Questions tagged [energy]
For questions relating to the energy required for or produced by reactions, including questions of endothermicity/exothermicity, bond enthalpy, etc.
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Where can I find the released combustion energy in NASA CEA rocket problem?
I am using NASA CEA program for a study project.
I have read the CEA Nasa user's manual over and over, yet I haven't found an answer to my question which is :
where can I found in the output of NASA ...
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Is heat a form of energy or is it just a transport of energy, not energy itself?
In every textbook I read, it says that heat is a form/type of energy... but in lecture, my professor said, that there is no such energy as heat and that heat is just a method by which we can transport ...
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How can reversible reactions be exothermic or endothermic?
So this may be a dumb question, but because the forward reaction of a reversible reaction releases the sane amount of energy as the backwards reaction absorbs (because the bonds that are formed from ...
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Arrhenius Equation : Interpretation
Consider the relation:
$$E_{Activation}=E_{Threshold} - E_{Avg}$$
Here the $E_{Avg}$ refers to the Potential Energy of the reactants. Now in order of meet $E_{Threshold}$ , the molecules must have ...
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Arrhenius equation - Proper Interpretation of Activation Energy term
Consider the normal form of Arrhenius Equation:$$k=Ae^{-\frac {E_a}{RT}}$$
The term, $e^{-\frac {E_a}{RT}}$, is interpreted as the fraction of molecules having energy greater than Activation Energy.
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Why do internal energy/heat and enthalphy differ? What is the physical significance of the $PV$ term for enthalphy of an ideal gas? [duplicate]
Let it be noted that this is not a duplicate of this downvoted-to-hell question, simply because I hope to ask it better!
I've been reading a thermo textbook and I've got a simple question.
The ...
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I calculated internal energy at various temperatures and pressures. My results differ from someone else's. Is this OK?
I would like to make sure that my understanding of internal energy is correct. I'm not a thermodynamicist, so apologies in advance for what is probably a basic question.
I previously calculated ...
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Energy and impurities balance for adsorption with a fixed bed (with description)?
Do you have any suggestion where to look for a source of information about energy and impurities (component) balance for adsorption of mixture CO2/H2O in fixed bed?
I have looked into many articles /...
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Calculating Gibbs free energy for the reaction of burning methanol
Calculate $Δ_\mathrm{r}G^\circ$ for the following reaction:
$$\ce{2 CH3OH(l) + 3 O2(g) -> 2 CO2(g) + 4 H2O(l)}$$
using $Δ_\mathrm{r}H^\circ$ and $Δ_\mathrm{r}S^\circ$ at $\pu{298.13 K}$ $(\pu{25 °C}...
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Meaning of chemical energy [duplicate]
I am trying to understand the meaning of chemical energy.
I saw in my book that chemical energy is stored in the bonds of chemical compounds and when the bonds are untied the chemical energy increases....
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Change in temperature if salt is dissolved in water with different initial temperatures
I will mix a salt with room-temperature water and 8 degree Celsius water. Then I will compare the heat of solution with each other.
Does the initial temperature of the water affect how much the heat ...
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Efficiency of H production from FeOOH catalyst?
Research has recently found that FeOOH is 25 times better at hydrogen production than titanium dioxide.
Today, a new electrolysis plant delivers energy efficiency of around 80%. Is 25x the Honda-...
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Effect of intramolecular hydrogen bonding on the stability of a molecule
What will be the effects of intramolecular hydrogen bonding on the stability of a molecule? Will it increase or decrease the overall stability of a molecule? Or will it not have any impact on the ...
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What is the significance of the downward arrows in energy level diagrams in organic chemistry?
The following text is from Solomons, Fryhle and Snyder Organic Chemistry Third Edition, chapter 1 "The Basics: Bonding and Molecular Structure", page 13, topic 1.5 "Resonance Theory&...
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Is kinetic energy proportional to temperature for non-gases?
If the molecules in a sample of ice at $\pu{-15 °C}$ and $\pu{1 bar}$ all have their kinetic energy doubled, then what is the final phase?
