Question

Look up the energies for the bonds in CO and \(\mathrm{N}_{2}\). Although the bond in CO is stronger, CO is considerably more reactive than \(\mathrm{N}_{2}\). Give a possible explanation.

Short answer

The bond energy for CO is approximately \(1072 \: \text{kJ/mol}\), while for N2, it is approximately \(945 \: \text{kJ/mol}\). Although CO has a stronger bond, it is more reactive than N2 due to its polar nature, resulting from the difference in electronegativity between the carbon and oxygen atoms. In contrast, N2 has a non-polar covalent bond due to the equal electronegativity of the two nitrogen atoms, making it more stable and less reactive.

Step-by-step solution

Find the bond energies for CO and N2

First, let's find the bond energies for both CO and N2 molecules. The bond energy is the energy required to break a chemical bond and form separate, isolated atoms. It can typically be found in tables or online sources. CO (Carbon Monoxide) – Bond energy: \( \approx 1072 \: \text{kJ/mol} \) N2 (Dinitrogen) – Bond energy: \( \approx 945 \: \text{kJ/mol} \) From the data, we can see that the bond in CO is stronger than the bond in N2.

Discuss possible explanation for CO's reactivity

Although CO has a stronger bond, it is known to be more reactive than N2. A potential explanation for this phenomenon could be the difference in their molecular structure and the electronegativity of their constituent atoms. In the CO molecule, the carbon (C) atom has a lower electronegativity (2.55) compared to the oxygen (O) atom (3.44). This difference in electronegativity leads to a polar covalent bond where electrons are shared unequally between C and O. As a result, there is a partial positive charge on the carbon atom and a partial negative charge on the oxygen atom. This makes CO more susceptible to attack by other molecules due to its polar nature. On the other hand, the N2 molecule is composed of two nitrogen (N) atoms that share the same electronegativity (3.04). Therefore, the electrons in an N2 molecule are shared equally between the two nitrogen atoms, leading to a non-polar covalent bond. This makes the N2 molecule more stable and less likely to react with other molecules. In conclusion, although CO has a stronger bond than N2, CO is more reactive due to its polar nature resulting from the differences in electronegativity between the carbon and oxygen atoms. Conversely, the non-polar nature of N2 gives it more stability and less reactivity.

Key concepts

Chemical Bond Energies

Understanding chemical bond energies is essential for exploring why some compounds are more reactive than others. The bond energy is the measure of the strength of a chemical bond. It represents the amount of energy needed to break the bond and separate the atoms into individual gaseous atoms.

When we examine molecules such as CO and N2, we look at the bond energies to get a sense of their chemical stability. With a bond energy of approximately 1072 kJ/mol, CO has a strong bond, even stronger than N2, which is approximately 945 kJ/mol. Generally, one might assume that a molecule with a higher bond energy is less reactive since it's harder to break the bond. However, this is not the only factor at play, as we will see with the reactivity of CO compared to N2.

CO and N2 Reactivity

The reactivity of a molecule is influenced by more than just bond energies. Carbon monoxide (CO) displays more reactivity than nitrogen (N2) despite having a stronger bond.

Electronegativity Differences and Molecular Structure

One of the main reasons is the difference in electronegativity between the atoms that form their respective molecules. In CO, the significant electronegativity difference creates a polar covalent bond. This polarization introduces areas of positive and negative charges, which can attract other reactants, elevating CO's propensity to engage in chemical reactions.

In contrast, N2's non-polar covalent bond results from two identical nitrogen atoms sharing electrons equally, making the molecule non-reactive. The triple bond tying the nitrogen atoms together also gives N2 a unique stability, despite its lower bond energy when compared to CO.

Polar and Non-Polar Covalent Bonds

The distinction between polar and non-polar covalent bonds lies in how electrons are shared between the atoms. A non-polar covalent bond occurs between atoms of the same or similar electronegativity, resulting in an equal share of electrons. Molecules like N2 exemplify non-polar covalent bonds, giving them low reactivity due to a lack of poles or charges to interact with other molecules.

Conversely, a polar covalent bond forms when atoms with different electronegativities come together. The unequal sharing of electrons in molecules such as CO leads to partial charges, with the more electronegative atom holding a partial negative charge. This imbalance distinguishes these molecules as more chemically active or reactive, ready to participate in reactions where charge separation can facilitate bond formation or cleavage.