Question

Using the standard heats of formation below, what is the heat of reaction when sulfur dioxide reacts with oxygen to form sulfur trioxide? 2SO2(g) + O2(g) → 2SO3(g) ∆Hf° SO2(g) = –298.8 kJ/mol ∆Hf° SO3(g) = –395.7 kJ/mol –193.8 kJ –201.9 kJ –492.6 kJ –694.5 kJ

Answer 1

To calculate the heat of reaction we need to subtract the summ of all reagent's formation heat from the summ of all product's formation heat.
For this example it will be:
2*Hf(SO3) - ( 2*Hf(SO2) + Hf(O2) ) =
2 * (-395.7) - ( 2 * (-298.8) + 1 * 0) =
-791.4 + 597.6 = - 193.8

Answer 2

-193.8 kJ is the heat of reaction

Step-by-step explanation:

`2SO-2(g) + O-2(g) \rightarrow 2SO_3(g)`

Standard heat of formation of
`SO_2=\Delta H_(f,SO_2)=-298.8 kJ/mol`

Standard heat of formation od
`O_2=\Delta H_(f,O_2)=0 kJ/mol`

Standard heat of formation of
`SO_3=\Delta H_(f,SO_3)=-395.7 kJ/mol`

The heat of reaction =∑(Heat formation of products )-∑( heat of fromation of reactants)

`\Delta H_(rxn)=(2 mol*(-395.7 kJ/mol))-(2 mol* (-298.8 kJ/mol)+1* 0 kJ/mol)=-193.8 kJ/mol`

-193.8 kJ/mol is the heat of reaction