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What happens to a molecule while it is reacting?

Well, a lot of things happen to the reactants. Some bonds stretch (and maybe eventually break), the others shrink, and your molecules morph into different molecules, which are the products. (source) ...
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28 votes
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What really happens atomically in an explosion?

The combustion of alkanes like butane is fearsomely complicated involving dozens of transient compounds and hundreds of different reaction. If you have a few spare hours there is a dissertation that ...
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20 votes
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Why six C atoms are usually seen in cyclic compounds?

It is all about minimizing the energy of a molecule. In the case of carbon, the only molecule that adopts a perfect hexagonal geometry in its ground state is benzene (and its derivatives that possess ...
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20 votes
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Is activation energy temperature-independent?

There is a simple (some might say simplistic) way to get an intuition about this and it involves thinking at the molecular or atomic level rather than about the bulk properties of the reaction (the ...
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20 votes
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Can carbon dioxide be reduced to carbon monoxide and oxygen to produce energy?

Unfortunately, the question as stated is thermodynamically impossible. Let's look at the proposed reaction: $$\ce{CO2(g) -> CO(g) + O(g)}$$ This reaction is simply a bond dissociation (specifically,...
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20 votes

Where does the energy from combustion come from?

Better is to say "Energy released by forming bonds of combustion products is bigger than energy needed to break bonds of combustion reactants.". Particularly breaking $\ce{C-C}$, $\ce{C-H}$ ...
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19 votes
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If aliens lived in a hydrogen (or any flammable gas) based atmosphere, would they perceive oxygen to be flammable?

Absolutely yes. Lighting a torch in such an environment would simply be the reverse physical process (and same chemical process) of what is done in our oxygen-containing atmosphere. In the chamber ...
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17 votes
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Is iron the most stable element in the periodic table?

Yes, $^{56}\ce{Fe}$ has the most stable nucleus, and $\ce{He}$ is the most chemically inert element. These are different and unrelated qualities, pretty much like physical fitness and intelligence in ...
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17 votes

Why is it that protons and electrons undergo the same amount of deflection in an electric field if they have the same energy?

Now that's a mildly non-trivial observation. Why would they be equal, really? Let's say a particle with mass $m$, charge $q$, and initial velocity $v$ enters an area of length $L$ where an electric ...
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16 votes

Why do electrons jump back after absorbing energy and moving to a higher energy level?

This is a very fundamental question and for really understanding the "why" some advanced physics is involved. I will describe the process rather superficially. As you might know, the level ...
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15 votes
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Is Bond Formation "Strictly" Exothermic?

Bond formation is alway strictly exothermic in the sense of the change of enthalpy. exothermic reaction A reaction for which the overall standard enthalpy change $\Delta H^\circ$ is negative. A ...
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14 votes
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Which has higher lattice energy: MgO or LiF?

$\ce {MgO}$ ($\approx 3800$ $\pu{kJ mol^{-1}}$) has higher lattice energy than $\ce {LiF}$ ($\approx 1045$ $\pu{kJ mol^{-1}}$) mainly because of the greater charge on $\ce{Mg^2^{+}}$ ion and $\ce {O^{...
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14 votes
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Can Rydberg constant be in joules?

Authors may be sloppy about notation in this matter. I recommend considering $R_\ce{H} \approx \pu{10973 cm-1}$ and $Ry \approx \pu{2.18e-18 J}$, noting $Ry = hc \cdot R_\ce{H}$. Units of wavenumbers $...
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13 votes
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ATP break down and energy release?

A bond is formed between the oxygen of water and the phosphorus of the gamma-phosphate. Here is a good link. Bonds are both broken and made in chemical reactions but many biology teachers and ...
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13 votes
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Reason for inability to find the absolute value of internal energy

In order to answer this question, one needs to define what the absolute energy of a system is. Energy can be trapped in a system in ways not yet discovered or fully understood. Think of the energy ...
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13 votes
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Wouldn't radiolabelled phosphorus in DNA break it apart as it disintegrates?

Of course it would break, just like you said; also, a high-energy $\beta$ particle would kill quite a lot of bystander molecules. Also, if not for other reason, the resulting molecule would no longer ...
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12 votes

What really happens atomically in an explosion?

The butane and oxygen in the room are in a metastable state. An example energy diagram of a metastable state is shown in the image below. Before throwing in the cigarette, the butane and oxygen ...
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12 votes
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Significance of single point energy when calculating interaction energies

Single point energy arises in the framework of the Born–Oppenheimer approximation and corresponds to just one point on the potential energy surface. Physically it is the total energy of the molecular ...
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12 votes

Is the Gibbs standard free energy always constant?

In short, no, the standard Gibbs free energy change is not constant; it is a function of temperature. The same is true for practically all other standard-state quantities. This gets a little ...
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Why is the Gibbs free energy for phase changes zero at constant temperature and pressure?

The initial and final thermodynamic equilibrium states of your system are as follows: State 1: $\pu{1kg}$ liquid water at $\pu{0 ^\circ C}$ and $\pu{1 atm}$ State 2: $\pu{1 kg}$ water ice at $\pu{...
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12 votes
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Does the potential energy increase when temperature is raised?

Yes, potential energy increases with increasing temperature for at least the following three reasons: At a higher temperature, more atoms/molecules are in excited electronic states. Higher ...
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11 votes

Is iron the most stable element in the periodic table?

No, nickel-62 is the most stable on a binding energy per nucleon basis. Fe-58 is second and Fe-56 is third. See Fewell, M. P., "The Atomic Nuclide with the Highest Mean Binding Energy", Am. J. Phys....
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11 votes
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kJ per mole or kJ per 2 moles?

the whole reaction, i.e. for 2 moles of the product? This is your mistake. The balanced equation $\ce{2H2 + O2 -> 2H2O}$ does not mean that 2 moles of the product are being formed. The numbers, ...
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11 votes

Why is oxygen so special?

Dioxygen, $\ce{O2}$ is a very special molecule. A good majority of organisms on earth use dioxygen to breathe and survive. Oxygen is also the second most abundant element in the sky, as well as the ...
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10 votes
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Why is oxygen so special?

Your question is quite broad, so I will tackle it in parts. Element abundance there is nothing as familiar to mankind (in terms of the frequency in their occurrence) as the reactions involving ...
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10 votes

Define, (actually define) the "stability" and "energy" of a compound

As a chemist, I would agree that textbooks are not clear about the term stability and energy. It is not your fault and undergraduate organic chemistry books make the situation worse. I cannot recall ...
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10 votes
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Why is the principal energy of an electron lower for excited electrons in a higher energy state?

Notice that when $n=1$, we have, $$ E=-E_0=-13.6~\mathrm{eV} $$ which is the negative of the energy required to remove an electron from the ground state of a hydrogen atom. If we increase $n$ to say $...
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10 votes

Can Rydberg constant be in joules?

Rydberg constant $R_∞$ is usually given in reciprocal length units historically and because it's determined from hydrogen and deuterium transition frequencies [1]. Current value (in $\pu{m-1}$) is ...
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10 votes

Does energy come from fuel or oxygen? (surprise?)

[OP:] It is usually said that fuel contains energy and that oxygen only enables the release of energy in the sense like enzymes enable reactions. An enzyme is a catalyst, so it does not change the ...
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10 votes
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Pressure exerted by a particle of ideal gas

Here's your confusion: You need to consider two different things: The momentum transfer per particle per collision. There, since we assume an instantaneous collision, it doesn't make sense to try to ...
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