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

learn more… | top users | synonyms

0
votes
0answers
15 views

combustion energy question [on hold]

When $1~\mathrm{mol}$ of propan-1-ol was burned, the temperature of $6~\mathrm{kg}$ of water increased by $80^{\circ}~\mathrm{C}$. Using this information what is the energy released by the combustion ...
4
votes
1answer
51 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 ...
3
votes
1answer
68 views

How To Get A Double Displacement Reaction Going

So this may be somewhat of a newbie question but here it goes. I was tasked with figuring out how to make some $\ce{NH4ClO4}$(ammonium perchlorate). I found that one way of making it was to react ...
1
vote
1answer
35 views

Comparing adamantane carbon types for accepting OH using MM ForceField

I want to compare two type of carbons accepting OH in adamantane which I've shown below. I know the blue position is preferred. But I wanna prove it with energy optimization and MM Forcefield. I ...
1
vote
1answer
45 views

How to calculate a reaction's DeltaH using a MM forcefield calculator software?

I want to calculate $\Delta H$ for hydrogenation of Benzene and producing Cyclohexane using MM+ Force Field Energy. I am using Hyperchem for energy calculation and optimization. I calculated the ...
1
vote
2answers
51 views

Which formula is correct for calculating the heat of dissolution?

I want to calculate the energy change when a solute is dissolved in water. I know that I can achieve this by using the equation $q=mc \Delta T$. My question is does the mass ($m$) change with the ...
0
votes
1answer
40 views

Why is activation enthalpy found and not just rate of reaction?

What is the benefit of finding activation enthalpy and not rate of reaction?
1
vote
0answers
30 views

First ionization energy of hydrogen molecule

If we have the dissociation's energies of hydrogen molecule $H_{2}$($D_{0}$) and the corresponding molecule ion $H_{2}^{+}$ ($D_{1}$) together with the first energy of ionization of hydrogen atom ...
1
vote
1answer
87 views

How to solve an Arrhenius equation problem?

A widely used rule-of-thumb for the temperature dependence of a reaction rate is that a ten degree rise in the temperature approximately doubles the rate. This is not generally true, especially when a ...
-1
votes
1answer
47 views

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?
2
votes
2answers
92 views

What happens when an explosion can't lead to volume increase of the thermodynamic system?

I have been searching for an answer to the question for a while but was not able to find 1. My question is: What if an explosion is not able to exit the container?-... so lets take a pipe bomb for ...
2
votes
1answer
54 views

Where does the energy of formation of covalent bonds come from?

Consider two $\ce{H}$ atoms. Since the proton in one attracts the electron in another, they attract each other, and form a covalent bond ($\ce{H}-\ce{H}$). Bond forming requires energy (436 kJ/mol for ...
0
votes
0answers
27 views

How is N to C ratio measured in forming austenitic stainless steel?

Nitrogen is the future hope of stainless steel industry; since in the production of austenitic steel it can even completely replace Nickel (which is relatively very expensive) in some cases and for ...
9
votes
1answer
393 views

Why six C atoms are usually seen in cyclic compounds?

When it gets to Carbon-based molecules, one very possible structure when there are more than six C atoms is the hexagon; though not mostly perfect, it emphasizes that six Carbon atoms tend to bond ...
1
vote
1answer
66 views

Is the smallest or largest diameter important for the color of a molecule?

I learned that phenol absorbs longer wavelengths than benzene because the electron cloud is bigger. But what is about Penta-1,2,3,4-tetrien (1) and 2,2,-Dimethylpropane (2)? (1) has the largest ...
0
votes
1answer
37 views

Can we define a new unit instead of specific heat that is constant with temperature rise?

