For questions relating to the energy required for or produced by reactions, including questions of endothermicity/exothermicity, bond enthalpy, etc.
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0answers
11 views
Energy change during oxidation of Lithium
I came across this piece of text while reading about the reducing nature of Lithium.
The process of oxidation may be thought to proceed as :
$\ce{M(s)—>M(g)}$ ...
0
votes
0answers
17 views
The energy of ATP phosphate bonds [duplicate]
It is my understanding that there are two principal ways of how energy of bonds can convert into other kinds of energy:
It's released as photons when electrons change their states - and photons can ...
0
votes
0answers
8 views
Titanium Dioxide Self Cleaning Reaction [on hold]
How does Titanium dioxide break down volatile organic compounds and nitrogen oxide? And what is the chemical reaction that occurs?
0
votes
0answers
33 views
hydrogen like atoms spectrum
this question appears in my textbook:
one of the lines in the spectrum of hydrogen-like chlorine ion is
attributed to an electron de-excitation from the 6th energy level to the 2nd
energy level
...
0
votes
1answer
28 views
Shape of the container and the number of possible energy states
A question came up when studying the formula for calculating the total number of possible energy states of a particle within a container.
Why is the number of possible energy states independent of ...
-1
votes
0answers
19 views
Specific heat capacity, internal energy and temperature
When metal and water are exposed to the sun for a certain amount of time , the metal will be burning hot from the sun, but the water will not feel as hot because they have different specific heat ...
1
vote
0answers
52 views
Calculating the number of energy states in a particular momentum direction
Given is a 2D scenario of a particle within a container:
The circumference shows all the possible 2D spatial directions for a given momentum value of the particle. One of those momentum directions is ...
0
votes
0answers
48 views
Observed activation energy of parallel and sequential reactions
I saw this sentence in a test:
Observed activation energy, $E_\mathrm{obs}$, increases with increasing temperature for parallel reactions and decreases with increasing temperature for sequential ...
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votes
2answers
59 views
Carbonyl bond vs alkene bond
Why is that carbonyl bonds are stronger than those of alkenes? It's a basic question but I've never really thought much about it.
I've read several times that carbonyl bonds are shorter and you need ...
0
votes
1answer
40 views
Does the translational part of internal energy mean the kinetic energy of the gas?
Internal energy of an ideal gas consists of energy due to translational, rotational , vibrational etc.
This line from WP says:
In thermodynamics, the internal energy of a system is the energy ...
-1
votes
1answer
16 views
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?
1
vote
1answer
77 views
Why do the 4f and 5d orbitals have similar energies?
I've come to know this phenomena when learning about the exceptions to the aufbau principle. But there is no explanation of why 4f and 5d have similar energies (as I've read in some websites).
0
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0answers
42 views
Planck's Distribution Over a Range of Wavelengths
I am taking PChem this semester and I am stuck on this problem.
Calculate the energy density in the range $\pu{650 nm}$ to $\pu{655 nm}$ inside a cavity at (a) $\pu{25 ^\circ C}$, (b) $\pu{3000 ^\...
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1answer
27 views
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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2answers
93 views
Thermochemistry: What is the difference between the calculation of bond enthalpy and Hess's Law
so I know that hess's law is a indirect way to find the heat of reaction using the known heat of reaction of 2+ thermochemical equation, thus the formula is delta heat of reaction = enthalpy of ...
-1
votes
1answer
318 views
Bond dissociation energy order for C-C,N-N,O-O & F-F single bond
I couldn't understand the trend of bond dissociation energy of various single bonds. Why C-C>N-N>F-F>O-O.
I had mugged up the trend the now, and according to me BDE should continuously increasing ...
0
votes
0answers
54 views
Calculation Radial distribution function using Potential
I am trying to understand an article where it is describing the accuracy of a potential function obtained via a NN (neural network).
To test the ability of the NN potential to describe also ...
-1
votes
1answer
65 views
Thermal Conductivity of Calcium Carbonate?
Is Calcium Carbonate (Group 1 and 2) able to conduct heat more than other carbonate (Transition metal) allowing for them to be decomposed faster. The reason I am asking this question is because my ...