The answer is gas, but I am not sure how to get this answer.
...
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Energy Levels of Molecular Orbitals formed by combination of Atomic Orbitals
In general when we talk about chemical bonding, we say that it is "nature's way to stabilize the systems" and the energy of the molecule formed by atoms will be lower than that of the individual atoms;...
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Combustion of carbon with hydrogen [closed]
Can coal (carbon) be "burned" in a hydrogen atmosphere? I know it would not match the definition of "combustion".
But is the reaction $$\ce{C +2H2 ->CH4}$$ exothermic?
(I'm fairly convinced this ...
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Ratio of total energy to kinetic energy in hydrogen atom when the reference is changed
If in the hydrogen atom potential energy at $\infty$ is chosen to be $\pu{13.6 eV},$ then what is the ratio of total energy and kinetic energy (with the sign) for the first Bohr orbit?
I think we don'...
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What is meaning of LAV2P basis set?
I am working on energy optimization of molecular structure using DFT with Schrödinger software and I found that job is running on LAV2P basis set. I want to know what is the meaning of this basis set ...
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Why is it easier to break a C-H bond of methane after another C-H bond has already been broken?
Bond energy explanations say the number given is often an average.
For instance, in methane, the $\ce{C-H}$ bond dissociation energy is the total energy required to remove all four hydrogens, ...
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Where does the energy of solar radiation hitting the atmosphere go?
I was reading about solar radiation, and there was a part that says that the atmosphere absorbs most of the radiation emitted by the sun. I wonder if when the atmosphere absorbs the energy, where does ...
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Why only two modes of energy exchange?
In the thermodynamics chapter of the 11th standard, I read something that I have a hard time believing to be true:
"There are two ways by which a system can interact or exchange energy with its ...
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Energy and time considerations in chemical reactions
I'm working on hydrothermal decomposition of organic matter at high temperature and pressure (400 bar). The reactions are too complex and numerous to model individually, but proceed in a similar ...
JHawkes
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Can you derive a formula for any internal energy of a gas as long as you know the degree of freedom?
I have the following formula that I derived from studying my textbook that generalizes to all ideal gases:
Monoatomic molecular gases ($\ce{He, Ne}$ etc.)
Degree of freedom: 3
$\ce \frac{3}{2}nRT = ...
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Could the net equations for burning hexene be used as a means of energy source?
$6\ce{CO_2} + 6\ce{H_2O}\xrightarrow{some\;catalyst}9\ce O_2 + \ce{C_6H_{12}}$
$\ce{C_6H_{12}} + 6\ce O_2\to 6\ce{CO_2} + 6\ce H_2$
$6\ce H_2 + 3\ce O_2\to 6\ce{H_2O}$
At one point, I had made a ...
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Energy in a Chemical Reaction
In a chemical reaction, is energy always either lost or gained by the reactants? As much as I am concerned, changes in energy can occur during the absorption of heat or the emission of light or heat (...
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Is the magnitude of ionisation enthalpy and ionisation energy is same?
In my textbook it is written that ionisation energy and ionisation enthalpy are two different quantities. ionisation energy is the amount of energy provided to extract an electron from the outermost ...
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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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If sigma bonds are stronger than pi bonds, why are the BDE's lower and the bonds longer?
If sigma bonds are stronger than pi bonds, why then do we say that the triple bonds which have 2 pi bonds are stronger than single bonds?
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Virial theorem confusion
Virial theorem says that $E_{t} = -\frac{E_{P}}{2}$ however this says that lets say for 2 gas molecules(Ne) the kinetic energy due to temperature a molecule of $Ne$ at 0K will have the same energy ...
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Relation between activation and threshold energies
Activation energy $E_\mathrm{a}$ and threshold energy $E_0$ appear to be equivalent quantities:
In particle physics, the threshold energy for production of a particle is the minimum kinetic energy a ...
