Calculate the enthalpy change for the reaction NO(g) + O(g) → NO₂(g)
From the following data:
NO(g) + O₃(g) → NO₂(g) + O₂(g) ΔH = −198.9 kJ
O₃(g) → 1.5O₂(g) ΔH = −142.3 kJ
O₂(g) → 2O(g) ΔH = 495.0 kJ

Question

Quizplus · Accepted Answer

To find the enthalpy change for the reaction NO(g) + O(g) → NO₂(g), we need to manipulate the given reactions and their ΔH values to match the target reaction. The given reactions are:1. NO(g) + O₃(g) → NO₂(g) + O₂(g), ΔH = −198.9 kJ2. O₃(g) → 1.5O₂(g), ΔH = −142.3 kJ3. O₂(g) → 2O(g), ΔH = 495.0 kJTo get the target reaction, we need to reverse reaction 3 (which changes the sign of ΔH to -495.0 kJ) and add it to reaction 1. We also need to subtract half of reaction 2 (which is -142.3 kJ / 2 = -71.15 kJ, because we only need 0.5 O₂(g) to cancel out with the O₂(g) produced in reaction 1). So, the total ΔH for the target reaction is:ΔH = (-198.9 kJ) + (-495.0 kJ) + (-71.15 kJ) = -765.05 kJHowever, since none of the provided options match this calculation, it appears there was a mistake in my calculation process. Let's correct that:The correct process involves adding the first and second reactions directly and then subtracting the reverse of the third reaction (which involves halving its ΔH because we only need 0.5 O₂(g) from the third reaction to cancel out with the O₂(g) produced in the first reaction). So, the correct calculation should be:ΔH = (-198.9 kJ) + (-142.3 kJ / 2) + 495.0 kJ / 2This gives us:ΔH = -198.9 kJ - 71.15 kJ + 247.5 kJ = -22.55 kJGiven the mistake in the recalculation and the options provided, it seems there was an error in interpreting the reactions and their contributions to the overall enthalpy change. The correct approach is to consider how each given reaction contributes to forming the desired products and reactants from the given data, ensuring the stoichiometry aligns with the target reaction. Given the error in the recalculated approach and the options provided, let's reassess the steps to align with the options given:1. The first reaction is used directly.2. The second reaction needs to be used to generate O₂(g) from O₃(g), which indirectly contributes to the formation of O(g) through the reversal of the third reaction.3. The third reaction's ΔH needs to be adjusted for the amount of O₂(g) actually involved in the target reaction.The correct interpretation should involve directly using the enthalpies from the given reactions to match the stoichiometry of the target reaction, considering the need to reverse or adjust the given reactions. The mistake in the detailed calculation above indicates a misunderstanding of how to properly combine the given reactions to achieve the target reaction's stoichiometry and enthalpy change. Given this, the correct answer should reflect the proper combination and manipulation of the given reactions and their ΔH values to match the target reaction, which was not accurately represented in the detailed explanation provided. The correct enthalpy change calculation involves accurately accounting for the enthalpy changes of the given reactions, including any necessary reversals or adjustments for stoichiometry, to directly derive the enthalpy change of the target reaction.

Calculate the Enthalpy Change for the Reaction NO(g) + O(g)