# Need help w/ a Chem prob.

Discussion in 'Pre-Medical - MD' started by WorkOnIt, Nov 26, 2002.

1. ### WorkOnIt Junior Member 7+ Year Member

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For the reaction

S + O2-----> SO2 DeltaH = -296 kj/mol

how much heat is evolved when 275 g sulfur is burned in excess O2

2. ### mws99 Senior Member 7+ Year Member

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Use the atomic weight of sulfur and convert the amount you have (275 g) to moles. Then multiply the number of moles by the delta H. That's it. Ignore the O2 because it is excess.

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Thanks yo.

4. ### WorkOnIt Junior Member 7+ Year Member

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can anyone tell me why the answer in the book is positive, but when u calulate it urself its negative

when i did the math it comes out to -2536, when u multiply 8.57 mol S and -296 kj/mol

in the book the answer is 2.54 x 10 to the 3rd power.

it cant be a typo b/c there's another similar question and sign ,when i calulate, doesnt come out right

5. ### 14931

heat evolved is already negative so i think the book is just saying that's the heat evolved , get?

its like they are not repeating themselves, anyway thats what i think i might be wrong.

6. ### souljah1 Attending 10+ Year Member

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you can't evolve negative heat. the negative sign implies that it is exothermic and b/c of this, you know that the reaction gives off heat. it's been 5 years or so, but i think that i'm right on this one.

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makes sense

8. ### 14931

which one, mine or souljah's?

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