Questions relating to heat and its relation to other forms of energy in chemistry.
0
votes
1answer
35 views
How do I know if concentration of Ammonia affected my absorbency measurements?
This is for determination of copper in a penny Lab. After making standard solutions we made a solution with a penny, dissolving it in nitric acid and adding ammonium hydroxide to form a more ...
3
votes
1answer
53 views
Entropy, enthalpy, and reversibility
In my introductory chemistry course, we learned that for reversible processes, entropy is defined as $ΔS = q/T$. However, we did not spend that long on this before moving on to other things like Gibbs ...
0
votes
0answers
22 views
Michaelis Menten Deriviation for 2 Enzyme Substrates
We know that the Michaelis Menten derivation for the following reaction:
$\ce{E + S \rightleftharpoons ES -> E + P}$
Howver, what if the reaction took place in a different scenario whereby:
...
1
vote
1answer
45 views
How hot can Thermal Grease get?
Thermal Grease is used to remove the air gaps between CPU and heatsink. However, computing aside, what would determine the max temp that the grease can handle before it burns or breaks down?
1
vote
1answer
63 views
Thermodynamic Cycle
What is the value for $\Delta_f G^0(\ce{Cl^-}, \ce{aq})$ in this thermodynamic cylce:
Do you agree it should be (with the formation free energy of $\ce{H^+} = 0$)
$$-\Delta_f G^0(\ce{Cl^-}, ...
3
votes
1answer
71 views
How is hydration free energy of a solute measured experimentally?
I am reading a paper (Shirts, M. R.; and Pitera, J. W. and Swope, W. C. and Pande, V. S. J. Chem. Phys. 2003, 119, 5740-5761). Near the beginning of the paper (page 5745), the authors state:
...
0
votes
2answers
244 views
When is it okay to use $Q=mc\Delta T$, is this equation only for calorimetry questions?
When is it okay to use $Q=mc\Delta T$, is the equation only for calorimetry questions? When a question talks about heat how do I know if i'm measuring $\Delta H$ or Q?
2
votes
0answers
39 views
Question Regarding the Chlorine Dioxide-Iodine-Malonic Acid Reaction
After reading a section on this particular oscillatory reaction, something started bugging me about it.
However, let me lay out the basis of my question. From what I've researched, Lengyel and ...
0
votes
1answer
73 views
Spontaneous inequilibrium in a gas in an isolated system?
Can an isolated system(of several phases) in equilibrium by itself move out of equilibrium?
if a system contains for example an inflammable gas dispersed with another combustible gas such that the ...
5
votes
2answers
96 views
Measuring Thermodynamic Stability
We can predict whether a reaction can occur spontaneously by calculating the change in Gibbs' free energy.
I was just wondering whether there is any general measure of the thermodynamic stability of ...
1
vote
1answer
43 views
Hot and cold air interaction in a sealed environment
What would happen if air heated to 1200 degree's Fahrenheit in a sealed environment was injected with colder air?
No specific pressure defined yet just a general idea of potential interaction between ...
0
votes
1answer
68 views
Thermodynamic Laws: Is there some kind of pun in this picture? [closed]
I just encountered this picture on the web. I didn't understand its intent.
3
votes
1answer
68 views
Influence of solubility at different pHs on the complexation constants
Given some small chemical compounds whose solubility varies with pH, and in the case of compounds that can form complexes, I have seen that the complexation constant varies with pH. I think there ...
3
votes
1answer
34 views
Nitrogen triodide energetics
Ammonia has a heat of formation of $-46 \:\mathrm{kJ/mol}$ (which means that it's formation from the elements releases heat). When mixed with iodine at room temperature, it makes nitrogen triodide ...
1
vote
1answer
23 views
Is it possible to form bubbles of ionized hydrogen and ionized oxygen under the right pressure/temperature conditions during electrolysis of water?
When we run a current through water (pure or not), $\ce{O_2}$ forms at the anode while $\ce{H_2}$ forms at the cathode. If I understand correctly, as water is already slightly ionized, $\ce{H}$'s snap ...
1
vote
1answer
53 views
Software for chemical reaction simulation in ICE
I want to study what happens in a internal combustion engine in which fossil fuels are mixed along with other chemical additives.
Example:
Acetone drastically reduces surface tension.
Most fuel ...
