Question

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

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

Answer 1

You can do it like this:

Explanation:

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:

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`