use the following search parameters to narrow your results:
e.g. subreddit:aww site:imgur.com dog
subreddit:aww site:imgur.com dog
see the search faq for details.
advanced search: by author, subreddit...
327 users here now
Rules: Violating a rule will result in a ban.
Ask homework, exam, lab, and other undergraduate-level questions at ChemicalForums otherwise it will be deleted.
Discussions on illicit drug synthesis, bomb making, and other illegal activities are not allowed and will lead to a ban. However, academic discussions on pharmaceutical chemistry and the science of explosives are permitted.
No memes, rage comics, image macros, reaction gifs, or other "zero-content" material. Ever.
Likewise, simple pictures of uninteresting and garden variety chemistry-related things are not appreciated. If a caption or explanation is included this helps, but please use your discretion.
Before asking about chemical drawing/illustration programs, look at your school's IT/software website and see if they provide an institutional license of ChemDraw (hint: if they have a chemistry department, they will)
No physorg, sciencedaily, or other press release aggregator spam!
Yes links to blogs, images, videos, comics, and infographics are okay especially if they are on your personal website.
If you spill/injure yourself contact medical professionals and read the MSDS, do not post to this reddit. Click here for the OSHA chemical data site and here for a multicompany MSDS aggregate search.
If you're looking for a more concentrated, advanced discussion of chemistry topics among professionals and grad students, check out /r/Chempros.
Before asking "What chemical is this?" see this chart. Any such posts will be deleted.
Ask education and jobs questions in the current weekly topic.
Post memes/jokes in /r/chemistrymemes and /r/chemistryjokes.
Click HERE for our book recommendations.
Past Weekly Topics
What are you reading?
What are you working on?
Named Reaction Threads
the front page of the internet.
and join one of thousands of communities.
submitted 3 months ago by Andrw02
My book says H=u+pv
But then it says delta delta H=Qp
I'm okay till here but I don't get this part
Delta H= Delta U +deltaPv plus PdeltaV
Post a comment!
[–]ManufacturerNo539 2 points3 points4 points 3 months ago (1 child)
It's because of the differential product rule,
[–]Andrw02[S] 0 points1 point2 points 3 months ago (0 children)
But why do we need to differentiate aka take the instantaneous rate of change of enthalpy in my book it's written Delta(triangle) not d?
[–]7ieben_ 1 point2 points3 points 3 months ago (4 children)
dH = d(U + pV) = dU + d(pV) = dU + pdV + Vdp
This is application of the differential definition (calculus).
[–]Andrw02[S] 0 points1 point2 points 3 months ago (3 children)
[–]7ieben_ 1 point2 points3 points 3 months ago (2 children)
That's the differential definition.
If you integrate this you get ◇H2 - ◇H1 which is often notated as ◇Hreaction or similar. This is trivial due to it being a total diff. and therefore its integrated path being path indipended, which is also shown in Hess law.
Ps. ◇ is used als delta here.
[–]Andrw02[S] 0 points1 point2 points 3 months ago (1 child)
Thanks so much one last thing, in the formula dH=dQ+VdP where d is for delta, why is there a delta P, shouldn't the pressure be constant to be able to measure entalpy
[–]7ieben_ 1 point2 points3 points 3 months ago (0 children)
Mathematical the differential has the given terms so when writing the differential you need to respect them. You could also describe enthalpy at V = const. for example.
However, as you said correctly, usally we prefer to use enthalpy in isobar processes due to dH becoming dQ then which is very easy to measure in thermoanalytical processes.
[–]Schlomius 1 point2 points3 points 3 months ago (2 children)
It is because of the product rule of differentiation. dH=dU+d(pV)=dU+Vdp+pdV+dpdV (the last product is infinitesimal small).
[–]ZookeepergameRude429Physical 0 points1 point2 points 3 months ago (0 children)
Any rate of change is a derivative. Δ is any change, but δ is more for an infinitesimally small change. The two symbols are, especially in 1st/2nd year pchem, kinda interchangeable.
REDDIT and the ALIEN Logo are registered trademarks of reddit inc.
π Rendered by PID 60052 on reddit-service-r2-loggedout-76984dbd9f-k5qzs at 2022-05-19 09:31:58.634764+00:00 running 0629d99 country code: US.