For questions relating to energy required for or produced by reactions, including questions of endothermicity/exothermicity, bond enthalpy, etc.

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4
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1answer
68 views

Cis-trans isomers internal energy

Whilst reading about stereochemistry, I came to know that the stability and melting point of cis isomers is lower than trans isomers. By searching on net I've found the reason behind that. But one ...
0
votes
1answer
33 views

What is the bond energy [closed]

$\ce{Cl2}$ bond energy given is as 244. 1/2 $\ce{Cl2}$ will still be 244 or 244/2? My teacher said it is still 244.
-1
votes
1answer
26 views

Energy required to electrolyze water [closed]

What voltage DC current would I need to electrolyze 1 liter of water in 1 hour using 1 gram $\ce{NaOH}$ for a electrolyte
5
votes
2answers
155 views

Stability of Resonance Structures

So I was "happily" doing organic chemistry homework when I came across this question: I decided to take a look through my textbook to see what I was missing. The rules to compare resonance ...
3
votes
1answer
73 views

How to distribute the Boltzmann energy to internal and external motion?

If we have an isolated pentane molecule at room temperature (RT) the Boltzmann energy $(E=k_\mathrm{B}T)$ is approxately $0.59\ \mathrm{kcal/mol} \overset{\wedge}{=} 207\ \mathrm{cm^{−1}}$. There is ...
3
votes
0answers
37 views

Difference between single point energy and dimerization energy

I am investigating potential energy surface characteristics of some monomeric interactions (electrostatic) e.g. $\ce{F-H}$...$\ce{F-H}$. I'm using dft/mp2(scs) to perform the necessary calculations ...
-4
votes
0answers
21 views

The energy of radioactive elements [duplicate]

I asked a similar question about $\ce{^{99m}Tc}$. What components are needed in finding the energy output of a radioactive isotope? In (kWh) An example is one kilogram of uranium 235 puts out around ...
8
votes
0answers
39 views

Disregarding negative externalities and other barriers, what are some fuels that have a higher power density than gasoline?

Gasoline’s power throughput per kg is $12\,200\:\mathrm{Wh/kg}$ (Wikipedia.org). Are there any other fuels that have a higher power output that are not considered viable solutions as they are ...
3
votes
1answer
35 views

kWh of radioactive elements database?

I recently been studying different radioactive elements. The most difficult part is find the output of these elements in the form of kWh. Is there a database or chart of these elements' output? And ...
5
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2answers
209 views

significance of single point energy

I am currently investigating about the interaction behavior of few atoms in certain conditions. So, is it possible to use the concept of single point energy to represent the atomic interaction ...
2
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0answers
24 views

Should I consider the quantity of each atom when estimating the relative lattice energies of two compounds?

In this video, at 1:30, the presenter remarks that the charge of $\mathrm{Na}$ is $1^{+}$ and that the charge of $\mathrm{Cl}$ is $1^{-}$. Then, at 2:00, he remarks that the charge of $\mathrm{Fe}$ is ...
-3
votes
1answer
72 views

Energy of photon [closed]

What is a photon and how is its energy directly proportional to frequency of light (please don't tell that it is because $E=h\nu$ relation)?
6
votes
1answer
47 views

What are B and n in this expression for charge repulsion?

In a study of the creation of ionic bonds of in this case $\ce{Na}^+$ and $\ce{Cl}^-$ into $\ce{NaCl}$, I have come across this equation for the overall energy of the system: ...
4
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0answers
32 views

Catalyzation in Carbonic Acid

I understand the basics of carbonic acid + 1 kcal breaking down into water and carbon dioxide. However, my professor wants me to draw an energy map showing the catalyst in human blood reducing the ...
5
votes
1answer
135 views

Periodically oscillating chemical reactions?

I've seen before chemistry demonstrations where solutions are mixed with one another and subsequently where the resulting product goes through periodic color changes: for example blue to orange and ...
3
votes
2answers
145 views

Energy of photons emitted by de-excitation of electrons

When an electron of an atom returns from an excited state to the ground state, it emits energy in the form of a photon. How does the change in energy level compare to the energy of the emitted photon? ...
6
votes
1answer
60 views

In Crystal Field Theory what does Δo=10Dq mean?

