constant pressure


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Clement Ng
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constant pressure

Postby Clement Ng » Thu Jan 25, 2018 3:11 pm

I understand that at constant pressure, q= delta H, but do you use enthalpy of the reaction or enthalpy of formation?

Christine Wastila 1H
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Re: constant pressure

Postby Christine Wastila 1H » Thu Jan 25, 2018 3:17 pm

That statement refers to the enthalpy of a reaction.

Justin Chang 2K
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Re: constant pressure

Postby Justin Chang 2K » Thu Jan 25, 2018 4:04 pm

Yes. As long as you know the reaction is performed under constant pressure (if it's in an open beaker) then q=deltaH(rxn)

MSkye Goldwater 2K
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Re: constant pressure

Postby MSkye Goldwater 2K » Fri Jan 26, 2018 12:00 am

Would you have to take into account the number of moles of gas in relation to the balanced equation when solving for q ?

Matthew Lin 2C
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Re: constant pressure

Postby Matthew Lin 2C » Fri Jan 26, 2018 2:12 pm

MSkye Goldwater 2K wrote:Would you have to take into account the number of moles of gas in relation to the balanced equation when solving for q ?

Yes it depends on how many moles the question says are reacting. For example, if the question says to find q when 3 moles of C2H6 are reacting, but your balance equation has only 1 mole of C2H6 reacting, then you must multiply the delta H of the reaction by 3 to find q.

Emma Ward 2C
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Re: constant pressure

Postby Emma Ward 2C » Sat Jan 27, 2018 1:49 pm

as previously mentioned, it is important to note that the units for delta H are kj/mole. Therefore, when determining the enthalpy for a specific molecule or compound in a reaction, you need to take into account the stoichiometric coefficient to determine the enthalpy for that specific molecule or compound.


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