All Questions

40,145 questions
Filter by
Sorted by
Tagged with
4 views

isotopologue distribution, difference among CID (carbon isotopologue distribution) and MID

I am new into LC-MS/MS stable isotope targeted downstream analysis. I've found numerous papers talking about MID (Mass isotopomer distribution) but in some european publications I found CID (carbon ...
26 views

Why isn't change in Gibbs free energy always zero for isothermal and isobaric chemical reactions?

$G = H - TS$ $=> dG = dU + pdV + Vdp - TdS - SdT$ At constant pressure and temperature (which is the condition for most chemical reactions) we have $dG = pdV - Tds$ Now, $dq = dU + dW$ ( first law ...
31 views

Where does the energy from combustion come from?

I am aware that combustion reactions are exothermic. The energy stored in the chemical bonds of the products is less than the energy stored in the chemical bonds of the reactants. The difference in ...
22 views

Entropy change in a vacuum?

What is the total entropy change of an ideal gas undergoing an adiabatic expansion in a vacuum? It is my understanding that since the expansion is adiabatic, there is no change in entropy change ...
25 views

number notation with space in atomic mass

I'm self-educating myself in the periodic table and came across some number notations I am not familiar with. Also to clarify, I have no school background and English is not my native language. That ...
The simple mechanical application of the electron hole operator to sulfate radical anion suggests but two possible reactions (if energetically possible), of which one is: $\ce { •SO4– + h+ = SO3 + O ... 0answers 29 views Is lead vapor toxic? Is evaporative lead toxic if it condenses as dust? I've heard that elemental lead and lead oxide are inert. I know that lead compounds and salts are poisonous. If lead is boiled, are the vapors toxic or small particles toxic when condensed? 0answers 19 views Combustion Temperature Calculation Using C_p and Heat of Formation I am simulating the combustion temperature for various compositions of syngas and finding the product temperature. Part one is varying the ratio of CO and H2 from 3:1 to 1:3 in the syngas, burning it ... 2answers 44 views Can a gas expand and change its volume at STP by doing work on its surrounding? I came across this question: 1 g of H2 gas expands at STP to occupy double of its original volume. The work done during the process is? So can a gas expand and change its volume at STP by doing work ... 0answers 35 views Can 5% sulfuric acid and 3% hydrogen peroxide form piranha solution? I'd like to use 5% sulfuric acid and 3% hydrogen peroxide as an etching solution for copper. (In the past I've used dilute hydrochloric acid and hydrogen peroxide but the generation of chlorine gas ... 0answers 21 views States of Matter [closed] Why do some heavy molecules exist as gases at a certain temperature, when lighter molecules are solids or liquids at that temperature? I am asking because radon is normally a gas, but that it has a ... 0answers 26 views CuCO3 ---> CuO + CO2 [duplicate] When we add heat to CuCO3, we have a decomposition reaction of CuCO3 ---> CuO + CO2. Why is this so? Why does it decompose into CuO and CO2? I read that this has to do with polarization. Please ... 0answers 14 views Can large, sticky, sodium polyacrylate crystals be coated in a powder to facilitate handling? I am separating a larger container of sodium polyacrylate crystals into smaller containers for student experiments. Commonly known as "Deco Cubes" and used by florists in decorations and ... 0answers 54 views Why do papads make sound when touched with wet hands? When I was eating papads (well-toasted crispy doughs/chips served in various regions of India and Nepal) I found that touching them with my wet hand made them make quiet yet audible crackling sound. ... 0answers 14 views Handling of tautomerism in QSAR modelling This article from 2009: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2776169/ mentions the potential impact of tautomerism on QSAR modelling, and concludes that more work is needed to address it. 12 ... 0answers 18 views Amino acid charge I have a ween problem with amino acids (AA). Everywhere I look are AA written with NH2 and COOH group, but why? pK of these groups are (at neutral pH = 7) for NH2 group lower and for COOH group higher ... 