ΔH for the reaction IF5 (g) → IF3 (g) + F2 (g) is ________ kJ, give the data below.
IF (g) + F2 (g) → IF3 (g) ΔH = 390 kJ
IF (g) + 2 F2 (g) → IF5 (g) ΔH = 745 kJ
A) +1135
B) 1135
C) 35
D) +355
E) +35
1 Answer

You have to flip the second reation because you have to get the IF5 on the reactant side so when you do that you flip the sign on that reaction’s ΔH. So then you have
IF(g) + F2(g) > IF3(g)
IF5(g) > IF(g) +2F2(g)
One of the F2 cancels and the IF(g) cancel so then you have the equation you need.
IF5(g)> IF3(g) + F2(g)
Now you add the ΔH’s together. 390 kJ + 745 kJ = +355 kJ
Source(s): Chem major