r/AskChemistry

Ill quickly explain the experiment first:

My teacher took an open can with a small hole at the bottom, which was first sealed with a cork. He placed the can upside down, hole facing up, and on a block such that the box was angled and had contact to air on the big opening.

He then filled the can with hydrogen gas, took away the cork, and lit the hydrogen, which was now streaming out slowly, on fire.

It was sizzling on for a while with only a small flame at the top, but at some point, it exploded and threw the can into the air.

The teacher asked why we had to wait for an explosion, afterwards he answered by saying at the point of explosion the ideal ratio 2:1 for the reaction 2 H2 + O2 -> 2 H2O was reached, because he wanted to illustrate that reactions need concrete ratios of substances.

However, i doubt this explanation, because there doesnt seem to be a way for the flame reaching the inside because the hydrogen was constantly flowing out, and i assumed the density of hydrogen causes layer separation between air, not a mixture.

Could this have to do with the flow rate of the hydrogen or with the shape of the distribution of hydrogen in the can? Or is the teachers explanation correct?

I need 8 graduate credit hours for my stipend but this semester my university doesn’t offer any grad courses other than “Intro” to QChem and Advanced Organic Synthesis. I literally have to take QChem because if I don’t I won’t be eligible for a stipend.

I hate quantum chemistry. I “cheated” my way through it in undergrad (was a joke bc we had a zoom class, all hw and tests were open book and group work, and the prof gave us “Jedi master”, and “Jedi Knight”, etc. as grades). I never even learned spherical coordinates in calc iii bc I stopped showing up to classes due to depression. Now I’m forced to take this hellspawn of a class my first semester of grad school. I don’t even know how to do calculus if the variables aren’t written X, Y, Z like in math class.

But the worst part isn’t that I don’t know it. It’s that I’m mentally blocking myself from learning it. I don’t want to learn it. It’s not relevant to an organic chemist to normalize wavefunctions or use rigid rotor. Computational Chem is the only part of the class I’m excited about. I’m spiraling and it’s only my second day I’m afraid I made a terrible mistake and my life will be useless if I dropout of grad school

Is this just a shit the bed and now I have to face the consequences and lay in it

This question isn't based on anything specific - It's just a shower thought - But could the production date of a plastic or metal or any other material be reasonably estimated by the amount of CO2 in it? And how accurate would it be?

Hey guys,

I don’t have a lot of experience in chemistry so i thought this subreddit could help me. I hope i do get some valuable advice and understanding.

Recently my brother has been planning on starting a small business project to process waste eggshells specifically to obtain pure calcium carbonate (CaCO3).

To be honest, I'm kind of worried he might be risking his money on this. I was reading somewhere that limestone is already mined at a massive, cheap scale everywhere for calcium carbonate, so I'm not sure how this makes financial sense. Plus, the whole processing and chemical extraction part of it looks super tedious.

To try and help him out, I actually went ahead and spoke to a few local farms myself. But the catch is, they said they're only willing to supply the shells with all the inner membrane and materials completely intact they aren't going to clean or prep them at all.

Since I don't know much about chemistry or manufacturing, I wanted to ask you guys: Is this actually a practical idea to get pure CaCO3, or is he walking into a total headache? Any advice or warnings would be awesome before he drops cash on equipment.

Thanks!

3.Is acid rain still a concern? Can we drink it? Some splashed into my eyes why it seemed fine?

guys why is it called daydreaming instead of imaginating something

We have a methanolic extract that needs to be freeze dried. The issue is that we don't have our own freeze dryer and we will just be sending our sample to have a freeze drying service. Their condition is that it should not have alcohol content which I am already aware because it will cause damage to the equipment.

Is using rotary evaporator be enough to remove the methanol in our extract before freeze drying or should we resort to just using water to be safe? We are just students and we dont want to be paying for the damage if ever :/

if the peripheral atoms are all identical around a central atom without any lone pairs, would the bond angle remain same, regardless of the electronegativity of the peripheral atoms for a given steric number? For example, we know that SiH4 and SiF4 have the same tetrahedral geometry and 109.5° bond angle even though H and F are vastly different in electronegativity. Does this hold for all steric numbers though?

Hey

Looking for some help setting up a distillation process to maximize recovery. The current setup uses an Allihn condenser to distill out the product of interest. I was wondering if a switch to a short-path distillation head will increase product recovery as there will be less surface area to retain the product. I understand the distillation will be significantly slower.

Thanks

I have searched that to add methanol again on the powder but I am confused if there is a specific ratio of methanol to powdered extract that I must follow?

Doing a research for a work to my classroom, going by the kinectics definition of K, which I'll explain shortly justo to get my point.

Considering an reaction: aA + bB ⇌ cC + dD

we have that the rate of equation (in portuguese we call it reaction velocity) for the forwards and backwards direction is:

vf = kf [A]a [B]b and v^(b)=k^(b)[C]^(c)[D]^(d)

We can use this to build the equilibrium constant, K=CD/AB, which does not have any units.

Now here is my question, K doesnt have any units because we consider the activity of the species (and because by the gibbs energy the argument is inside a logarithm so it needs to be dimensioneless). But if we need to consider activitys in K, so it must be that the concentration in the rate equations must be activity instead, which bugs me out because if that's is true, for the units of the velocity to be mols/L.s the entire rate constant should be mols/L.s, which dont seems right to me. If someone could clarify this to me I would be really happy, thanks!!