Questions tagged [energy]

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

Filter by
Sorted by
Tagged with
-1
votes
1answer
21 views

Comparison of energy release from different types of fuels

I've recently been reading about the different amount of energy release for different types of fuels/hydrocarbons. Anyways, I was wondering why butanol would release more energy (kj/mol) than methanol?...
-2
votes
0answers
71 views

Delocalisation in Anti-Aromatic compounds

Recently, while solving questions on aromaticity, I came across a fact (as mentioned in the solution key of the question set) that there is NO DETECTABLE delocalisation in Anti-Aromatic compounds. ...
0
votes
0answers
29 views

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 ...
-2
votes
2answers
70 views

How do you know what elements will bond in a reaction? [closed]

I know all about the types of reactions, synthesis, decomp. etc., but when a bond is broken, how do you know that the free element will bond to another molecule? Is it because that element has a ...
2
votes
1answer
187 views

How to figure out the most stable conformation of the diastereomer?

I guess my main question is looking only at the newman projection how does one determine the stereochemistry? In the molecule to the right, I get for the first carbon, (et, H, Me,) R ( I flipped it ...
5
votes
0answers
61 views

Solving the Schrödinger equation for a rotating triatomic linear molecule

This source is showing that solving the Schrödinger equation for a triatmoic linear molecule yields the same formula for the rotationaI quantum states $BJ(J+1)$ as for dipoles. For dipoles, the total ...
5
votes
1answer
3k views

Difference between dissociation energy and dissociation temperature for water?

I was trying to find the temperature at which water dissociates into hydrogen and oxygen, and so I came across this Wikipedia page. It states that it takes $\pu{493.4 kJ/mol} + \pu{424.4 kJ/mol}$ to ...
-2
votes
2answers
52 views

The relation between q and T when the volume is constant [closed]

$$ \begin{align} q_V &= ΔU \tag{1}\\ q_p &= ΔH \tag{2}\\ C_V &= \frac{\mathrm dq_V}{\mathrm dT} = \left(\frac{\partial U}{\partial T}\right)_V \tag{3}\\ C_p &= \frac{\mathrm dq_p}{\...
-2
votes
2answers
52 views

What does it mean for chemical reactions to release energy?

My Physics textbook gives the following definition of energy : The capacity of a body to do work is defined as the energy possessed by it This was the definition that was used to derive $U_G = mgh$ ...
2
votes
1answer
69 views

Calculation of free energy from potential and kinetic energy

I am having trouble understanding how (and even whether it's possible) to get free energy from kinetic and potential energy. I have run molecular dynamics simulations (NPT ensemble, CP2K software), ...
5
votes
1answer
2k views

Why the energies of orbitals in the same subshell decrease with increase of atomic number?

Why the energies of orbitals in the same subshell decrease with increase of atomic number? For eg., energy of 2s orbital of hydrogen atom is greater than energy of 2s orbital of lithium atom. What is ...
3
votes
1answer
374 views

Uses of ruthenium-106?

I read a news article recently about a cloud of ruthenium-106 being released over Europe. The article mentioned one of the uses for this specific isotope is in fuel cells for satellites. I tried to do ...
5
votes
2answers
380 views

Pressure exerted by a particle of ideal gas

There is a step I fail to grasp in the proof that for a monatomic ideal gas, $U=\frac{3}{2}PV$, where $U$ denotes the internal energy of the gas. The proof involves considering a particle with mass $m$...
2
votes
1answer
2k views

Finding root-mean-square speed of neon using kinetic energy

Find the root-mean-square speed of $\ce{Ne}$ atoms at the temperature at which their kinetic energy is $\pu{6.24 kJ mol-1}.$ I tried using the kinetic energy formula $$\mathrm{KE} = \frac{mv^2}{2},$$ ...
0
votes
0answers
9 views

Measurement of Energy Density

I'd like to ask how researchers measure/calculate the energy density for chemical fuels? Do they just measure the enthalpy change of combustion (△H combustion) in a calorimeter and then divide it by ...
9
votes
3answers
38k views

ATP break down and energy release?

I have a very basic question. Energy is absorbed to break bonds. Bond-breaking is an endothermic process. Energy is released when new bonds form. Bond-making is an exothermic process. But ATP breaks ...
-1
votes
1answer
35 views

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.
0
votes
2answers
318 views

What is the first ionization energy of the hydride ion?

What is the first ionization energy for hydride? Since there are two electrons in the s orbital, I suppose it should be more stable than hydrogen, despite the extra electric charge, so the ionization ...
-4
votes
1answer
52 views

how to calculate the dihedral angle [closed]

I need to calculate the dihedral angle between C20 and C19, as well as between C19-C18. Can someone help me choosing the right combination? I have used the following one: C18C19C20C23 for the first ...
0
votes
1answer
31 views

Why are bonded ions more stable than separate ions? [closed]

I was reading on the Born-Haber cycle when I encountered a problem. The textbook seemed to suggest that since energy must be supplied to separate an ionic compound into it's composite ions, then the ...
0
votes
0answers
23 views

What is the link between the classical and quantum definition of the symmetry number?

From what I understand, the symmetry number for a molecule can be defined in 2 ways: 1. The quantum mechanical symmetry number corrects for overcounting the number of possible rotational states of a ...
2
votes
1answer
64 views

How do we figure out whether reactions are endothermic or exothermic? [closed]

Are the following reactions exothermic or endothermic: $$\ce{H2 + I2 -> 2HI}$$ $$\ce{N2 + O2 -> 2NO}$$ So I know the second reaction is endothermic as we need to break triple bonds between ...
2
votes
1answer
67 views

What's the minimum amount of energy needed to remove CO2 from the atmosphere?

