Given the standard enthalpy changes for the following two reactions:
(1) 2Ni+O2 -> 2NiO ΔH=-479.4kj
(2) 2Zn+O2 -> 2ZnO ΔH=-696.6kj
What is the standard enthalpy change for the following reaction?
(3) NiO+Zn -> Ni+ZnO ΔH=?
Standard enthalpy change =_________ kJ
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To find the standard enthalpy change for reaction (3), we can use the enthalpy changes of reactions (1) and (2).
Since reaction (1) gives us the enthalpy change for the formation of 2 moles of NiO, we can double the enthalpy change value:
2Ni + O2 -> 2NiO ΔH = -479.4 kJ
2(ΔH) = 2(-479.4 kJ) = -958.8 kJ
Similarly, since reaction (2) gives us the enthalpy change for the formation of 2 moles of ZnO, we can double the enthalpy change value:
2Zn + O2 -> 2ZnO ΔH = -696.6 kJ
2(ΔH) = 2(-696.6 kJ) = -1393.2 kJ
Now let's add the two reactions together to get reaction (3):
2NiO + 2Zn -> 2Ni + 2ZnO
To find the enthalpy change for reaction (3), we can add the enthalpy change values for reactions (1) and (2):
ΔH(3) = ΔH(1) + ΔH(2)
ΔH(3) = -958.8 kJ + (-1393.2 kJ)
ΔH(3) = -2352 kJ
Therefore, the standard enthalpy change for reaction (3) is -2352 kJ.
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