Questions tagged [molecules]

An electrically neutral entity consisting of more than one atom (n > 1). Rigorously, a molecule, in which n > 1 must correspond to a depression on the potential energy surface that is deep enough to confine at least one vibrational state. This tag should be applied to question about certain molecules or a class of them.

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7k views

Draw a simplified MO diagram for the pi system of Methyl vinyl ether

My attempt at the answers: i) 2 bond pairs and 2 lone pairs on oxygen atom therefore bond angle of slightly less than 109.5 degrees, around 104 degrees. ii) 120 degrees bond angle therefore sp2 ...
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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 ...
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How do noble gases bond with themselves?

Noble gases have full electron shells, which virtually blocks any other element from bonding with it. However, I've heard about cases where they bond to each other - for example, helium can ...
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Does STED microscopy allow us to see reactions happening on a substrate

This years nobel prize for chemistry went to nanoscopy using STED as a control mechanism. I have seen the atoms/molecules of a lattice vibrating as shown by Stefan W Hell in a presentation at some ...
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20k views

Stereo Isomerism - syn/anti

I was studying the types of stereo-isomerism E-Z, Cis-Trans and then I come across syn-anti stereo-isomerism this one is giving me a bit of fight in understanding, especially where lone pairs are ...
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Proper typography of “NOx”

I am a journal typesetter, and recently I came to a problem that I'm not sure I know to solve. The question is how to properly typeset the "NOx" abbreviation for nitrogen oxides. Which is ...
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Why is water transparent?

Some substances like copper sulfate for example have vivid colors. But why is water transparent? Does it not emit any visual light from the electromagnetic spectrum?
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838 views

How would you find the mass in grams, if you only know the number of particles of a portion of the formula? [closed]

If you were given a question like below: What is the mass in grams of a sample of $\ce{Fe2(SO4)3}$ that contains $3.59 \times 10^{23}$ sulfate ions, $\ce{SO4^{2−}}$ ? The molar mass of $\ce{Fe2(...
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820 views

Definition of relative atomic mass

I found out there are two definitions of relative atomic mass $A_\mathrm r$. First definition is $A_\mathrm r$ is the mass of 1 atom of an element relative to 1/12 the mass of carbon-12 atom. It can ...
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Chemical composition of petrol

What is the chemical composition of petrol? What are the molecular available in petrol? Some time which is marked with 95% octane. So what is the remain element occupied 5%?
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Molecular Orbital Theory and No. of bonds

The order of filling of molecular orbitals $\ce{O2}$ by MOT is this : But from it, how can I deduce that there is one sigma and one pi bond in an oxygen molecule ?
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367 views

How can we confirm the number of protons in an atom?

The periodic table tells us that there are 6 protons in a carbon atom. Is there a way to verify this first-hand? Or are we just expected to believe it unquestioned?
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Are difluorine and hydrogen chloride considered isoelectronic?

Why are $\ce{F2}$ and $\ce{HCl}$ not considered isoelectronic? Both have 18 electrons. $\begin{align} \ce {H}\!:&\ \ce{1 e-}\\ \ce{Cl}\!:&\ \ce{17 e-}\\ \ce{F}\!:&\ \ce{9 e-}\\ \end{...
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What holds atoms together? [duplicate]

I know atoms are held together by Ionic and Covalent bonds and i understand the ionically bonded atoms are held together by electrostatic forces. What about covalent bonds? How are molecules of bonded ...
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851 views

Converting from Grams to Molecules

I was doing some problems from the textbook on converting between units using dimensional analysis and I came across this problem. A vat of Hydrogen Peroxide ($\ce{H2O2}$) contains 455 grams of ...
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891 views

Establish the formula of an oxide of chromium

An oxide of chromium used in chrome plating has a formula mass of 100.0 u and contains four atoms per formula unit. Establish the formula of this compound, with a minimum of calculation. ...
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What actually is the Wavefunction?

I am aware that the square of the Wavefunction gives the probability density of finding an electron at a particular point in space. I have also heard that it's a complex number but since it's a ...
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Find the partial pressure in a container

I have an air mass which consists of 78.1% $\ce{N_2}$, 20.9% $\ce{O_2}$, 0.964% $\ce{Ar}$, and 0.0378% $\ce{CO_2}$ in a container which volume $\mathrm{V=40~L}$ at a temperature $\mathrm {T = 298.15~K}...
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Electrolysis of Beer

Electrolysis of water, means that the water is separated into hydrogen and oxygen. As beer also includes water, I initially thought electrolysis of beer would cause the water to separate, and the ...
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Can you calculate the properties of a substance based solely on its atomic properties?

I'm trying to write some software that I can use to determine, roughly, what the physical properties of a pure substance are. I know I could just use a database of the known properties of each element,...
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Chemical nomenclature of ions

I'm a very beginner in chemistry. The book I'm studying says that an ion is an atom, or a collection of atoms, that has an electric charge, then it writes about the difference between molecules and ...
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Why does water break salt really

A kid asked me this question just the other day, and I said that the positive part of $\ce{H2O}$ attracts the negative $\ce{Cl}$ ion and the negative part of the $\ce{H2O}$ attracts the positive Na ...
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About the way chemicals and molecules are represented

The standard way of representing molecules with letters like $\ce{C}$ for Carbon, $\ce{O}$ for Oxygen etc.; and a lot of lines and double lines like a graph from Graph theory where each letter is a '...
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Phenyl vs phenol functional group?