I've been learning about CDR (Carbon Dioxide Removal) techniques to combat climate change. These all seem to involve extracting $\ce{CO2}$ from the atmosphere and converting to a mineral, which is ...
3
votes
2answers
3k views

Formulas for the number of spectral lines

While reading through Narendra Avasthi's Problems in Physical Chemistry, I came across two formulas on p. 64 (Scanned page): When electrons de-excite from higher energy level ($n_2$) to lower ...
-2
votes
2answers
29 views

What is the difference between enthalpy change and energy change? [closed]

This question seems really dumb but I rather be safe than sorry. I read about enthalpy change in my chemistry textbook which defines enthalpy change as the energy exchange between a chemical reaction ...
2
votes
0answers
116 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 ...
2
votes
1answer
315 views

Why does aluminum chloride have a higher lattice energy than aluminum fluoride?

From the table below (source: McMurry's Chemistry [1, p. 212]), it is evident that $\ce{AlCl_3}$ has a higher lattice energy than $\ce{AlF3},$ even though $\ce{F}$ is smaller than $\ce{Cl}$. Why is ...
10
votes
1answer
347 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 ...
0
votes
0answers
13 views

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 /...
0
votes
1answer
56 views

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 ...
1
vote
1answer
36 views

Is enthalpy affected by isotopes?

Enthalpy is a sum of $U$ and $PV$, and I thought that for different isotopes, internal energy values may differ. Is it true? There are three stable isotopes of $\textrm{Mg}$, mass number 24, 25, and ...
0
votes
0answers
49 views

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}...
4
votes
0answers
24 views

Covering conformers in a molecular modelling; consider them as a static entity or work with modelling shifts as well?

I am currently working with a molecular docking project, examining potential affinities of a solvent on a protein in an assay to evaluate potential error margin. The solvent is cyclohexanol (referred ...
-2
votes
1answer
3k views

Why is pi bond in N=N stronger than sigma bond? [closed]

Bond energy for N-N is 163Kj/mol whereas bond energy for N=N is 418kj/mol even though it should be lesser than twice bond energy for N-N. Why is that? For carbon it is: Bond energy for C-C ...
-2
votes
1answer
24 views

How value of energy of elecron becomes more negative and radius of orbit decreases with increase in the value of atomic number? [closed]

I know how energy of elecron and radius of orbit depends upon principal quantum number......But how it depends upon atomic number?
2
votes
1answer
50 views

Does the absolute value of enthalpy have any physical significance?

I know it is pretty hard to measure the change in volume in open systems. Accordingly, calculating the change in internal energy using the first law of thermodynamics is pretty hard also. Is this the ...
3
votes
3answers
4k views

In nuclear chemistry, how does a neutron split to form a proton and an electron?

I'm studying radioisotopes at the moment and balancing nuclear reactions isn't making sense in that more matter is coming out of the equation in negative β⁻ decay equations: $$\ce{_6^{14}C -> _7^{...
-2
votes
1answer
65 views

Why do stable compounds have a lower heat of combustion?

My brain somehow doesn't accept that more stable compounds require have less enthalpy. Isn't it like, if a compound is stable, it requires more energy to break the bonds because the compound doesn't ...
1
vote
1answer
6k views

Energy Diagram for Propane

I've been unable to find an energy diagram for propane either in my book or online via Google. So I resorted to making my own. I suspect that propane isn't covered because it's essentially the same ...
0
votes
0answers
20 views

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-...
1
vote
0answers
22 views

Why is average bond enthalpy measured by homolytic fission?

Average bond enthalpy: the energy required for 1 mole of a specific gaseous bonds to undergo homolytic fission Why specifically homolytic fission? Is it to allow comparison, but if that were the case,...
0
votes
1answer
73 views

Difference between chemical energy and potential energy

I know that chemical energy is the potential energy stored in the arrangement of atoms within molecules. Forming new chemical bonds releases energy. what does potential energy mean? Is it the energy ...
0
votes
0answers
22 views

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....
0
votes
0answers
31 views

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 ...
3
votes
3answers
422 views

Which substances have the highest/lowest enthalpy of formation per gram?

Which substances have the most extreme enthalpies of formation per gram at standard temperature and pressure?
7
votes
1answer
14k views

How do I distinguish between internal energy and enthalpy?

I am finding it hard to distinguish between the two. Can someone explain the two terms and the difference between them? I tried learning from Wikipedia, but it said for both the above terms that it ...
3
votes
4answers
2k views

Does any element have nutritional (caloric) value?

Is there any single element (e.g. possibly carbon) that can be eaten, which has a nutritional value such that it provides calories? I found on Wikipedia (dietary element) that there are certain ...
1
vote
1answer
124 views

Values for heat of reaction example

I am currently studying the textbook Mass Spectrometry, third edition, by Jürgen H. Gross. Chapter 2.4.3 Bond Dissociation Energies and Heats of Formation says the following: Energetics of $\ce{H}^\...
3
votes
1answer
8k views

How hot is elephant toothpaste?

So, I remember in high school chemistry when my teacher combined hydrogen peroxide with potassium iodide and it exploded into a yellowish foam. He said it was an exothermic reaction so it's really hot....
1
vote
1answer
61 views

Endothermic or Exothermic [closed]

Is an endothermic reaction always endothermic at all conditions of pressure, temperature etc.? Similarly for exothermic... I mean is sign of ∆H always the same as sign of ∆H°? This might seem to be a ...

1
2 3 4 5
11