18. Introduction to Chemical Equilibrium

MIT 5.111 Principles of Chemical Science, Fall 2014
Instructor: Catherine Drennan

Reactions reach chemical equilibrium when the rate of the forward reaction equals the rate of the reverse reaction. In this lecture, we discuss the nature of chemical equilibrium and of the chemical equilibrium constant. We start to consider how external factors can “push” the equilibrium in one direction or the other. Physicist and Chemist Nozomi Ando provides an example of why chemical equilibrium is important in living organisms.

License: Creative Commons BY-NC-SA

[AnneCalie]

I really admire her commitment to her shirts!

[qunt]

I wish I was allowed to eat chinese food during lectures

[aditijuneja]

at 31:07 x has 2 solutions : 0.381 bar and 0.655 bar, why is 0.655 bar not discussed?
partial pressure for N2O would be -0.310 bar (if x=0.655 bar), what does that mean?

[Zenlollipop]

I don't suppose many people are still following this course now, but in case anyone is reading this and doing the problem sets on the ocw website: the solutions posted for the problem set for Lecture 18 are either incorrect or misleading. In the decomposition of phosgene question, the question provides an equilibrium constant as K, implying you might have to calculate the partial pressures to solve the problem, but the solution just uses that K value as Kc, the equilibrium constant expressed in terms of molar concentrations. In equations with a change in the total number of moles from products to reactants, these two constants are not equal. So at the very least, keep in mind that the constant provided might be Kc.

In the second question on the decomposition of nitrosyl bromide, the same K =/= Kc issue persists. But the new issue is that nitric oxide is specified as being in the solid phase for some reason (I'm not sure this is possible because the boiling point of NOBr is higher than for NO). Presumably it is a typo, but if it is meant to be treated as a solid just as a mathematical exercise, its activity should be 1, not [NO]. The solution provided is correct only if the K provided is used as Kc, and NO is considered to be in the gas phase.

[irod]

The statement at 32:35 in incorrect. K>1 doesn't necessarily mean more products. Try to plug into this formula K=1.1 and see for yourself. (This is because we have twice more reactants than products here)

[joaonogueira]

great class I could understand everything

[garyraab]

The class assignment analogy, at the start of the class introduces misconceptions into the concept of chemical equilibrium. Learning is much better, in the longer term, to explain with a scientific model! The real world is complex. We go about trying to understand and explain the real world with models. Totally remove homework assignments and personification, and the real world of chemical equilibrium continues unaffected!

[chidipaul]

i love the work u are doing pls do video on chemical equilibrum

[Elias.]

14:10 Why would the units always cancel? Since c + d might not = a + b, like in the example at 23:00, wouldn't the units there be bar^-2?

[wittyusername]

42:07 that small company was Toast and it is now worth $30 billion at its peak and has $1 billion in annual revenue, wow

[BruinChang]

I think MIT students can do whatever they want to do because they are extremely intelligent.

[ayeshamuneer]

I have important question to ask if anyone can guide me that :.In Iupac nomenclature

"When numbering a cycloalkane with substituents, give the lowest number to the substituent that appears first in alphabetical order.But in some cases, the substituent with lowest alphabetical letter comes at higher locant while the substituent with higher alphabetical letter comes at lowest locant .so kindly explain what is the rule to follow here?

[kwangsikko]

Eating during class is allowed? it looks for me non

[Karim-nqbe]

Great teacher. "No unit, this is very exciting" -> I know it's really boring please hang in there T_T

[kallmekrissarchivetiktoks]

1.55 was that guy eating in the lecture hall? Is that even allowed during lectures??

[zack_]

13:30- Cameraman, good job! You found equations on her face by staring at her soo long! Or just attracted to her?

[johndeer]

Fractional reserve banking makes us all debt slaves!

[abcc]

How many paisas have seen this video 🤠 jaja