0answers 27 views maximum no of atoms in a plane including and excluding central atom in C(CN) 4 [closed] Options A) 6&6 B) 6&5 C) 5&6 D) 5&4 According to me exclusive of central atom there are 6 atoms in a plane 0answers 24 views What is the number of the orbitals which are completely filled with electrons in an element whose atomic number is 16? All my knowledge To solve this answer you have to do electronic configuration of an atom whose atomic number is 16 , so the electronic configuration will be = 1s^2, 2s^2 ,2p^6 ,3s^2 ,3p^4 , what I ... 1answer 45 views Why are the relative masses of isotopes not close to whole numbers? Understandably, the relative atomic masses of isotopes are often not close to whole numbers as they're adjusted for isotope abudandancy eg.$A_r(Cl)\approx35.45$. However, wouldn't one expect the ... 0answers 10 views Where to find DNA structural atomic coordinates? [migrated] I need a code/app/website that can receive a DNA sequence, for instance AATCT, and output a file with the atomic coordinates. I used to do this on this website http://www.scfbio-iitd.res.in/software/... 2answers 45 views Can you coat/ "plate" things with non metals or compounds? [closed] I was recently watching a video on electro plating I understand that it only works with metals so I wondered if there's a method to do the same thing but with non-metals. 0answers 14 views Bromine Clock reaction Why doesn't the bromine react with the methyl red at the start of the bromine clock reaction? I assume the rate of reaction (and rapid removal) of bromine with phenol is much, much, much faster than ... 0answers 18 views Is the following carbanion intermediate anti aromatic? [closed] The following carbanion has 20 pi electrons . Shouldn't it be anti aromatic ? 0answers 32 views Is shampoo or soap a better emulsifier? Made homemade shampoo using: Sodium lauryl sulfate (SLS) Glycerin 95% ethanol Sodium stearate Made homemade soap using: 20% sodium hydroxide Vegetable oil 95% ethanol 20% sodium chloride ... 0answers 25 views Wave Dispersive X-ray Fluoresence and Bragg's Law Thermo Fisher website explains that "WDXRF uses crystals to disperse the fluorescence spectrum into individual wavelengths of each element, providing high resolution and low background spectra ... 0answers 34 views How Quantum codes calculate the electron density? I'm a newbie student in theoretical chemistry, and i just start to learn to basics in this field, and I always encounter a bunch of concepts like Hartree-Fock (HF), Electron Density, DFT. I managed to ... 0answers 47 views Microscopically, how does temperature increases in simple exothermic reactions? [duplicate] Let’s say we have a simple exothermic reaction$\ce{A_{(g)} + B_{(g)} -> C_{(g)}}$Since it’s exothermic, that means that kinetic energy of C is greater than the kinetic energy of the reagents. ... 1answer 36 views Reversible and Irreversible processes In an ideal world, is moving a piston quickly, a reversible process as there is no heat loss due to friction? (as opposed to a quasi static process) 0answers 33 views What is change in enthalpy in energy profile? [closed] Consider an energy profile diagram. My doubt is that why does change in potential energy (PE) equal change in enthalpy here? At constant pressure change in enthalpy equals the net heat exchanged ... 0answers 25 views What is meant by "charge separation" for resonance structures? [duplicate] I'm confused about the definition of "charge separation" in the context of resonance structures. One of the rules of stability of resonance structure is "the structure with least ... 0answers 22 views How to make equimolar solution of 72٪ (12)؜ sulfuric acid and 99% Triehylamine (TEA) [closed] I need to mix TEA and H2SO4 in equimmolar ratio. Acid is 72% pure and TEA is 99% pure.Both in liquid form. What should be the mass of each liquids? Further can I increase the purity of both liquids ... 0answers 53 views Is this plastic clip made of polypropylene or polyethylene? I am trying to re-attach an automotive clip (painted plastic with a yellow (epoxy?) hard adhesive backing) which secures a trim piece back onto the vehicle's roof sheet metal (unpainted (primed?) area)... 0answers 53 views What do we define as "surroundings" in thermodynamics? [duplicate] I was thinking about the 2nd law of thermodynamics, and how ΔStotal=ΔSsystem+ΔSsurrounding. You could potentially have a reaction with negative ΔStotal occurring- a non-spontaneous reaction. But by ... 1answer 80 views Why is it difficult to calculate ΔS of the surroundings (said a teacher)? My chemistry teacher told me that the Gibbs Free Energy (G) function was created because determination of ΔSsurroundings, and thus ΔStotal was difficult, and we needed something better to explain ... 