How do I do...?

Question

Consider:
S + O2 --> SO2 delta H = -296 kj/mol

How much heat is evolved, when 275 g sulfur is burned in excess O2?

Answer 1

For each mole of sulfur burned you will get -296 kj so, all you have to do is determine how many moles of sulfur you have. Sulfur weighs 32g/mole so just take the 275g divide by 32 to get moles of sulfur, then multiply by the -296kj/mol to get total heat evolved.

Answer 2

If this eqtn is for 1 mole of sulfur (32 grams), you just do the following calc:
-296 kj/mol * (275 g/32 g/mole)

Answer 3

First convert grams of S to moles.

275g* (1mole S/ 32.065g). The grams will cancel out leaving 8.57611 moles of S reacting.

Since 1 mole of S reacting will produce -279kj, then 8.57611 will produce 279kj x 8.75611 = -2392.8 kj