While studying the Crystal Field Theory I was told $D_q$ is a unit, related to the unit $\Delta_{\mathrm{O}}$ by the relation $\Delta_{\mathrm{O}} = 10 D_q$. But aren't $\Delta_{\mathrm{O}}$ and $D_q$ ...
2
votes
0answers
56 views

Dissociation Energy for CO2 per molecule

I'm trying to calculate the energy required to dissociate a single $\ce{CO2}$ molecule into its respective elements, and I'm given that it takes $ 373.6 \times 10^{3} \, \, ...
8
votes
2answers
159 views

Rotational degrees of freedom (3N-5 and 3N-6)

In spectroscopy we described the electric energy with the approximative separability of internal motions as: \begin{equation} E=E_e+E_v+E_r+E_{ns} \end{equation} (energies: electronic, vibratory, ...
4
votes
1answer
37 views

Why is it that less useful energy can be extracted in explosive reactions?

If you extract energy from a substrate (e.g. glucose) step-wise, a lot more free energy is released that can be used. However, if you were to do this in one single step, very little useful energy ...
4
votes
1answer
67 views

Burning a diamond produces how much energy?

How much energy is produced by burning a 1 ct. diamond? I'm trying to figure out how much energy to build the diamonds in a biological process. See here: ...
4
votes
1answer
102 views

Increase in Potential Energy When Bonds Are Broken

Why is it that the potential energy of a system increases when its bonds are broken? (I.e. when a solid turns into a liquid.) I thought the potential energy of the system was mostly contained in these ...
2
votes
1answer
78 views

Endothermic Conversion of Liquid to Gas

When a liquid (in my case I used butane) under high pressure is released into the air, it becomes gaseous, and the container seems to get colder. Why is it that turning a liquid to a gas requires ...
7
votes
2answers
97 views

Why is energy released as electrons move?

Why is it that energy is released from electrons when they move from one atom to a more electronegative one?
3
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2answers
378 views

Is the 'n' in Delta G = -nFE, ever negative?

Is it possible for 'n' to ever be negative? Trying to figure out where I went wrong on some thing and want to rule that out.
5
votes
0answers
54 views

Does liquids that emit light when vibrated exist?

I am looking for a liquid that illuminates when vibrations are added. It does not have to be strictly chemical, it might as well be something else as well. Maybe a crystal in powder form mixed with ...
1
vote
1answer
59 views

Molar heat of fusion of ice?

The molar heat of fusion of ice is 6.01 kJ/mol. Can you explain what this means? What I think it means is that it requires 6.01 kJ to melt a mole of ice. I'm not positive though..
2
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0answers
33 views

In entropy change of surroundings, what is T?

This question is simpler than the previous one about intuition of entropy; I just need to know whether the $T$ term in $dS_{Surr} = \frac{-dH}{T}$ refers to the temperature of the surroundings or the ...
1
vote
1answer
36 views

Using enthalpies of formation and combustion to find formation enthalpy of Acetylene (Hess' Law)

I understand this is a simple question (I’m in high school), but for some reason the numbers just are not working for me. Given: $$\Delta H^\circ_\text{c} = -1301\ \mathrm{kJ}\ \text{for}\ ...
2
votes
0answers
28 views

Is Polymorphism accompanied with an energy change?

Differential Scanning Colorimetry (DSC) is a technique used to identify Polymorphism by revealing two melting points of a pure crystalline structure. DSC shows a peak associated with the formation ...
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0answers
31 views

Ionisation Energy (removal of electron) [closed]

My question is: Relate the ease of removal of an electron to the charge on the most stable ion formed by the element?
5
votes
1answer
70 views

Do core electrons in bulk material have discrete energy levels or continuous energy band?

The energy band of valence electrons gets smaller and smaller when the lattice (bulk) atoms are more and more separated from each other, until discrete energy levels are formed, due to the isolation ...
-3
votes
1answer
51 views

Calculating Energy Change of Acetic acid [closed]

A 10.0 g sample of pure acetic acid (CH3COOH) is completely burned. The heat released from the combustion is used to warm 2.00 L of water from 22.3 ℃ to 39.6 ℃. Assuming no heat was lost to the ...
1
vote
1answer
108 views

Relative energies between reactants and products

I've been asked to draw a relative energy sketch of the reactants and the two products. The reaction being examined was adding copper acetate monohydrate to glycine in two different fashions to create ...
2
votes
2answers
81 views

Are all naturally occuring reactions exothermic?

