The study of chemical systems using the laws and concepts of physics. This usually requires the techniques of thermodynamics, statistical mechanics and quantum mechanics.

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Calculating the average atomic mass of boron?

Boron has two isotopes with boron-10 and boron-11 having percentage abundance 19.6 % and 80.4%.How do i calculate the average atomic mass? i do know it that average atomic mass is calculated by ...
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2answers
15 views

Reaction involved in Combustion of Nitrocellulose-Nitroglycerine(NCNG) solid propellant?

I'm working on solid propellant based microthrusters and I am using NCNG as the solid propellant. I want to know the reaction taking place and the mass fraction of the products obtained on combustion ...
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143 views

Mistake in Wikipedia article on fugacity?

The Wikipedia Article on Fugacity contains statement The contribution of nonideality to the chemical potential of a real gas is equal to RT ln $\phi$ Here $\phi$ is fugacity coefficient.I think ...
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29 views

Calculating the partition function based on molar heat capacity

Given the molar heat capacity of a partition function as a function of temperature, how would one determine the partition function? Say the molar heat capacity = $\alpha T^2$
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71 views

Proving RTln($a_i$) equal to non PV work done by system,where $a_i$ is activity

We know that chemical potential is defined as ${\mu}_i={\mu}_i^{standard}+RT\ln(a_i)$. Here $a_i$ is the activity of $i^\text{th}$ component of solution. In case of gases instead of $a_i$ it is $f_i$ ...
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21 views

How does the process of protein denaturatation work?

I know it's the proteins that somehow change their properties at some temparature. But what kind of change, in terms of molecule-level structure?
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1answer
27 views

What are the physico-chemical processes at play in ironing of clothes?

The process of ironing of clothes removes (to a large extend) the wrinkles that where introduced in the clothes while drying. Obviously this has to be some physico-chemical process that is ...
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28 views

Activity Coefficients from Electrode Potentials

Lets say we want the activity coefficient of $\ce{Cu^{2+}}$ ions in solution. Would we simply setup one half cell of a $\ce{Cu}$ electrode in a known concentration of $\ce{CuSO4}$ and then connect ...
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2k views

What is the unit of pH?

I'm making some graphs and I have to label the axes. I want to be extra careful and put the units in even though the meaning of $\text{pH}$ is well known. But I have a problem (though a simple one): ...
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28 views

Quotable Literature for the Enthalpy of a Proton

A proton obviously has no electronic energy, no vibrational and no rotational degrees of freedom. Therefore I think it is fair to assume, that $$H(\ce{H+})=\frac32\cdot \mathcal{R}\cdot T$$ holds for ...
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12 views

Eutectic Phase Diagram and Lever Rule

Question: A solution having composition $p$ (left side of graph) is cooled to just above the eutectic temperature (point $s$ is at $ .18 \; x_{Si} $ and the corresponding tie line intersects the ...
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1answer
19 views

how will the pressure of a gas in manometer change if it goes to a place with higher pressure

Imagine a manometer where air pressure is 0.8 atm and the gs pressure is more. We move it to sea level which the air pressure is 1 atm. How the gas pressure changes? (the temperature is constant)
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22 views

What kind of equilibrium constant we use for Gibbs free energy and Van't Hoff equation?

We know that Gibbs free energy is same as negative of 8.314 times temperature in Kelvin times natural logarithm of equilibrium constant, or: Then, we also know Van't Hoff equation, like: (R in ...
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33 views

Calculation of Equilibrium Constant

How do You solve this? $$\ce{2SO2 + O2 -> 2SO3}$$ Starting with $1$ mol of $\ce{SO2}$ and $1$ mol of $\ce{O2}$ in a 1 litre flask, the equilibrium mixture required $0.4$ mol $\ce{MnO4^-}$ in ...
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70 views

What was the misconception about the search of Philosopher's Stone and how does modern chemistry deals with this topic? [closed]

I just read about Alchemy. And it seems to me that many of their principles are closely related to chemistry. So, here is my doubt - Why is not possible to make that alchemist stone called ...
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46 views

What is a simple ratio in which atoms combine?