4
votes
2answers
82 views
Tunneling in chemical reactions
We know that quantum tunneling is the reason behind several natural phenomenon like alpha decay and thermonuclear fusion inside the stars. How can it influence chemical reactions by tunnelling a ...
3
votes
2answers
116 views
Does activation energy depend on steric factors?
I thought that activation energy depends on steric factors.
By Arrhenius equation it must depend on steric factors since $A$ depends on steric factors. $$k=A\cdot\mathrm e^{-\frac{E_\mathrm a}{RT}}$$ (...
1
vote
1answer
66 views
How can chemical energy be stored in chemical things like candle wax, gasoline,…? [duplicate]
I have learned about a type of storing energy is chemical energy. But energy isn't sth we can see, can touch. It just simply gives the ability to work. So how can energy be contain in such chemical ...
0
votes
1answer
34 views
How can change in Gibbs free energy ever be positive?
I have a question regarding this formula for Gibbs free energy of a system: $\Delta$G = $\Delta$H - T$\Delta$S.
According to the second law of thermodynamics: T$\Delta$S $\ge$ $\Delta$Q and to my ...
0
votes
2answers
199 views
Could a non-spontaneous reaction occur “on its own”?
Does spontaneity really only apply to the net free energy change of a reaction?
I used to be taught that spontaneous reactions could occur on their own BUT without enzymes or a spark they might take ...
0
votes
1answer
66 views
Quantization and Bohr's model
According to quantization it's said that emitted or absorbed energy is quantized.
Then, when it's said in bohr's model an electron changes its orbit (Let's say it goes to a higher energy shell from $...
0
votes
1answer
96 views
Energy at constant Entropy and Volume
The system of constant entropy and constant volume will attain the equilibrium in a state of minimum energy. Why?
I know that:
$\Delta G= \Delta H-T\Delta S$
And at constant volume and entropy: $\...
1
vote
1answer
57 views
Does the probability function for a molecule to have energy in a certain mode depend on the minimum required quantum energy level of that mode?
I understand that the probability density for a particular velocity v+dv in one dimension for a molecule in a system is:
$$f(v) = \sqrt{\frac{m}{2\pi k_B T}} \cdot e^{\frac{-mv^2}{2k_B T}}$$
I'm ...
0
votes
2answers
111 views
Energy of activation vs Bond energy
In the second chapter, Methane Energy of activation and Transition state in the textbook Organic Chemistry by Morrison and Boyd, Energy of activation is given the following definition:
The minimum ...
3
votes
1answer
522 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 ...
2
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1answer
54 views
Is there any difference between “autoignition temperature” and “ignition temperature”? [closed]
Is there any difference between the "autoignition temperature" and the "ignition temperature" of a substance?
2
votes
1answer
51 views
Reporting reaction energies calculated using electronic energies rather than enthalpies [closed]
I understand that electronic energy includes a combination of
electron-electron repulsion energy,
nuclear-nuclear repulsion energy, and
electron-nuclear attraction energy
at 0 K, and the energies ...
5
votes
1answer
74 views
Dissociation energy of benzene dimer
It is known that the benzene dimer has two stable structures, T-shaped ($\ce{C_{2v}}$) or parallel-displaced ($\ce{C_{2h}}$) structure.
Now the question is: does the dissociation energy ($\ce{D_0}$) $...
1
vote
1answer
98 views
greater bond energy, more stable?
I am very confused about bond energy. In my book, it says "the most stable bond is the bond with the highest bond energy". However, later on it mentions that " A system with low energy is a stable ...
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votes
1answer
67 views
When iodine replaces bromine in 2-bromobutane, does this lead to an overall lower energy level (electrons closer to nucleus) as well?
It seems to me that iodine is a nucleophile that replaces bromine because it has greater attraction to the carbon nucleus due to its electron properties. However, I thought that bonds are formed for ...
1
vote
1answer
40 views
What makes bond break apart from heat? [closed]
What makes bonds break apart from heat?
I am wondering if anyone could explain the reasons why new bonds are formed in the absence of energy. I have found that they form in order to lower the overall ...
