Question

Find ΔHrxn for the following reaction: 3S(s,rhombic)+2O3(g)→3SO2(g) Use the following reactions with known ΔH values: S(s,rhombic)+O2(g)3O2(g)→→SO2(g)2O3(g)ΔH=−296.8 kJΔH=+285.4 kJ Express the energy to one decimal place and include the appropriate units.

Answer 1

Given reactions,

S(s) + O2 (g) -----> SO2 (g) ; dH = -296.8 kJ -------------1st eq

3 O2 (g) -----> 2O3 (g) ; dH = +285.4 kJ---------------2nd eq

Reverse the second reaction,

2 O3 (g) ------> 3 O2 (g) ; dH = -285.4 kJ -----------3rd eq

Multiply eqaution 1 with factor 3

3 S (s) + 3 O2 (g) -------> 3 SO2 (g) ; dH = -296.8 * 3 -----------4th eq

adding 3rd and 4th equations,

3 S (s) + 2 O3 (g) ---------> 3SO2 (g) ; dH = -296.8*3 +(-285.4)

                                                        dH rxn = -1175.8 kJ