Answer to Question #35788 in Inorganic Chemistry for Rachel

Question #35788
Given the following thermochemical equations: X2 + 3Y2 ----&gt; 2XY3 ^H1= -370 kJ X2 + 2Z2 ----&gt; 2XZ2 ^H2= -170 kJ 2Y2 + 2Y2Z -----&gt; 2Y2Z ^H3= -280 kJ Calculate the change in enthalpy for the following reaction: 4XY3 + 7Z2 -----&gt; 6Y2Z + 4XZ2 change H= ________ kJ
The change in enthalpy for the reaction equals: delta H = sum (delta H) of products - sum (delta H) of reagents.
For reagents and products of the following reaction:
delta H (XY3) = -370 kJ / 2 = -185 kJ.
delta H (XZ2) = -170 kJ / 2 = -85 kJ.
delta H (Y2Z) = -280 kJ / 2 = -140 kJ.
delta H (Z2) = 0

delta H (for the reaction) = 6*(-140 kJ) + 4*(-85 kJ) - 4*(-185)-0 = -840 kJ - 340 kJ + 740 kJ = -440 kJ.

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Assignment Expert
07.03.19, 14:16

Dear Jaime,

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Jaime
04.03.19, 04:11

Why is delta Z2 = 0??

Assignment Expert
14.09.15, 16:27

According to Hess's Law the change in enthalpy for the reaction equals: delta H = sum (delta H) of products - sum (delta H) of reagents.
For reagents and products of the following reaction:
delta H (XY3) = -370 kJ / 2 = -185 kJ.
delta H (XZ2) = -170 kJ / 2 = -85 kJ.
delta H (Y2Z) = -280 kJ / 2 = -140 kJ.
delta H (Z2) = 0

delta H (for the reaction) = 6*(-140 kJ) + 4*(-85 kJ) - 4*(-185)-0 = -840 kJ - 340 kJ + 740 kJ = -440 kJ.