Question

How can you determine the heat of transition of Srhombic to Smonoclinic from the following

data using Hess’s law?

i. Srhombic + O2...... > SO2 ΔH = -291.4 kj

ii. Smonoclinic + O2...... > SO2 ΔH = -295.4 kj​

Answer 1

Answer:

Use the standard reaction enthalpies given below to determine ΔH° for the following reaction:

2S(s) + 3O2(g) ---> 2SO3(g)

Given:

SO2(g) ---> S(s) + O2(g)ΔH° = +296.8 kJ2SO2(g) + O2(g) ---> 2SO3(g)ΔH° = −197.8 kJ

Solution:

1) The two data equations are modified:

S(s) + 2O2(g) ---> 2SO2(g)ΔH° = −593.6 kJ <--- flipped and mult. by 22SO2(g) + O2(g) ---> 2SO3(g)ΔH° = −197.8 kJ <--- no change

2) The 2SO2 will cancel out when the equations are added. Add the enthalpies for the answer:

−593.6 + (−197.8) = −791.4 kJ