Specific heat plays an important role in calculating energy and thus, heat, enthalpy and etc. But as I sighted the definition for calorie, I was surprised. A calorie is the amount of heat needed ...
1
vote
1answer
24 views

Search materials by HOMO, LUMO and work function

I need to search organic semiconductors for organic photovoltaics (OPV) by their HOMO, LUMO, work function at 300K (as I understand, WF cannot be derived from HOMO and LUMO because semiconductor can ...
2
votes
1answer
27 views

What type of compound/element might be in these glowing tiles

I saw these tiles and these as well while surfing the net, they obiviously glow when their electrons are exited to a higher state and then de-exite over a long period to give off visible light. My ...
2
votes
2answers
24 views

Bond Potential Energy Lowering

"Bonds will form only if the potential energy will be lower when the atoms are bonded than when they are separate." Is this statement true? If so, how do endothermic reactions exist? Can't you add ...
0
votes
1answer
14 views

effect on kinetic energy of a body with change in temperature

Why doesn't the energy of a body doubles when temperature in centigrade is doubled? I know that it doubles in case of kelvin scale
5
votes
1answer
59 views

C-H vs C-C: which is stronger?

I've read that nonpolar bonds are stronger than polar ones. If it is true, why C-H bond entalpy (413) is bigger than C-C (348)? I'm very confused at the moment. Thanks a lot
1
vote
1answer
43 views

What conditions can cause a material to exist as a gas?

So my question is, how can something exist a gas. Is it when the pressure exerted by the gas is greater than the atmospheric pressure, then it is a gas? And also how do manometers work, how can you ...
1
vote
0answers
32 views

How to derive the energy of solvation equation?

The work done as a ion is solvated is given by: $-z^2e^2/8\pi\epsilon r$ but since the top line can be written $Q^2$, for simplicity I will say the equation is $-Q^2/8\pi\epsilon r$. Is this derived ...
1
vote
1answer
65 views

How to calculate the temperature from heat of neutralisation?

The heat of neutralization of $\ce{HCl~ (aq)}$ by $\ce{NaOH}$ is $\mathrm{-55.9~kJ/mol}$ $\ce{H2O}$ produced. If $\mathrm{50~ml}$ of $\mathrm{1.6~M}$ $\ce{NaOH}$ at 25.15 celsius is added to ...
3
votes
1answer
44 views

Transfer of energy

After completing a lab for my chemistry class I am finding it difficult to find the initial temperature of an iron nail after being heated. Procedure of the lab went as follows: heat an iron nail, ...
1
vote
1answer
44 views

“Orthogonality” of chemical elements

Chemical elements are said to be immutable at normal energies, but not at the energies that are orders of magnitude higher. Given that nucleus at normal energies gives us the Periodic Table and at ...
1
vote
2answers
58 views

Electron affinity

Concerning the liberation of energy when an atom that is close to the configuration of a noble gas: Where does the energy dissipated from an atom upon receiving an electron come from?
1
vote
1answer
35 views

Greatest Energy Output Reaction to Atmosphere Air

First of all i'm no chemist, this is not homework and if you need further clarification please ask. I'll be happy to provide! Imagine that you: have 1 kg of any given chemical X A car battery A ...
1
vote
1answer
101 views

Finding Root-Mean-Square of Ne using kinetic energy?

I am not being able to solve the following question: -Find the root-mean-square speed of $\ce{Ne}$ atoms at the temperature at which their kinetic energy is $\mathrm{6.24\ kJ/mol}$. I tried ...
2
votes
2answers
56 views

Energy Calculations using VIt

The answer for Energy in kJ = $2.5 \times 3600 \times 1 = 9000 kJ$ I do not understand what formula they are using... are they using $VIt$, where $V =12$, $t= 12.5 \times 60 \times 60$ seconds and ...
0
votes
1answer
60 views

Explicit differential equation based model of protein folding

I am an applied mathematician interested in the dynamics of potential systems - i.e., systems with multiple unique energy minima. One of the best examples of such systems are protein folding ...
5
votes
3answers
285 views

Is the transformation of pi bonds to sigma bonds always energetically favorable?

Is the move from pi bonds to sigma bonds always favorable? My professor claims so, except in the case of conjugated pi bonds. I can see how pi bonds going to sigma bonds might be favorable; I know ...
1
vote
2answers
101 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 ...
2
votes
0answers
45 views

Delta G values for Pyruvate--> Alanine vs. Oxaloacetate -> Aspartate ->Asparagine

What are the delta G values for the mammalian (human) biosynthesis of alanine from pyruvate, and for the conversion of oxaloacetate to asparagine? (assuming no particular cellular restriction or other ...
1
vote
0answers
55 views

Is S7H4 a chemical?

