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

learn more… | top users | synonyms

1
vote
0answers
14 views

Ionisation Energy (removal of electron) [on hold]

My question is: Relate the ease of removal of an electron to the charge on the most stable ion formed by the element?
4
votes
1answer
33 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 ...
-2
votes
1answer
32 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 ...
1
vote
1answer
84 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 ...
2
votes
2answers
49 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 ...
4
votes
1answer
34 views

Why is 2-methylpropene less in energy than its alkene counterparts?

Other isomers include 1-butene, cis 2-butene, and trans 2-butene. Why would 2-methylpropene be less in energy if there is more steric hindrance?
0
votes
1answer
54 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 ...
1
vote
0answers
22 views

Why does the electron affinity increase in the 15th group

Why does the electron affinity increase by going down through the 15th group?
6
votes
2answers
121 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 ...
0
votes
0answers
6 views

What is the heat of dissolution of sodium acetate trihydate?

Is the reaction endothermic since its crystallization is exothermic?
1
vote
1answer
18 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 ...
4
votes
1answer
59 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 ...
2
votes
0answers
30 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 ...
2
votes
1answer
35 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 ...
1
vote
1answer
32 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 ...
1
vote
0answers
47 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 ...
1
vote
2answers
31 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?
1
vote
2answers
55 views

Gibbs free energy or reaction enthalphy

If I conduct a reaction say, $$\ce{CaO(s) + H2O(l) \rightarrow Ca(OH)2 (aq)}$$ let us say , I want to measure the energy generated from the reaction.Will this energy I calculate equal the change in ...
6
votes
1answer
254 views

Does the “Bat Gen” claim to produce more energy that it uses?

These links claim that inventor Arturo Solis Herrera has created an "everlasting battery". http://www.mexiconewsnetwork.com/news/bat-gen/ http://www.faqs.org/patents/app/20090134007#ixzz10Sh9iLQM ...
2
votes
1answer
91 views

What tools can be used to estimate binding energies?

I want to estimate the binding energies of various molecules. What are the analytical and numerical tools I can use for this purpose? In particular I'm interested in bonding energies of dyes to ...
4
votes
1answer
94 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
109 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
46 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
56 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 ...
2
votes
2answers
101 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
42 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
38 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
276 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
60 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
97 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
79 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
30 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 ...
10
votes
1answer
439 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
97 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
38 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
40 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
32 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
32 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
98 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
48 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
37 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
100 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
54 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
46 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
59 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
37 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
139 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
66 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
65 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 ...