2
votes
2answers
88 views
Calculating heat capacity of a calorimeter
I am struggling on this question :
The heat of neutralization of $\ce{NaOH}$ and $\ce{HCl}$ is $-57.1\:\mathrm{kJ}$, calculate the numbers of moles of $\ce{HCl}$ and if $x$ moles of $\ce{HCl}$ were ...
4
votes
2answers
1k views
Difference between thermodynamic and kinetic stability
What is the difference between thermodynamic and kinetic stability? I'd like a basic explanation, but not too simple. For example, methane does not burn until lit -- why?
6
votes
6answers
831 views
What is a pure substance?
I found as I was preparing to teach "Introduction to thermodynamics" that there are varying definitions or examples of pure substances. For instance the text book I have to use "Thermodynamics an ...
5
votes
1answer
70 views
What defines matter's phase at room temperature?
So, a simple question: what makes neon a gas; what makes water liquid; what makes plutonium-238 a solid at room temperature? Of course, the phase is determined by the excitation of the molecules, but ...
5
votes
1answer
53 views
Lennard Jones liquid vapor phase transition
I am trying to generate a phase diagram of pressure versus temperature in a NPT ensemble using molecular dynamics method. I am using the Lennard Jones potential with 108 particles and Berendsen ...
1
vote
1answer
48 views
Heat required to melt Benzene
How much heat is required to melt 75 grams of Benzene at 278.6 Kelvin? I don't understand can someone help me?
3
votes
1answer
82 views
Source for thermodynamic and/or transport properties
I'm working on some combustion problems using Cantera and I can't find references for the thermodynamic or transport properties for many of my chemical species. I'm looking for NASA-7 or NASA-9 ...
3
votes
2answers
233 views
Non-Commercial Thermal Insulation
I am trying to create a small 10 to 20cm cube that can conserve the heat in 100 to 200ml of 60-90c water in a small Pyrex glass for about an hour. The problem is that I can not use commercial ...
2
votes
1answer
180 views
Why can dissolution reactions (e.g. dissolution of calcium chloride) be exothermic?
Dissolution reactions are normally endothermic, and crystallization reactions are normally exothermic, but there are some exceptions -- such as the dissolution of calcium chloride. Why is this so?
0
votes
0answers
64 views
Chemical potential intuitively [closed]
Can you please give me an intuitive explaination of the Gibbs free energy or the chemical potential, and also the difference between them and the enthalpy?
2
votes
1answer
100 views
Is an explosion merely an exothermic reaction?
An exothermic reaction is apparently one that releases energy to it's environment. According to Wikipedia, an explosion is a rapid increase in volume & energy.
Does this mean that an explosion is ...
0
votes
1answer
49 views
Problem with a calorimeter (theoretical)
Given $2.14g$ of $K_{(s)}$, determine $\Delta Hº_{f,m}$ and $\Delta Uº_{f,m}$ for $K_2O$.
We know:
The calorimeter's constant: $1849J•K^{-1}$
The mass of water inside it: $1450g$
The change in ...
3
votes
1answer
40 views
Question about fire and colors
Most solids objects turn black after they are burnt.
But some turn white.
Why is that ?
4
votes
1answer
69 views
Find mass of CO₂ and heat released per minute in a combustion reaction
I am not sure where to start with this problem. I know that $\small q = mc(T_f-T_i)$, but that seems like it would not help here. I think I need to balance the equation, but I am not sure how the rate ...
6
votes
1answer
202 views
Calculating entropy: why consider a reversible path?
I am reading up on entropy in a textbook and I got confused by this:
It says that to calculate the entropy for an irreversible process using heat flow, one must imagine the reversible process in ...
2
votes
1answer
87 views
Are there any nonflammable thermal insulators which can be made at home?
I am trying to build a homemade thermos. It needs to be able to conserve the heat in 125ml of water for 15 minutes.
However, unlike a normal thermos, it also needs to be able to be heated. What ...
3
votes
2answers
232 views
What are the chemical reactions behind fire?
I've always wondered what the chemistry behind fire is. What are the basic chemical reactions behind a simple wood fire, and how do they manifest into this phenomenon?
3
votes
1answer
100 views
Is there a way to calculate how fast water will cool?
Is there a way to calculate how fast water will cool if you know the water's starting temperature and temperature of the environment that you put it in, such as a freezer?
