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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Why is the enthalpy of vaporization greater than the enthalpy of fusion?

Why us the molar enthalpy of vaporization of a substance is larger than its molar enthalpy of fusion (at constant pressure); for example, in the case of ice and water.
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43 views

Intermolecular Hydrogen Bonding

I learnt about intermolecular hydrogen bonding today, which occurs between molecules such as ortho-nitro-phenol. What I was told is that in case of intermolecular bonding, the molecules separate from ...
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35 views

What is the mass of 1 Liter of ethylene at 2000 bar pressure?

I was wondering the weight of 1 liter of ethylene at 2000 bar and 310 Kelvin? I have tried to just multiply the weight at 1 bar with 2000 but I don't think i got the correct answer because the answer ...
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227 views

What is Sodium Chloride like in gas state?

Since sodium chloride is sodium and chlorine atoms bonded as a lattice and there are no discrete molecules, doesn't that mean in gas state, sodium chloride is simply sodium and chlorine atoms separate ...
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40 views

What is the simplest structural unit of an element or compound?

From "Smarter than a 5th Grader": What is the simplest structural unit of an element or compound? molecule, atom, neutron, proton For covalent compounds, the answer would ...
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3answers
55 views

What is reactivity really, and can it be quantified?

I understand the concept of a reactive species on a sort of vague and intuitive level: a reactive species is one that has lots of reactions that it can participate in. These tend to have large kinetic ...
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27 views

How can we say that one mole of a substance contains avogadro number of particles?

I just want to know, what was the procedure through which the value of one mole of a substance was considered as a an aggregate of $6.023\cdot10^{23}$ particles. Secondly, how do we calculate the ...
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2answers
14 views

Chemical reactions in SFE?

What are the chemical reactions and/or chemical processes that take place during SFE(supercritical fluid extraction)? Namely supercritical $\ce{CO2}$.
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37 views

Reconciling the units of pH calculation

As part of a simulation I am developing I have an acid in aqueous solution represented as a concentration field of mass density (units g/L) at various points in ...
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34 views

Solar still and how it works

I use a solar still that holds 182 cubic feet of water. Here is how it works: There is an insulator on both sides of the metal bowl. On the outside it covers the whole thing. on the inside it covers ...
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37 views

Units for dissociation constant and relationship to Gibbs Free Energy

How does one "convert" between an equilibrium constant calculated from the Gibbs free energy for a dissociation reaction and experimentally determined dissociation constants? $$ \Delta ...
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44 views

Why does the lone pair of phosphine not contribute to its dipole moment?

Unlike ammonia,the lone pair of phosphorous does not add to the dipole moment of phosphine. My textbook says this is due to the presence of lone pair of phosphorous in $PH_3$ in $s$ orbital. I ...
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78 views

How does lone pair of a central atom affect the dipole moment?

Dipole moment is the degree of polarity ie. seperation of positive and negative charges. But I am not getting the intuition why and how lone pair affects the polarity and dipole moment.I cannot ...
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16 views

How can we calculate enthalpy change in a closed tank containing methanol adsorbed by activated carbon?

Here's the problem in the simplest way: I have a closed box containing methanol adsorbed by activated carbon. The box is made from copper. A pipe is connected to that box, which has condenser on the ...
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11 views

Simulating enzymatic change rates of Carbonic anhydrase

I'm trying to simulate effects of carbonic anhydrase on cellular pH as caused by changes in bicarbonate. I assume a bicarbonate homeostatic mechanisms which replenishes intracellular conenctrations ...
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28 views

Can a clay brick waste in a soil be a source of minerals for plants?

Clay brick is made by heating them so their clay structure changes. What i understand is ultimately all materials have one or another base minerals in it particularly here this brick still it remains ...
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52 views

Does the distance increase as the polarity increases?