According to ModernAtomicTheory :- The ratio in which the different atoms combine may be fixed and integral but may not always be simple. The example given is that in sugar molecule the ratio of C ...
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62 views

What is the pKa of the oxonium / hydronium / H3O+ ion?

Although the wikipedia page on Hydronium indicates a pKa of -1.74, I noticed in the discussion of this page that the subject seems debated (cf. http://en.wikipedia.org/wiki/Talk:Hydronium#pKa.3F) ...
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1answer
23 views

How to estimate the dielectric constant of a liquid?

Are there any approximate relationships between the (static) dielectric constant of a liquid and properties of the individual molecules? For example, suppose I know the polarizability and dipole ...
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1answer
24 views

What is the energy change of ethene reacting with hydrogen gas?

$\ce{CH2CH2(g) + H2(g) -> CH3CH3(g)}$ Using this table, source: http://www.kentchemistry.com/images/links/Kinetics/TB08_003.GIF ...
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115 views

Reaction Pathways: What to do when IRC geometries are relaxed (optimized) and the energy changes significantly

The Story: Reaction pathways can be difficult things to deal with using electronic structure methods. Intrinsic reaction coordinates (IRCs) can be determined a number of ways (a discussion of these ...
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58 views

Standard enthalpy of formation (KNO3)

Working on a study guide. I'm a little confused by this question, perhaps my understanding of enthalpy isn't as good as it should be. for the compound $\ce{KNO3}$, which of the following reaction ...
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123 views

Is there an energy cost associated with flipping the spin of an electron?

THE STORY: A common example used to illustrate the limitations of restricted Hartree-Fock (RHF) theory is the H$_2$ dissociation energy ($D_e$) curves. RHF enforces electrons to be paired into spin ...
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51 views

Why isn't ΔG equal to zero for this equilibrium reaction?

In the reaction $\ce{E(g) <=> P(g)}$ at 25°C, equilibrium is reached when the pressure of the product is 0.100 that of the reactant. What is $\Delta G$ in joules? Using $\Delta G = \text{RT} ln ...
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53 views

Hygroscopic behaviour of DMSO - how bad is it?

For a fluid flow experiment I am using DMSO (dimethylsulfoxide), because of its low volatility, reasonably high surface tension, low viscosity and relative safety. In the MSDS of DMSO I find that the ...
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38 views

Is there any way to use syringe pumpe in pumping flow

I want to use syringe pump to pump water at 0.82 ml/min for 30 min ? Is that possible ( I read some paper use that but don't know how ?)
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41 views

What exactly happens to mass during deuterium fusion?

I know that the mass of Helium-4 is slightly less than the mass of 2x Deuterium it may be made of and that it is the reason fusion gives a lot of energy. But where exactly is this missing mass taken ...
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68 views

Do Lithium and Beryllium want to lose electrons to be like Helium?

I can't seem to remember. I know that they all want to fill their valence shells, but, aren't these different?
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3answers
284 views

Boiling point of a liquid increasing with temperature?

In my textbook, a statement is given, as follows: Boiling point of a liquid increases with increase in temperature However, I was wondering, isn't this wrong? The boiling point of a liquid ...
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35 views

Incomplete Combustion products

In class we performed an experiment which I am unable to understand the results for Why does the the amount of soot produced vary? What is the amount of soot produced dependent on? ** Experiment: ...
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1answer
45 views

Testing a sodium aluminate solution

I prepared some sodium aluminate by reacting a strong $NaOH$ solution with aluminium foil and filtering the result. I now have a clear solution and I'm not sure what it is. I stopped adding aluminium ...
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3answers
96 views

Role of heat in combustion

What role does heat play in the combustion process.Specifically, does the amount of heat determine whether complete or incomplete combustion occurs, and is the amount of heat impacted by the amount ...
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1answer
57 views

Most common material in the universe

I was told that 'water' was the most common material in the universe and I disputed that claim. I was met with the argument that hydrogen and oxygen were the most common atoms in the world so water ...
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1answer
30 views

Low-volatile liquids that 'ball-up' on siliconoxide or perfluoroalkanes

This is a very simple and short question. I am looking for liquids that are low/non-volatile at 20$^\circ$C (at least substantially less volatile than water) which have a high contact angle with glass ...
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43 views

What purpose do chain reactions serve?

