The enthalpy changes of formation of the gaseous oxides of nitrogen `(N_(2)O` and `NO)` are positive because of `:`

Options

A. The high bond energy of the nitrogen molecule
B. The high electron affinity of oxygen atoms
C. The high electron affinity of nitrogen atoms
D. The tendency of oxygen to form `O^(2-)`

Answer

To determine why the enthalpy changes of formation of the gaseous oxides of nitrogen (N₂O and NO) are positive, we can analyze the factors involved in their formation. Here’s a step-by-step solution:

### Step 1: Understanding Enthalpy of Formation
The enthalpy of formation (ΔH_f) is the heat change that results when one mole of a compound is formed from its elements in their standard states. Typically, this process releases energy, resulting in a negative enthalpy change.

**Hint:** Remember that a negative ΔH_f indicates that energy is released during the formation of a compound.

### Step 2: Analyzing the Formation of N₂O and NO
The formation of N₂O and NO involves the reaction of nitrogen (N₂) with oxygen (O₂). The balanced reactions are:
- For N₂O: N₂(g) + 1/2 O₂(g) → N₂O(g)
- For NO: N₂(g) + O₂(g) → 2NO(g)

**Hint:** Consider the reactants involved and the type of bonds that need to be broken and formed during these reactions.

### Step 3: Bond Energies
In N₂, there is a strong triple bond between the nitrogen atoms. Breaking this bond requires a significant amount of energy (high bond enthalpy). When N₂ reacts with O₂ to form N₂O or NO, new bonds are formed between nitrogen and oxygen, but the energy released from these new bonds is not sufficient to compensate for the energy required to break the N≡N bond.

**Hint:** Compare the bond energies of the bonds being broken (N≡N) and those being formed (N-O) to understand the energy balance.

### Step 4: Conclusion on Enthalpy Change
Since the energy required to break the strong N≡N bond is greater than the energy released from forming the N-O bonds, the overall process absorbs energy, resulting in a positive enthalpy change for the formation of N₂O and NO.

**Hint:** A positive ΔH_f indicates that the products have higher energy than the reactants, leading to less stability.

### Final Answer
The enthalpy changes of formation of the gaseous oxides of nitrogen (N₂O and NO) are positive because the energy required to break the strong N≡N bond in nitrogen is greater than the energy released from the formation of the N-O bonds.