1
vote
1answer
250 views
Enthalpy of neutralisation for weak acids and weak bases at standard state
I recently read about why for weak acids and bases the enthalpy of neutralisation is less as compared to the strong ones. This was because the acids and bases being weak, they dissociate incompletely ...
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votes
1answer
48 views
Enthalpy of formaton [closed]
today I was doing a set of HW problems regarding enthalpy and stumble upon one problem that I found confusing.It was the standard enthalpy of formation for CaCO3 is -1207.6 kJ mol when 30.7 g of ...
2
votes
2answers
285 views
Why does a neutral atom of beryllium not have any electrons in a p orbital?
Here's what I understand about quantum number and orbitals, please correct me if anything is wrong:
Electrons enter into these different types of orbitals because they have a higher/lower amount of ...
1
vote
4answers
129 views
How do energy changes in reactions avoid violating the conservation of momentum?
As mentioned in this question, the idea of chemical potential energy explains how the thermal/kinetic energy of particles can change in a reaction; energy is taken in / released by the bonds broken / ...
-1
votes
1answer
66 views
Can oxidation of hydrogen happen in room temperature? [duplicate]
Here is my explanation about the reaction between hydrogen or methane and oxygen.
Hydrogen molecules and oxygen molecules can collide sucessfully and react if they have enough energy. In room ...
1
vote
1answer
53 views
What's the actual or official definition of activation energy? [duplicate]
In some sources I have seen that activation energy is the minimum energy required to cause a reaction. This implies that activation energy doesn't change with temperature (not considering very high ...
0
votes
1answer
71 views
How isotopes atomic mass was defined?
So we say that 1 Amu (u) = 1/12 of the mass of a Carbon 12 atom.
Im not sure about this, but I believe that first we measured the mass of 1 carbon 12 atom (This includes the mass defects that occur ...
2
votes
0answers
41 views
Is it plausible to draw an enthalpy diagram for a nuclear reaction? [closed]
For a project I am required to draw a enthalpy diagram for the conversion of thorium-232 to uranium-233 and I am unsure on how to proceed. I understand a certain amount of energy is lost through beta ...
3
votes
2answers
52 views
Effect of doubling kinetic energy on phase transitions
The kinetic energy of the molecules in a sample of $\ce{H2O}$ in its stable
state at $ \pu{–10 ˚C}$ and $\pu{1 atm}$ is doubled. What are the initial and final phases? [US National Chemistry ...
1
vote
2answers
404 views
Are the breaking of bonds simultaneously endothermic and exothermic? [closed]
I understand that energy is NEEDED to BREAK bonds. But don't chemical bonds already have some form of potential energy in them already? So wouldn't it make sense that even though energy is required to ...
3
votes
1answer
140 views
Am I Using the Correct Number of Significant Figures (Heat Problem)?
The question is:
A patient arrives in the emergency room with a burn caused by steam. Calculate the heat, in kilocalories, that is released when $\pu{18.0 g}$ of steam at $\pu{100 °C}$ hits the ...
1
vote
0answers
60 views
Energy needed for electrolysis of aqueous NaBr [closed]
I'm trying to find the amount of energy it would take to electrolyse sodium bromide to get 1 mole of Br2. I'm not sure how to go about calculating this figure. If anyone could help me out, I'd be very ...
0
votes
2answers
80 views
How can atoms be influenced by light? [closed]
I was watching a SciShow video "Most dangerous Chemicals". It said that a compound called Azidozide azide explodes on being exposed to light. My question is: how does the the atom feel light. Heat can ...
0
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0answers
209 views
Is there a difference between chemical energy and chemical potential energy?
My physics teacher always insisted what was classically called ‘chemical energy’ in lower years, is actually ‘chemical potential energy’ as it has the potential to do work. Is there a difference? Is ...
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votes
1answer
217 views
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 ...
5
votes
1answer
344 views
Is the kinetic energy turning into activation energy when the reaction takes place? [closed]
So I want maybe a simple question that I had on a test today. For a reaction to take place it needs a minimum energy called activation energy. At school I heard that this energy is coming from the ...
