The following reaction is carried out on an industrial scale for the production of thionyl chloride, a chemica

Question

The following reaction is carried out on an industrial scale for the production of thionyl chloride, a chemical used in the manufacture of pesticides.
SO3(g) + SCl2(l) OSCl2(l) + SO2(g)

The thermodynamic data listed below are for 298 K. Determine the temperature at which Keq = 1.0 10^15 for the reaction.

delta Hf(kJ/mol): .....S, J/mol*K
SCl2(l): -50.......150
OSCl2(l): -250 ....120

Answer 1

Working backwards, you know Keq (presumably you mean Kp, not Kc).

Use

1) deltaG0 = - RT ln Kp (care! You want ln, not log)

2) deltaG0 = deltaH0 - T deltaS

3) To get deltas, use {products} - {reactants} (you will need data for all the products and reactants; you only list two of them)

Combine (1) and (2) to give

deltaH0 - T deltaS = - RT ln Kp

Shove in the numbers you got in (3) and you have a linear equation in T, which is what you want.

Take care that your units are consistent. You will need to use J/mol for deltaH0 (not kJ, a very common mistake) and R in J K-1 mol-1

We have assumed that deltaH0 and deltaS do not themselves change with temperature. This is not strictly true, but near enough for most purposes.

Some sticklers won't let you call it deltaG0 except at 298 K. If one of those is going to be looking at your answer, make sure you use whatever notation keeps them happy.