Enthalpy diagram help

Question

Given that:
Sn(s) + Cl2 (g) → SnCl2 (s); ΔH = - 350 kJ mol-1
and
Sn (s) + 2Cl2 (g) → SnCl4 (s); ΔH = - 542 kJ mol-1
draw a thermal cycle and calculate the enthalpy change for
SnCl2 (s) + Cl2 (g) → SnCl4 (s)

Answer 1

Can't easily draw anything on this site, so you'll have to figure that our yourself.  If you look up Hess' Law, you'll see examples of how to draw such an energy diagram/cycle.

To answer the second part, calculate ∆H, you reverse the first reaction and reverse the sign on ∆H and use second reaction as is, and you get the following:

SnCl2 ====> Sn + Cl2  ∆H = + 350 kJ/mole

Sn + 2Cl2 ====> SnCl4  ∆H = - 542 kJ/mole

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Sn + SnCl2 + Cl2 ===>SnCl4 + Sn + Cl2 and canceling common species, you end up with 

 

SnCl2 + Cl2 ===> SnCl4  and ∆H = -542 + 350 = -192 kJ/mole