# helppppppppppp! gc question

Discussion in 'DAT Discussions' started by JustwantDDS, Aug 8, 2011.

1. ### JustwantDDS DrAMG 7+ Year Member

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ok so the part i boxed off as red.....when u decrease P of O2 ...doesnt it shift to the side with more moles?
and it says favors reactants........... which is left but thats not the answer
the answer is decrease P of everything..............

2. ### PooyaH 2+ Year Member

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I think the explanation under the question, says it best! lol But when you decrease the pressure of a gas, it's essentially same thing as saying decreasing the amount of that gas, so when you decrease the amount of O2, it's gonna make the rxn **** to the right to make more O2. But when you decrease the overall pressure, the volume is being increased, so the rxn will shift to the side that has more moles of gas! In this case, you have 1 mole of H2O2 and 1/2 mole of O2, so the rxn would shift to the left where there is more moles of gas.

3. OP

### JustwantDDS DrAMG 7+ Year Member

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ohhh so individually reducing pressures is like taking away /reducing..........
but overall P decrease will be shift towards the side w most moles... right?!

merci!

4. ### PooyaH 2+ Year Member

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Yezzur. I always relate it to volume since it's a bit easier to follow. Whenever the question says P decrease or increases, I think of it as Volume increases and decreases respectively. (since P and V are inversely related). And when volume decreases, rxn shifts to the side with less moles of gas, and when volume increases, rxn shifts to the side with more moles of gas. Just a bit easier to follow than pressure vs. moles of gas IMO.

khahesh!

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