I want to find a chemical that will react with $\ce{SO2}$ to make water and pure sulfur to battle both greenhouse gasses and drought. I think $\ce{S7H4}$ would do it, but I don't know if it exists. ...
2
votes
0answers
109 views

Activation Energy of a rotting apple [closed]

A slightly bruised apple will rot extensively in about 3.5 days at room temperature (22.0 degrees Celsius). If it is kept in the refrigerator at 0.5 degrees Celsius, the same extent of rotting takes ...
8
votes
3answers
94 views

What really happens atomically in an explosion?

Let's say a room is filled with butane, I then throw a cigarette into the room. What happens to the atoms/molecules of the butane when they are in contact with the heat from the cigarette?
5
votes
2answers
195 views

How can I work out what reaction will happen?

I have recently started learning chemistry, and I've been reading a GCSE (UK high school level) textbook on the stuff :D Much of it has been fairly straightforward, though there has been a ...
2
votes
1answer
110 views

Why is ΔE described as Q-W and Q+W in different contexts?

Depending on the textbooks looked at, the energy change is described as either Q+W or the signage is changed to Q-W. Which is correct? Is it solely context dependent? Could anyone explain the ...
1
vote
2answers
152 views

What is the correct definition of the Gibbs free energy of activation?

Is the following correct? Gibbs free energy of activation is used in energy profiles where the stabilities of the species are expressed as changes in Gibbs energy, while the activation energy Ea ...
0
votes
1answer
163 views

Nitric Oxide Dimerization

This is the molecular orbital diagram for nitric oxide: Now, we know that nitric oxide can dimerize. However, why does nitric oxide dimerize as to form an $\ce{N-N}$ bond? Why not an $\ce{O-O}$ ...
4
votes
2answers
99 views

Nitrogen dioxide dimerization

$\ce{NO}$ can't dimerize and that is explained because the free electron is in an antibonding orbital. The same is true for $\ce{NO2}$, but it can dimerize, how?
0
votes
1answer
27 views

Calorimetry | Heat produced VS Change of enthalpy

There are two questions on the same test paper. Calculate the amount of heat energy, $q$, produced in the reaction Find the change of heat ($-q$). I'm not sure whether or not they mean the same ...
0
votes
3answers
56 views

Why cellphone batteries are still bad?

There are constantly new features in cellphones over the years, but it seems like batteries are not getting any better. Why is that?
5
votes
2answers
155 views

Counting Nodal Planes in cyclopropane

The energy of molecule orbitals increases with more nodal planes. W1 (in the attached picture) has no nodal plane. I'd like to know how to draw the nodal planes in cyclopropane molecule orbitals but ...
0
votes
1answer
68 views

Determining covalent bond strengths without hybridisation

Assuming pure $\ce{2s}$ and $\ce{2p}$ orbitals of carbon are used in forming $\ce{CH4}$ molecule, which of the following statements is false? (single choice question) Three $\ce{C-H}$ bonds ...
2
votes
1answer
119 views

Chemical bonding - lattice energy

Question: Why is ionic lattice energy inversely proportional to the radius of the atom? Most heterogeneous covalent molecules are polar to some extent. The degree of polarity, or the dipole moment, ...
0
votes
1answer
34 views

Is there a possible effect of low frequency mechanical vibration on the stability of organic molecules

Is there a possible theoretical effect of mechanical vibration on the stability of organic molecules. E.g. some medicines degrade if they are not stored in a fridge, is there a theoretical ...
4
votes
3answers
272 views

Is Bond Formation “Strictly” Exothermic?

Is bond formation "strictly" exothermic? The IUPAC definition of exothermic doesn't make any reference to bond formation. However, I have seen the aforementioned statement before - that bond formation ...
2
votes
2answers
134 views

Does any element have nutritional (caloric) value?

Is there any single element (e.g. possibly carbon) that can be eaten, which has nutritional value in that it provides calories? I found on Wikipedia that http://en.wikipedia.org/wiki/Dietary_element ...