Question

Consider the following enthalpy diagram.

What is the overall enthalpy change DHrxn for the system?
-1,300 kJ
-300 kJ
300 kJ
1,300 kJ

Answer 1

The correct answer this problem is the third option.

Answer 2

Answer:
`\Delta H` for the reaction is 300kJ.

Step-by-step explanation:

By convention:

Energy gained or absorbed is taken as positive and energy released is taken as negative.

In the question,

Reactant A + 2D is absorbing energy of amount 800kJ to reach an intermediate state and at first releasing 200 kJ of energy and then releasing 300 kJ of energy. Thus, total of 500 kJ of energy is released.

So,
`\Delta H_(reaction)` = Energy gained - Energy lost

`\Delta H=(800-500)kJ=300kJ`

Hence,
`\Delta H` for the reaction is 300kJ.