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Consider the reaction pathway below - Scottish Highers Chemistry - Question 22 - 2022
Question 22
Consider the reaction pathway below. $$\Delta H = -210 \text{ kJ mol}^{-1}$$ $$\Delta H = -50 \text{ kJ mol}^{-1}$$ $$\Delta H = +86 \text{ kJ mol}^{-1}$$ Accord... show full transcript
Worked Solution & Example Answer:Consider the reaction pathway below - Scottish Highers Chemistry - Question 22 - 2022
Step 1
According to Hess' law, the \( \Delta H \) value from Z to Y:
Answer
To determine the ( \Delta H ) value for the reaction from Z to Y, we can use the enthalpy changes given in the reaction pathway using Hess' law, which states that the total enthalpy change for a reaction is the sum of the enthalpy changes for the individual steps.
- From W to Z: ( \Delta H = -210 \text{ kJ mol}^{-1} )
- From Z to X: ( \Delta H = 50 \text{ kJ mol}^{-1} )
- From X to Y: ( \Delta H = 86 \text{ kJ mol}^{-1} )
The overall ( \Delta H ) can be calculated as follows:
[ \Delta H_{Z \to Y} = \Delta H_{W \to Z} + \Delta H_{Z \to X} + \Delta H_{X \to Y} ] [ \Delta H_{Z \to Y} = (-210) + (50) + (86) ] [ \Delta H_{Z \to Y} = -210 + 50 + 86 = -74 \text{ kJ mol}^{-1} ]
Thus, the answer is B +74.