According to the dipole moment's definition, as polarity increases the distance between the centres of positive charge & negative charge increases.In the ionic bond ,as the polarity is maximum, ...
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25 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 ...
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38 views

Finding the initial concentration

The solubility product of $\ce{AgBr}$ is $7.7 \cdot 10^{-13}\:\mathrm{mol^2/L^2}$. What was the initial concentration of $\ce{AgNO3}$ solution, if the precipitation of $\ce{AgBr}$ appears after the ...
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37 views

production rate from chemical reaction [closed]

I have the following reactions (1)$\ce{NaOH+CO2+M=NaHCO3+M}$, K1 (2)$\ce{NaHCO3+H=Na+H2CO3}$, K2 (3)$\ce{2NaHCO3+M=(NaHCO3)2+M}$, K3 ki's are the rate constants. Suppose $\ce{NaHCO3}$ is a ...
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41 views

Calculate the molality and molarity of this simple solution

Concentrated hydrochloric acid contains 37% (by mass) $\ce{HCl}$. The density of its solution is $\mathrm{1.18 g/ml}$. Calculate the molarity and molality of the solution.
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17 views

What is relationship between molecular weight distribution of PE and its strength?

I'm trying to figure out the relationship between the molecular weight distribution of a polyethylene plastic and its strength and heat sealability. (The molecular weight distribution is described ...
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1answer
27 views

What is defined by part by weight in the definition of equivalent weight?

Acc. to my book,equivalent weight is defined as the 'number of parts by weight' of an element that interacts with $1.008$ parts by weight of hydrogen.It is dimensionless while gram equivalent weight ...
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50 views

Finding overall order of reaction

Recently I've been going through an exercise of Chemical Kinetics and Nuclear Chemistry and right now I am stuck to one. Question was previously asked in JEE(Advanced)-2013. The question says, In ...
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42 views

Why solubility of Group II hydroxides increase down the group and sulphates decrease down the group?

I know that, solubility of alkaline earth metal hydroxides increases down the group and solubility of alkaline earth metal sulfates decreases down the group. Would you please explain me the reason ...
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56 views

Explanation for the reactions in a saltwater battery with zinc and copper electrodes

I am a physicist, not a chemist. I'm trying to get a basic understanding of the reactions taking place in a battery using a saltwater electrolyte with copper and zinc terminals. I'm writing a general ...
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Atmospheric Humidity Effects on Non-water Evaporation

Does evaporation of non-water liquids into the atmosphere vary with atmospheric humidity?
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18 views

Empirical and Molecular Formulae

I'm not a chemist, and nor do I study chemistry so please try to be gentle. Glucose has the molecular formula $\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$ and the empirical formula ...
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44 views

Reduce sizing of molecule - Oxygen

Can the size of molecule oxygen reduce smaller? If yes, how is that possible? Is it related to proton and electron surrounding the nucleus?
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34 views

Specific Heat of Water Solution

If we add an ionic solute to water, will the specific heat of the water be increased or decreased? I understand that the specific heat is a measure of how much energy we must add to water for the ...
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3answers
19 views

Hess Cycle, determining enthalpy change of formation

I am asked to find the enthalpy change of formation of the following: $$\ce{N2 + 1/2O2 -> N2O}$$ I am given the following enthalpies of reaction: $$1:\:\ce{C + N2O -> CO + N2} \:\:\:\Delta H_f ...
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31 views

Finding out the number of atoms in the sun.

This is the question from the text book: This is what I did, since it worked with all the previous questions (similar to this). $$ \frac{\frac{4}{3}\pi(7*10^8)^3*1.4}{1.008} * 6.022*10^{23} $$ ...
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26 views

Number of collisions of particles in a box (or a sphere)

Imagine you randomly spread in a cubic space of volume $m^3$ (or in a sphere of volume $V_s$, as you prefer), $n_A$ particles $A$ and $n_B$ particles $B$. Particles $A$ are spheres of volume $V_A$ and ...
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Graph theory, isomer enumeration and chemical graph theory

Where could we find a good description of graph theory applied to the general problem of isomer enumeration and chemical graph theory?
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Making a reasonable slab of alpha quartz

I want to perform a molecular dynamics simulation with alpha-quartz as my mineral surface. I want to study adsorption of water on alpha-quartz. The most dominant error that I came up with is the ...
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Why doesn't a table sublimate, while ice does?