If a reaction is endothermic, then the reaction must take energy from the environment to occur (as far as I know), and if this is the case, then to me the reaction seems energetically unfavorable, as ...
0
votes
1answer
77 views

How much water evaporates In a vacuum before freezing?

I placed a container with 1000 grams (1 kg) of water at room temperature (20 degrees celsius) Inside a vacuum at 0.03 atm pressure. The water boiled for a few seconds then froze solid. I need to ...
0
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0answers
26 views

Why does the electron affinity increase in the 15th group

Why does the electron affinity increase by going down through the 15th group?
6
votes
2answers
131 views

Is most of the weight you lose actually released as carbon dioxide when you exhale?

I've heard that most of the weight you "lose" is actually carbon dioxide released when you exhale. In percent its much more than what is released in pure heat energy and feces. Does anyone have ...
0
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0answers
26 views

What is the heat of dissolution of sodium acetate trihydate?

Is the reaction endothermic since its crystallization is exothermic?
1
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1answer
19 views

Ideal gasses reaction under const temp and pressure

Conceptual problem: let $A + 2B \rightarrow C + 2D$ be a reaction under constant pressure (P) and temp (T), that goes all the way towards the products. A,B,C,D are ideal gases. let $\Delta H$ be the ...
4
votes
1answer
95 views

Safe yet strong exothermic reaction?

I'm studying chemical engineering at uni (Belgium), and this year (my 2nd) we have to develop and build a stirling engine. It has to be powered by a relatively safe exothermic reaction (not dangerous ...
2
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0answers
62 views

Why does the definition of ionisation energy only include gaseous atoms?

I know that in physics there is thermionic emission and the photoelectric effect. These are both method of removing electrons. I think these affects are only for metals due to their de-localized ...
3
votes
1answer
83 views

Can a reaction with positive Gibbs free energy change ever occur?

If you have an endothermic reaction with a negative entropy change, is it still possible to induce the reaction in some way despite the fact that the Gibbs free energy change is positive or all ...
1
vote
1answer
42 views

Entropy - Negligible?

In electrochemistry, the Nernst equation tells us the cell potential for non-standard conditions. I read that the factor $\frac{-RT}{nF}\ln{Q}$ accounts for difference in cell potential due to ...
1
vote
0answers
108 views

What is Barrier-less reaction in Quantum Chemistry?

After finding a reaction "Transitional State " by GAMESS and finding Hessian Eigenvalues, my project instructor said: " seems your imaginary frequency ( negative eigenvalue ) is not that big ( it is ...
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vote
2answers
44 views

The relationship between energy and air pressure?

When boiling water at room temperature, what is the relationship energy has with the air pressure that is making the water boil cold instead of hot?
1
vote
2answers
74 views

Gibbs free energy or reaction enthalphy

If I conduct a reaction say, $$\ce{CaO(s) + H2O(l) \rightarrow Ca(OH)2 (aq)}$$ let us say , I want to measure the energy generated from the reaction.Will this energy I calculate equal the change in ...
6
votes
1answer
383 views

Does the “Bat Gen” claim to produce more energy that it uses?

These links claim that inventor Arturo Solis Herrera has created an "everlasting battery". http://www.mexiconewsnetwork.com/news/bat-gen/ http://www.faqs.org/patents/app/20090134007#ixzz10Sh9iLQM ...
2
votes
1answer
151 views

What tools can be used to estimate binding energies?

I want to estimate the binding energies of various molecules. What are the analytical and numerical tools I can use for this purpose? In particular I'm interested in bonding energies of dyes to ...
3
votes
1answer
143 views

Gibbs Free Energy : What is it trying to say actually?

"Gibbs Energy is the useful work that can be extracted from the heat of a rxn or a thermodynamic process." I understand how it predicts the feasibility of a chemical rxn, considering the Entropy ...