0answers 30 views Olivetolic acid synthesis I have both Malonyl - CoA and Hexanoic Acid at my disposal. There is very little information on the SYNTHETIC process of olivetol acid. From my understanding, you must first convert the two CoA's into ... 0answers 31 views Do we need to consider hydrogen bonding in organic molecules before deprotonation for comparison of acidic strenghts? Let's suppose in this question hydrogen bonding would be considered in structure 3 ... if yes, then it would be a weak acid because it will not donate H+, but according to the answer given in the book ... 0answers 30 views Modeling chemical reaction [closed] Can someone please tell me how do model chemical reactions, by this I mean prepare input of chemicals on LHS and RHS of the equation. I can see how input CO2 can be prepared and for H+, I think for ... 0answers 48 views Retrosynthesis of {6-[2-(benzylamino)ethyl]-1,4-dihydropyrimidin-4-yl}methanol I have {6-[2-(benzylamino)ethyl]-1,4-dihydropyrimidin-4-yl}methanol (at the top) and have to make the retrosynthesis steps for my class. I tried different things but I'm not sure about it. In 1 you ... 0answers 24 views What is the exact definition for isoelectronic species? [closed] Suppose, I have two ions with the same number of electrons, but their electronic configuration differs slightly from eachother. Then, will they be called isoelectronic? 1answer 52 views Relationship between the principal axes of inertia of an enantiomeric pair If an object is chiral, itself and its mirror image are non-superimposable and represent two distinct version of the same object. A hand, for instance, can be either the right hand or the left hand. ... 1answer 32 views Do ferrofluid nanoparticles come out of solution when exposed to a solenoid DC field current? As the electrically-charged ionic tails of surfactants used to attach to the magnetic nanoparticles require the particle to be magnetized to stick to them; if a ferrofluid is passed has a solenoid DC ... 0answers 46 views How to make a Lithium Ion Cell? [closed] LiNiCoMnO2 This video shows the opening of Lithium Ion battery at https://www.youtube.com/watch?v=-KAHiCb_8-s Question 1: Can LiNiCoMnO2 powder be made from melting Li,Ni,Co,Mn together at high ... 1answer 43 views Why are anti bonding orbitals distorted towards the less electronegative element? Bonding molecular orbitals are distorted towards the more electronegative atom and so the atomic orbitals from this atom contribute more to those bonding orbitals. This implies that anti bonding ... 1answer 74 views Has anyone added dyes to a mixture about to separated by chromatography in order to visualize where the desired product lies? Usually in preparative chromatography one needs to know when the desired substance to be separated is coming down the pike. Often this required some sophisticated instrumentation. But, it occurred to ... 0answers 44 views Mass spec mass calculation difference This is not a homework question, but for research. I am performing mass spec on serum metabolites using Thermo Q Exactive PLUS with a HESI source which was set to a spray voltage of -2.7kV under ... 1answer 28 views Removing bugs and tar from my car with Bounce fabric softener sheets I just used Bounce fabric softener moistened with water to remove stuck tar and dried bugs from my car. It worked like a charm, wiping it clean in seconds. Why did this work? The web says it ... 1answer 35 views Reactivity of Alkenes with HBr [closed] I am new in the Organic Chemistry (World of Reactions). I had got one question in my test. But, when I had seen it, I got no proper logic to tick the correct answer, and then when I saw solution, then ... 1answer 267 views What are the safest non-toxic elements I can own? [closed] As in a recent question, I mentioned I collect elements. My collection already has quite a few elements and a rare alloy (I have silicon, molybdenum, tungsten, gold, platinum, silver, copper, ... 0answers 31 views How would I find what specific wavelength I need to measure for a specific chemical in spectrophotometry (calcium perchlorate)? I am currently doing a research project, and for it, I would like to use a photospectrometer to find the concentration of Calcium Perchlorate in my sample solutions. My current method of data ... 1answer 92 views Bond-order parameter$g_6(r)\$
I would like to know the explicit steps to compute the bond correlation function $$g_6(r) = \langle\Psi_6^*(0) \cdot \Psi_6(r)\rangle$$ for colloids in my experiment (2D). I have the position of all ...