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Why the second ionization energy of helium is greater than the first? [closed]
maybe because the first electron has a lower energy. Why does this happen?
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What exactly is the idea of gaining stability by the various chemical species?
When we consider the alkaline metals for example, we say that an atom of a metal like sodium gains stability by losing an electron, however this doesn't seem to be a very meaningful statement. Either ...
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Finding atomic number given energies of emitted photons
A hydrogen-like atom (atomic number $Z$) is in a higher excited state of quantum number $n$. This excited atom can make a transition to the first excited state by successively emitting two photons of ...
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Evidence for a chemical reaction
I know that the emission of light is evidence for a chemical reaction. However, are there any instances where emission of light can also be considered a physical reaction?
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derivation of enthalpy internal energy relationship [closed]
A question asks us to derive a relationship between the enthalpy change and the change in internal energy for a reaction.
Now, I know the relationship is:
$\Delta H = \Delta U + V \Delta p + p \Delta ...
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when would copper material have free electrons [closed]
If you imagine a wire of copper(note that I am not talking about electricity at all). Just only a wire of copper or copper metal or whatever full of copper atoms.
We know that each copper atom has 1 ...
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What makes a compound high or low energy and why does that relate to reactivity? [closed]
After reading about thermodynamic stability, it now makes sense to me how the enthalpy of a reaction relates to the thermodynamic stability of a compound.
However, when looking for a clear way to ...
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Why does a carbon double bond "break readily" but this is not so for other elements (nitrogen double and triple bonds are stronger)? [duplicate]
A level chemistry student here, fairly basic question. We always learnt (from GCSE bond enthalpies) that "Bigger bonds are stronger", so to speak; my teacher often quoted $\ce{N#N}$ as very ...
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Why electrons do not distribute evenly among the atoms in a molecule? [closed]
I was wondering why the state where electrons are evenly (or the closest to being evenly) distributed among the atoms in a molecule is not the lowest energy state? For example, in a water molecule it ...
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Why does Delta H change when the coefficients change in a reaction?
So I understand that if twice as much of the reactants are present, then twice as much energy is released. But isn’t the energy released per mole of reactant still the same? You are just scaling up ...
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How can I measure the energy contained within water vapor?
Let’s say I have a kilogram of water vapor at $\pu{423 K}$. Can I directly measure the energy, contained as heat, within the vapor? All the laws I know depend on knowing the changes that happened that ...
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What does the alcohol functional group (specifically oxygen) have to do that causes an alcohol to have a lower energy content than an alkane? [closed]
My textbook said that the carbon is "partially oxidised" (don't really know what that means) and I just wanted to confirm.
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Prolonging the exothermic reaction between calcium oxide and water
Is it possible to generate 10-minutes of heat using very small amounts of CaO and water? This is an exothermic reaction.
I've done this experiment at home, but it is very short-lived. I'm trying to ...
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Ionisation energy is lower for higher energy shell?
Why does an electron in a higher energy orbital require less energy to remove it? Wouldn't it be harder to remove an electron from a higher energy orbital when compared to a lower energy orbital?
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Atoms in Solar Cells
An electric field in solar cells is created through photons knocking electrons off of atoms. What happens to the positively charged atoms once the electrons have been knocked off? Furthermore, are the ...
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Energy balance for a system [closed]
A hydropower plant uses a river to generate electrical energy. It has a drop of $\pu{107 m}$ and the flow rate of water is $\pu{275 m3 s-1}$. The flow rate of the water is the same in and out of the ...
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polymer/resin/material that melts around 40 C [closed]
Does anybody know of a polymer/resin/material that melts around 40 C and has a high heat of melting, thanks
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Do argon have a high energy? [closed]
Do argon have a large energy density? And what level is it on? Is it weak or have a density like gasoline. How much energy can argon store and what noble gas have the highest energy density?
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Conformational analysis [closed]
In organic chemistry, much emphasis is given to the study of the conformers of alkanes and the broader topic of conformational analysis. Can you elucidate why the spatial arrangements and rotations ...
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