You are given the following two equations. How do you calculate #DeltaH# for this reaction: #Sn(s) + 2Cl_2(g) -> SnCl_4 (l)#?

Question

#Sn(s) + Cl_2(g) -> SnCl_2(s)#
#DeltaH = -325 kJ #
#SnCl_2(s) +Cl_2 (g) -> SnCl_4(l)#
#DeltaH = -186 kJ#

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Answer 1 · 2016-07-16T17:29:02

You can do it like this:

We can apply Hess' Law. This states that the overall enthalpy change for a reaction is independent of the route taken.

It helps to use an energy level diagram:

MF Docs

From this you can see that the route in red is equal in energy to the route in blue:

#:.##sf(DeltaH=-325-186=-511color(white)(c)kJ#