What is the change in enthalpy when 4.00 mol of sulfur trioxide decomposes to sulfur dioxide and oxygen gas? 250 2(g) + o2(g) ® 250 31 g): d hº = 198 kj a. -396 kj b. 198 kj c.-198 kj d. 396 kj e. 792 kj

A. -396 kJ

Explanation:

The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements, with all substances in their standard states.

Reversing the reaction, changes the sign of

On multiplying the reaction by 2, enthalpy gets multiplied by 2:

Thus the enthalpy change for the reaction  is -396 kJ.