Questionasker

Hi there

As a Chemistry student I've never understood this simple idea and that's why I'm asking anyone to help knock some sense into me. So my problem is NOT how to calculate moles, my problem is understanding the difference between the moles that you calculate in a reaction, given the mass of the reactant or product and obviously calculating the relative atomic/molecular mass, and the moles that's given in a balanced reaction.  To make things a bit clearer, the calculated moles of a reaction is very small, small than zero in some cases followed by many other numbers before the first significant figure, but the moles presented in a balanced reaction are usually integers.

If anyone needs me to be more specific by all means ask and I will gladly provide an example as to what I'm stuck with.

I don’t get how Br- can’t be a radical since I believe the hydrogen bromide undergoes homolytic fission, like Halogen molecules in free radical addition. To me they both seem the same but with slightly different steps.

Hi there

im really struggling to get my head around the difference between electrophilic addiction and free radical addition. I know the steps on these two different reactions but I just don’t get how they can differ from each other. One of the reactants, for an electrophilic addition can be simple like hydrogen bromide, the bond breaks from the double,triple bond acting as a Bronsted lowery base and the bromide is left with an unpaired electron, which I believe should be known as a free radical, so then it will form a bond with one of the carbocations and produce a halogenoalkane, for example.
 

I really just can’t distinguish the  the two of them and I’d really love some help. 
 

thank you

Thanks for the incredibly informative response. I'm starting to understand the formula, however I have some questions that I gotta ask.

From the formula  (ΔU= Q+W) are you claiming that Q and W can be negative? Furthermore when "heat is generated" via work done or from the heat added to the system, surely the values of Q and W would be positive instead of negative right?

Observing the formula further, I don't understand why W can be a positive when it needs to derive energy from Q in order for work to be done.

ΔU=Q+W

Hi everyone

I'll keep this short and simple, for the formula for the first law of thermodynamics how come the formula can be either negative or positive? E.G ΔU= Q + W/ ΔU = Q - W

I understand, thank you for your advise.

😄

Ok, I'd like to sincerely apologize for wasting your time. I had the wrong idea of what would happen to the reaction between Ammonia and hydrochloric acid. I had a completely idiotic idea of what would happen. Thank you for trying to reason with my stupidity.

As for your criticisms, i'll be sure to be much more specific with my questions next time.

Once again, thank you.

Hi, sorry for the incredibly long reply.

Not quite. I was just, in general, curious about why hydrogen would abandon its shared electron with chlorine to share 2 lone pair electrons with ammonia.

Hi, I know the very basics of quantum physics and yet I need to ask this silly quesiton.

Can there be an alternative form of electricity than revolves around the movement of positrons? Have I just asked the most stupid question in this forum? If it's possible, will anything be different with the electricity? If it's not possible then is it still possible for electricity to exist without electrons?

Keep in mind that I can't stress how little I know of quantum physics, I only understand the very, very basic ideas and equations from it.

Thanks for the correction, but how can we know that different molecules can form hydrogen bonds with themselves?

Hi, sorry for the late reply.

Just by looking at what they are, keep in mind that i'm only going to predict the boiling points. I actually have never heard of 'Diethyl ether' and 'Acetic acid' I predict it will go:

* Diethyl ether

* Acetic acid

*Ethanol

* Ethane

With an alcohol, i believe, intermolecular forces will exist since O-H has both a slightly negative and positive charge. The electrons of the O-H are unevenly distributed since Oxygen has a higher electronegativity than hydrogen, therefore pulling the electron towards it. This will then cause a Dipole dipole effect when there are different charges at opposite end of the alcohol. However, this happens for a very short amount of time since electrons move incredibly fast. So due to the Van der waals effect, the alcohol will have a temporary dipole effect which means that it can bond to other molecules, but I can't imagine that it'll be strong. So going by what I mentioned, If it's correct, the hydrogen should be oscillating between neutral and having a slighy positive charge. This must mean that it can covalently bond the hydrocarbon, such as ethane, to another ethane molecule.

I think I have a broad understanding, so if atoms are electrostatically pulled together then it will mean that it would require more energy to break their bonds. This could apply to molecules too.

Thank you for your reply.

So, just to clarify, the lone pair of electrons would produce a 'larger' electrostatic force than a singular electron from the chlorine. This would therefore cause the hydrogen ion to interact to the lone pair of electrons. Is this right?

Also, how come a lone pair of electrons have a stronger repulsion than a pair of electrons that are provided by another atom and an atom that its going to covalently bond to?

Intermolecular forces is a force between many molecules, it's much weaker than intramolecular. Electrostatic interaction is caused by atoms/molecules that have are attracted to opposite charges. I know that electrostatic interaction is the cause of ions interacting with each other since they can have the same or opposite charge.

Please correct me if I'm wrong anywhere.

Kind of, it was in a presentation from my college. They provided a 'rough' definition of the reason why it increases, which I can't remember for the sakes of me, so I figured to ask the people here. So its not necessarily homework, but it's out of curiosity.

Hi, I'm curious to know why adding an O-H to the end of a molecule can, or will, increase the boiling point of the molecule. How can this happen? What goes on when an alcohol group is added?

Hi studiot, thank you for the +1.

I have a 'decent' understanding of what lone pair electrons are. They have the strongest rupulsion and therefore causes the structures of some molecules to be different E.G Tetrahedral shape. It's just I don't understand why the H⁺ decides to go to the lone pair electrons from the nitrogen. Why did it move? It had a full outer shell from both the chlorine electron and its own electron. To be more specific:

Why did the H⁺ move towards the nitrogen atom when it had a full outer shell with chlorine?

Hey, I was looking at the reaction between ammonia (NH₃) and hydrochloric acid (HCl). Apparently from the diagram I saw the hydrogen from HCl would get drawn towards the nitrogen, leaving an electron behind for the chlorine. Why does this happen? Do lone pair electrons have a larger electrostatic force?

P.S forgive me if I've i may of done something wrong, I'm new to this website.