0 This simplifies to: Ni = 0 Thus, the oxidation state of Ni in the compound nickel tetracarbonyl is 0.

Deduce the formula of the compound

Now, we have the oxidation states of Ni and CO in the compound, so we can write the formula of the compound. As Ni has an oxidation state of 0 and the 4 CO molecules together have an oxidation state of (4 * 0), the formula for nickel tetracarbonyl is: Ni (CO)4

Key concepts

Nickel tetracarbonyl

Nickel tetracarbonyl is a fascinating chemical compound where nickel and carbon monoxide come together in a unique way. This compound is significant in the purification process of nickel due to its volatility. Unlike most metals, nickel easily reacts with carbon monoxide at room temperature, forming a gaseous compound.
This specific interaction allows nickel to be separated and purified from other metals. Nickel tetracarbonyl has the chemical formula \( \text{Ni(CO)}_4 \), signifying that one nickel atom is surrounded by four carbon monoxide molecules.

• The formation occurs without any overall charge, making it a neutral compound.
• The attachment of these CO ligands to nickel requires a zero oxidation state for nickel.

This unique chemical structure and property make nickel tetracarbonyl a standout example of metal-carbon monoxide coordination chemistry. This compound is also a crucial intermediate in nickel refining and catalysis.

Carbon monoxide

Carbon monoxide (CO) is a simple yet powerful molecule composed of one carbon atom and one oxygen atom. It's a colorless and odorless gas, well-known for being a byproduct of incomplete combustion. However, it plays an essential role in forming chemical compounds.
In the case of nickel tetracarbonyl, CO acts as a ligand, meaning it binds to the central nickel atom. Each CO molecule brings an oxidation state of zero to the table, thanks to the balance of the oxidation states within CO:

• The oxidation state of oxygen in CO is -2.
• Carbon has an oxidation state of +2, balancing oxygen's -2 oxidation to give the whole molecule an oxidation state of 0.

The strong carbon-oxygen bond in CO is crucial for its ability to donate electron pairs to metals like nickel, forming stable complex compounds in the process.

Neutral compound

A neutral compound has no overall charge, meaning the sum of the individual oxidation states equals zero. Nickel tetracarbonyl is an excellent example of a neutral compound. It's interesting because even though the components have their own charges, they balance each other out to make the entire molecule neutral.
For example, in nickel tetracarbonyl, we have one nickel atom with an oxidation state of zero and four CO ligands, each also with an oxidation state of zero. This results in:

• The total oxidation state for the compound equals zero.
• No extra electrons are added or removed, leading to a stable neutral molecule.

As such, understanding neutral compounds is essential for chemists, especially when predicting how a compound will interact with others or during the purification processes in industries.

Formulating chemical compounds

Formulating a chemical compound involves understanding the elements involved and how they combine to form stable structures. For nickel tetracarbonyl, the process begins with recognizing the essential characteristics of the components involved, namely nickel and carbon monoxide.
Here are the simplified steps taken to formulate such compounds:

• Determine the oxidation states of each element involved.
• Calculate and ensure the sum of all oxidation states equals the desired charge of the compound (in this case, neutral).
• Write the empirical formula that reflects the molecular structure.

The formula \( \text{Ni(CO)}_4 \) was derived using these principles, highlighting the zero oxidation state of nickel and the zero charge state of the compound overall. When formulating chemical compounds, precision in these steps ensures that the resulting substances exhibit the intended chemical properties and interactions.