Phenyl is a functional group with an aromatic ring bonded to another group. And, phenol is a molecule that is just a phenyl bonded to a hydroxyl group. However, some sources consider phenol itself a ...
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Nitrogen dioxide dimerization

$\ce{NO}$ can't dimerize and that is explained because the free electron is in an antibonding orbital. The same is true for $\ce{NO2}$, but it can dimerize, how?
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How to find out oxidation state when compound has multiple electronegativities

How do I solve for oxidation state in something like CH3-O-F? The fluorine is more electronegative than the oxygen which is more electronegative than the carbon which is more electronegative than the ...
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Why are least electronegative elements usually in center of lewis structure

Many sources state that one of the primary rules for molecular structures is that the least electronegative element is in the center. However, none of them explain why this is the case. Is this ...
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Why is it O-Cl-O and not O-O-Cl?

I'm currently preparing my exam and while I did never think about this question during the course, it begins to confuse me right now... Why is it the structure of $\ce {ClO_{2}-}$ like $\ce {O-Cl-O}$ ...
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What are the fumes that form above liquid nitrogen?

What is the composition of liquid nitrogen fumes? Is direct contact with these fumes harmful?
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Molecules that get charged in Water

I am a chemistry super noob and I was watching a MIT video where the professor states that: "Certain molecules become charged when they come in contact with water in the natural state" Can someone ...
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1answer
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Difference between torsion, out of plane, coplanar and perpendicular bends?

In Infrared spectroscopy, stretches are easily understandable. But, how do I visualize (or conceptually understand) the difference between dihedral (torsions), out of plane bends, coplanar bends, and ...
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Invariants in chemistry used for model selection

What invariants related to geometrical structures that describe molecular geometry are used in chemistry? Explanation: Here, Electronic model with highest prediction rate…, one can learn about ...
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IBrF2 - van der Waals repulsions - and number of unique bond angles

I understand that the molecule $\ce{IBrF2}$ is T-shaped, with three ligand atoms and two non-bonding pairs. However, how many unique bond angles can this molecule exhibit? My professor argues for ...
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854 views

Greater entropy: an atom or macromolecule?

A question that appeared on my last chemistry exam was : Which of the following has greater entropy A) An atom B) A macromolecule The question doesn't specify anything else(i.e. type/size of ...
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Oxidation numbers of phosphorus pentachloride

I read detailed explanations of what oxidation numbers/ states represent and it boils down simply to this: If it's positive, it shows how many electrons the element lost, and in the case of a negative ...
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1answer
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What is molecular system in general terms? What is a supramolecular system?

What is a molecular system in general terms? Could the solution of sugar in water be called a molecular system, if we were not interested in sugar-water interaction? Today Jean Marie Lehn told me ...
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1answer
701 views

How can a chemical structure be stored in a matrix?

How do I represent a chemical structure in a matrix format in Matlab? Can I input a chemical structure into Matlab using the S.M.I.L.E.S notation? I have to specify the connectivity of different ...
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What does 'organic/non-organic molecule' means exactly? [duplicate]

I am new to the organic chemistry world. I was delving for the exact answer to my question, and I've found some results: In wikipedia (french), is was mentioned that an organic molecule contains ...
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1answer
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How does the pyramidalization effect the bonding angles in a distorted octahedral environment?

This is a follow up on "Generally Octahedral - Meaning?". Since Dissenter asked in the comments to my answer: I'm not sure why the $\ce{F_{eq}-S-F'_{eq}}$ bond angles would be compressed, even if ...
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276 views

Molecular orbitals and “generalized” aufbau principle for heteronuclear molecular configurations

Is there any general ordering or rule for heteronuclear molecules like $\ce{AX_2}$, $\ce{AX_{n}}$, and their molecular bonding/antibonding configurations ($\sigma/\pi$ orbitals) accordingly to some ...
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Relationship between Van der Waals forces and the boiling point

Choose the right answers in the following statement: The boiling point of a liquid substance is higher as the Van der Waals forces (in/between) the molecules of the substance are (lower/higher). I ...
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154 views

Existence of Hyponitrite Molecule

Does the hyponitrite molecule exist? I know the hyponitrite ion exists (http://en.wikipedia.org/wiki/Hyponitrite) but what about the molecule? I have found no reference to the molecular form on ...
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207 views

In which of the following chemical compounds are the building blocks molecules?

In which of the following chemical compounds are the building blocks molecules? (A) $\ce{AgNO3}$ (B) $\ce{HNO3}$ (C) $\ce{KNO3}$ (D) $\ce{NaNO3}$ (B) is the correct answer, but I have ...
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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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Fractional Bond Order - How to Visualize?

Consider nitric oxide, which has a real bond order of 2.5, contrary to what this UC Davis rendering might imply: What's the best way to visualize a molecule with a fractional bond order? What exactly ...
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What is there in this 3D representation of organic molecules I fail to grasp?

I think there's a basic idea I'm missing about 3 Dimensional representation of molecules. I think it may be about converting to Fischer representation. Consider the following two products of ...
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How can we rationalise the amount of crystal water in coordination complexes?

I was wondering why specific number of water molecules are attached to salts like $\ce{CuSO4.5H2O}$? Searching gave me a satisfying picture : I think $\ce{FeSO4.7H2O}$ should have a similar ...
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Calculating the mass in g of a molecule [closed]

If I have the amount of the molecule in moles, how do I calculate the mass of an individual molecule? For example, if the molecule was water?
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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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How to explain the concept of mol and reactions involving mol quantities

From time to time I do little pro bono lessons for second grade in math, physics, and chemistry. Recently I came across this question. In a container is $2~\mathrm{mol}$ of $\ce{SO3}$ (sulfur ...