Matter either loses or absorbs energy when it changes from one state to another. For example, when matter changes from a liquid to a solid, it loses energy. The opposite happens when matter changes from a solid to a liquid. For a solid to change to a liquid, matter must absorb energy from its surroundings
Answer : The enthalpy of the given reaction will be, -1048.6 kJ
Explanation :
According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.
The main reaction is:
![\Delta H=?](https://tex.z-dn.net/?f=%5CDelta%20H%3D%3F)
The intermediate balanced chemical reactions are:
(1)
![\Delta H_1=-241.8kJ](https://tex.z-dn.net/?f=%5CDelta%20H_1%3D-241.8kJ)
(2)
![\Delta H_2=+461.9kJ](https://tex.z-dn.net/?f=%5CDelta%20H_2%3D%2B461.9kJ)
(3)
![\Delta H_3=-92.3kJ](https://tex.z-dn.net/?f=%5CDelta%20H_3%3D-92.3kJ)
(4)
![\Delta H_4=-789.1kJ](https://tex.z-dn.net/?f=%5CDelta%20H_4%3D-789.1kJ)
(5)
![\Delta H_5=-44.0kJ](https://tex.z-dn.net/?f=%5CDelta%20H_5%3D-44.0kJ)
Now reversing reaction 2, multiplying reaction 3 by 4, reversing reaction 1 and multiplying by 2, reversing reaction 5 and multiplying by 2 and then adding all the equations, we get :
(1)
![\Delta H_1=2\times 241.8kJ=483.6kJ](https://tex.z-dn.net/?f=%5CDelta%20H_1%3D2%5Ctimes%20241.8kJ%3D483.6kJ)
(2)
![\Delta H_2=-461.9kJ](https://tex.z-dn.net/?f=%5CDelta%20H_2%3D-461.9kJ)
(3)
![\Delta H_3=4\times -92.3kJ=-369.2kJ](https://tex.z-dn.net/?f=%5CDelta%20H_3%3D4%5Ctimes%20-92.3kJ%3D-369.2kJ)
(4)
![\Delta H_4=-789.1kJ](https://tex.z-dn.net/?f=%5CDelta%20H_4%3D-789.1kJ)
(5)
![\Delta H_5=2\times 44.0kJ=88.0kJ](https://tex.z-dn.net/?f=%5CDelta%20H_5%3D2%5Ctimes%2044.0kJ%3D88.0kJ)
The expression for enthalpy of main reaction will be:
![\Delta H=\Delta H_1+\Delta H_2+\Delta H_3+\Delta H_4+\Delta H_5](https://tex.z-dn.net/?f=%5CDelta%20H%3D%5CDelta%20H_1%2B%5CDelta%20H_2%2B%5CDelta%20H_3%2B%5CDelta%20H_4%2B%5CDelta%20H_5)
![\Delta H=(483.6)+(-461.9)+(-369.2)+(-789.1)+(88.0)](https://tex.z-dn.net/?f=%5CDelta%20H%3D%28483.6%29%2B%28-461.9%29%2B%28-369.2%29%2B%28-789.1%29%2B%2888.0%29)
![\Delta H=-1048.6kJ](https://tex.z-dn.net/?f=%5CDelta%20H%3D-1048.6kJ)
Therefore, the enthalpy of the given reaction will be, -1048.6 kJ
Personally I think b is the best answer but if not b then A
Answer:
Pure substances can be classified as chemical compounds or elements.