I just learned what chain reactions are, but I can't seem to wrap my head around them because it seems utterly useless and doesn't accomplish anything. At least that's how I understood it because the ...
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33 views

Conservation of angular momentum in electronic transition

My book says the "angular momentum is always conserved in a transition". But if suppose we have a s electron then it's angular momentum is $\hbar\sqrt{l(l+1)}+\hbar\sqrt{s(s+1)}$ $\implies ...
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1answer
50 views

Why Ionic compounds dissolve into water

First, I would like to say that I understand the basic idea of disassociation and solubility. However, as I study intermolecular forces I feel like this basic Idea is being challenged. My ...
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36 views

Chemistry Elements and Compound [closed]

According to the Bohr theory, what is the significance of full,outer electron orbits of atoms? Which chemical family has this unique property?
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1answer
39 views

Symmetry of an in-phase and an out-of-phase wavefunction “approaching” each other in an MO

Hiho. I have a question concerning this image (Chemistry, Catherine E. Housecroft et al., Pearson Education, 2010). In the text, it states the following: "Each of the new molecular ...
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1answer
366 views

Why electronegativity difference greater than 1.7 are ionic?

I'm learning about how to recognise whether a bond is ionic or covalent bonding. What I have now is a formula: Electronegativity difference = 0 then its nonpolar Electronegativity difference is ...
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47 views

Ground state electron configuration of chromium

What is the ground state electron configuration of chromium? Is it [Ar]4s23d4 or Is it [Ar]4s13d5
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41 views

What are some examples of a clear, liquid, UV photoactive polymer?

Something that is not reactive to lesser wavelengths of light, specifically IR.
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57 views

Is there a way to get hot water without altering plumbing or electrical wiring too much?

Is there a way (other than collecting water and heating it on the stove ) to get hot/warm water from the tap without having to alter existing plumbing or electrical wiring ? EDIT: Perhaps use a ...
2
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1answer
54 views

Why does the equilibrium constant depend on the temperature but not on pressure and concentration?

According to my textbook (and intuitively) certain changes when the aforementioned 3 variables are altered occur in accordance with Le Chatelier's Principle. However, what I don't understand is what ...
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2answers
57 views

Oxyhydrogen applied to a catalytic converter

Recently people have been reporting that if you blow 'HHO' gas (Oxyhydrogen) into a used catalytic converter it gives off excessive heat. Look here for any number of examples. There is a suggestion ...
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1answer
37 views

problem with partial pressures

This is a question I solved in class: At 35 degrees, $\ce{N_2O_4}$ is 15% dissociated in a flask at a pressure of 1.2 atm. Calculate $K_p$ Equation: $$\ce{N_2O_4(g)<=>2NO_2 (g)}$$ ...
3
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2answers
95 views

Equillibrium Constant

I read in my textbook that if we multiply a chemical reaction by some factor(let's say $b$) its new equilibrium constant becomes $K^b$.But I don't understand why this happens.. What is the difference ...
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901 views

Why is the alpha particle called a particle when it is made of four particles?

We know the alpha particle is the nucleus of helium. It contains four subatomic particles - two protons and two neutrons. The protons and neutrons are further made of particles called up and down ...
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25 views

Reaction Rate Limiting Reaction

Why exactly does the slowest reaction limit the instantaneous rate of a reaction even if the faster processes come after? Theoretically, if the products of the slow reaction are required for the fast ...
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2answers
44 views

Specific Case of the Rate law

My textbook says that for a chemical reaction with two reactants, $\ce{A}$ and $\ce{B}$ with equation $\ce{aA + bB -> Products}$, where $a$ and $b$ are coefficients, the general rate law is: ...
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33 views

Deriving the Rate Law

How do you derive the formula for the general rate law? Where does it come from, and why? I know how to use them and get information from them, but not why they are correct. Do they follow from the ...