Question

Calculate the ΔH (change in enthalpy) for the reaction:

IF(g) → IF(g) + F(g)
Based on the data below:
IF(g) + F(g) → IF(g); ΔH = -390 kJ
IF(g) + 2F(g) → IF(g); ΔH = -745 kJ

A) -355 kJ
B) -745 kJ
C) -135 kJ
D) 135 kJ

Answer 1

The enthalpy change (∆H) for the decomposition of IF into IF and F atoms is -355 kJ, obtained by subtracting the enthalpy of the first reaction from the second reaction provided.

Step-by-step explanation:

The goal is to calculate the ∆H (change in enthalpy) for the decomposition of IF into IF and F atoms based on the two given reactions. To solve this, ensure that the stoichiometry matches the reaction we're interested in, allowing us to derive the correct enthalpy change. We use the given reactions and their ∆H values:

1. IF(g) + F(g) → IF(g); ∆H = -390 kJ
2. IF(g) + 2F(g) → IF(g); ∆H = -745 kJ

Since the reaction we're analyzing is simply the decomposition of IF, we can calculate the enthalpy change by subtracting the enthalpy of the first reaction from the second one, as such:

∆H for IF(g) → IF(g) + F(g) = ∆H for [IF(g) + 2F(g) → IF(g)] - ∆H for [IF(g) + F(g) → IF(g)]

∆H for decomposition = -745 kJ - (-390 kJ)

∆H for decomposition = -355 kJ

The correct answer to the problem is -355 kJ, which is answer choice A).