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

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How much energy is required to make an ion?

So say that I have a normal hydrogen atom (not an isotope, just regular normal hydrogen atom) and I want to make it into an ion $\text{H}^+$. Since to make an ion of that formula I need to take away ...
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40 views

How big is the gauche interaction of methyl with phenyl in a disubstituted cyclohexane?

I'd like to compare the equatorial 1-Methyl-2-phenyl-cyclohexane conformation of with axial conformation of 1-Methyl-3-chloro-cyclohexane conformation. In which molecule there is less steric ...
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1answer
57 views

Why does attraction always cause release of energy making the system more stable?

Suppose $\ce{Na^+}$ and $\ce{Cl^-}$ form an ionic bond. In doing so they will come closer by attraction. Now as they come closer their speed will increase and hence the kinetic energy increases. So ...
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26 views

what kind of energy is released when a chemical bond breaks [duplicate]

Basically the energy stored in a chemical bond is potential energy of the electrons. So basically we have two rotating negatively charged spheres (electrons) that are naturally repulsive between them, ...
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enthalpy change of a reaction

I had the following problem: Given the information: $$\begin{align}&\Delta H_\mathrm{c} (\mathrm{graphite}) &&=-394\ \mathrm{kJ\ mol}^{-1}\\ &\Delta H_\mathrm{f} (\ce{H2O}) ...
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1answer
88 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 ...
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1answer
35 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.
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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
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2answers
181 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 ...
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1answer
74 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 ...
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40 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 ...
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45 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 ...
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1answer
39 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 ...
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2answers
230 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 ...
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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 ...
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1answer
74 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)?
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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: ...
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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 ...
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1answer
148 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 ...
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2answers
208 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? ...
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1answer
78 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 $D_q$ ...
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62 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} \, \, ...
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2answers
172 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, ...
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1answer
38 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 ...
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1answer
76 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: ...
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1answer
104 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 ...
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1answer
88 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 ...
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100 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?
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422 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.
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56 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 ...
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1answer
82 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..
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35 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 ...
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1answer
37 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}\ ...
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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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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?
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1answer
78 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 ...
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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 ...
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1answer
109 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 ...
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2answers
89 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 ...
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1answer
87 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 ...
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28 views

Why does the electron affinity increase in the 15th group

Why does the electron affinity increase by going down through the 15th group?
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152 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 ...
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0answers
29 views

What is the heat of dissolution of sodium acetate trihydate?

Is the reaction endothermic since its crystallization is exothermic?
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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 ...
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1answer
104 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 ...
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70 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 ...
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1answer
88 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 ...
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1answer
43 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 ...
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119 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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2answers
46 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?