A table does not sublimate, and nor does a spoon. Ice does, however. What is the fundamental difference?
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57 views

How to calculate the number of moles present in a litre of saturated solution?

The solubility product of a salt having same molecular formula as $\ce{Ca_3(PO_4)_2}$ is $1.08\cdot10^{-28}$. Then find the number of moles of ions present in the saturated solution. My approach: I ...
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117 views

Relationship between magnitudes of forward and reverse kinetic rate constants

Consider the reversible unimolecular reaction: $A \overset{k_{1}}{\underset{k_{2}}{\rightleftharpoons}} B$ We know that the forward reaction is often considerably more thermodynamically favourable ...
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39 views

What attributes cause a substance to be nonconductive or conductive

I understand what causes elements to be conductive or nonconductive. But what causes a substance say rubber to be nonconductive at a molecular level?
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59 views

Semi-Infinite Potential Square Well: Negative Potential

I am having trouble with a problem involving a Semi-infinite potential square well: I have written down some notes that I added to the post. I have problems understanding the physical situation. See ...
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1answer
37 views

pH of a solution of acetic acid and ammonium acetate

After studying ionic equilibrium, I was just making some wild questions and I was unable to calculate the $\ce{pH}$ of this solution. Assume, 1 mole of each was added to $1L$ solution of water. My ...
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2answers
59 views

What is the minimum pressure for existence of a liquid solution?

The minimum pressure for the existence of liquid solution is (1) $0.6\; atm$ (2) $0.8\; atm$ (3) $0.77\; atm$ (4) $0.9\; atm$ Although this seems to be an informative ...
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108 views

Why is the equilibrium constant wrong for this Gibbs free energy problem?

Solid $\ce{NaHCO3}$ is heated to 90°C. At equilibrium the total pressure of the gases produced is 0.545 atm. Calculate $\ce{ΔG°}$ at 90°C for the reaction $\ce{2 NaHCO3(s) ⇌ Na2CO3(s) + H2O(g) + ...
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38 views

How elements are found to be in their elemental form?

I recently was in need of Zinc for an experiment. So I resorted to obtain it from some dry cell. But I womdered if it was pure Zinc or was it ZnO2 or anyother compoumd of Zn. It then occured to me ...
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91 views

Enthalpy changes (comparing methods)

I learnt that given a reaction $A \to B$, the enthalpy change is given by, $$\Delta H = \left( \begin{array}{c} \text{total enthalpy of}\\ \text{bonds broken}\end{array}\right)-\left( ...
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36 views

Calculate mass percent of water using tritium

1 curie of radiation is equal to 3.7 x 10^10 decay events per second (the number of decay events from 1 g radium in 1 s). A 1.7-mL sample of water containing tritium was injected into a 170-lb ...
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28 views

Remove purple dye from One Shot Drain Cleaner

I bought one shot drain cleaner as a cheap and easily obtainable source of sulphuric acid. However it has an annoying purple dye added to it and I was wondering how to safely remove that without ...
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42 views

Delta G at Equlibrium

Been trying to understand this question. Here is my reasoning: 1) True, because T is positive (105 + 273)K while ΔS should obviously be negative because the final entropy is lower than the initial ...
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1answer
36 views

How to calculate the rotational constants for different states from a stick spectrum?

Given a stick spectrum for an unknown diatomic molecule, how do you determine the rotational constants $B_\nu$ for both the excited and ground states given that $$E_{j}=B_{\nu}j(j+1)$$
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Probability of measuring a particle in the ground state: having trouble with the integration

I am working on a problem in the context of an infinite symmetric potential barrier around the origin, with barriers at $x=- \frac{a}{2}$ and $x=\frac{a}{2}$. The wave function is a symmetric ...