1
vote
0answers
18 views
Find flow rate of the aqueous current needed to process benzene-hydrochloric acid solution
I am trying to understand if my reasoning is right, as my exam is getting closer and I would really appreciate any feedback, I'd be very pleased to know if I have made any mistakes in solving this ...
1
vote
1answer
123 views
Is “ice point” the same as “freezing point”?
I am using an old book and they almost use both terms interchangeably sometimes. Do they mean the same thing? Similiarly for "steam point" and "boiling point"
4
votes
3answers
356 views
Methane seems to dissolve more readily in cold water. Why?
http://www.watertechonline.com/drinking-water/article/the-fine-points-of-methane-removal
When you are diluting air in the system and/or properly evacuating it, you must consider water temperature. ...
4
votes
1answer
134 views
What is known about the phase of matter at very high temperature and enough pressure?
Are there theoretical reasons for or against the existence of materials that will not become solid at some fixed, sufficiently large temperature when enough pressure is applied? Or is this even the ...
8
votes
4answers
117 views
standard reference for thermodynamic properties?
I'm a non-chemist attempting to put together a chemistry paper. Up to now I've got my thermodynamic data from various random pdf files found on the web, together with Wikipedia. Now that the paper is ...
1
vote
1answer
517 views
How to calculate entropy change for a gas reaction using $S^\circ$?
I'm calculating molar changes in thermodynamic properties due to reactions between gasses (assumed to be ideal gases). I can calculate $\Delta H$ easily enough, because it's just $\sum_i ...
2
votes
0answers
43 views
How can I compute the temperature change from the de-excitation of excited particle species?
The motivation for the question in the title is that I have some formula given,
$$\Delta T=\frac{3410\ \gamma_{O_2}}{2.5+\gamma_{O_2}},$$
where $\gamma_{O_2}$ is the molar fraction of oxygen in a ...
2
votes
2answers
595 views
What is the difference between temperature and thermodynamic temperature?
My course book says that kelvin is the unit of thermodynamic temperature, then what is the difference between temperature and thermodynamic temperature.
2
votes
0answers
194 views
Deliquescence/efflorescence: How can I convert between salt concentration and RH?
I am looking at two phase diagrams, one has axes of $T$ and $\%\ce{MgClO4}$ in a $\ce{H2O-MgClO4}$ mix, and the other has axes of $T$ and relative humidity. The authors of the second phase diagram say ...
5
votes
1answer
98 views
Where can I obtain tables of P-V-T/compression factor data?
Some recent research I'm dealing with has required me to look for tables of experimental pressure/volume/temperature values (equivalently, a table of compressibility/compression factors in terms of ...
3
votes
0answers
61 views
Difference between non-thermal and thermal ionized gases
Why or when does non-thermal plasma become thermal? How do we know before hand if the ion temperature will differ from the electron temperature, on what parameters does it depend - where is the ...
4
votes
2answers
298 views
Temperature dependence in absorption spectroscopy
What are some qualitative guidelines one should know regarding the temperature dependencies (of the gas and maybe the radiation, if that makes sense) for an absorption spectroscopy measurement?
How ...
3
votes
1answer
74 views
What is the difference between an ionic and molecular activity model? (Example: Diopside-Hedenbergite)
Original question:
When looking at a Diopside-Hedenbergite solid solution, what is the difference between an ionic and molecular activity model? Why does the moleclar model yield higher values?
...
6
votes
2answers
238 views
What is a rigorous definition of gas volume, and how is the Van der Waals equation derived?
I am confused about the justification for the corrections to the ideal gas law in the Van der Waals equation: $$p=\frac{nRT}{V-nb}-a(\frac{n}{V})^2$$
I understand that the equation attempts to ...
5
votes
2answers
610 views
Is the specific heat of liquid iron constant?
Does liquid iron have a constant specific heat capacity? Everywhere I've looked (save one sourceless online reference to $C_p$ = 611 J.kg–1.K–1 here), I find no value listed for liquid iron. Is this ...
8
votes
3answers
301 views
Is enthalpy additive in mixing?
When mixing two fluids of different composition at constant pressure when no heat can escape, is the enthalpy additive?
If not, how to compute the enthalpy of the mixture resulting from mixing two ...
