[HansonLoveFest]

Using the componds given below, calculate the standard enthalpy (kJ/mole) of a reaction that occurs at 298.15 K and produces 14.0g of SO3(g).


reactants: SO2(g) O2(g)

products: SO3(g)


This problem is confusing me. I'm reading the section of my text that explains it, but it's so brief, and doesn't really give me enough of an idea to figure out how to even do this. I have no idea what I'm supposed to do first.

Do I write some sort of balanced reaction equation?

Do I split all the reactants into elements (as per normal calculations of standard enthalpy)?

And then how am I supposed to incorporate the 14 grams of product?

I feel like I have bits of the main idea, but there's seriously no resource my school gave me to help. I'm left with 3 unhelpful pages in a textbook.

[HansonLoveFest]

The furthest I got was trying to write out S + 1.5 O2 -> SO3

The values of standard enthalpy of formation in the appendix on my text are 278.805 for S, 0 for O2, and -395.72 for SO3.

Then I got the molar mass of SO3 (80g), and since it's asking for a reaction where 14 grams of the product is formed, that's 17.5%, so I tried using that, but to no avail. I'm not even sure if I was on the right track, but now I got stuck here.

[LQ43]

Do I write some sort of balanced reaction equation?

Yes.  Recall what your reactants and products are.

In those textbook pages, do you see a reference to Hess' Law and the sum of products and reactants using the enthalpy of formation?

You're right you have pieces of the correct solution...

Once you determine the enthalpy of the reaction then this can be related to the mass of the product to make a conversion factor. The enthalpy to produce 14 grams of SO3 can then be calculated.