Questions tagged [hydrogen]

Questions regarding the chemical properties of hydrogen and its behavior in reactions and compounds.

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37
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6answers
62k views

Why do we use helium in balloons?

While I was looking at the periodic table today, I realised that there were gases that were much lighter than helium such as hydrogen. If hydrogen is lighter than helium, why do we insist on using ...
31
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1answer
10k views

Why are there two Hydrogen atoms on some periodic tables?

Most periodic tables only feature one Hydrogen atom, on the top of the first group. But some, like the one I was given, also show Hydrogen in the 7th group, to left of Helium. Why are there two ...
30
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3answers
5k views

Why are isotopes of hydrogen the only ones with special names?

Why does no other element but hydrogen get special names for its isotopes?
28
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1answer
546 views

How does Palladium dissociate H₂ so easily?

If I understand correctly, $\ce{H2}$ in the presence of $\ce{Pd}$ readily dissociates as it dissolves into the metal. With the dissociation energy for the $\ce{H—H}$ bond being so large, how is this ...
26
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3answers
25k views

Why can't Pd/C and H2 reduce both the alkene and carbonyl portions of α,β-unsaturated carbonyls?

Why is it that the major product of the reduction of chalcones the ketone and not the monoalcohol? In other words, Why isn't the major product a benzyl alcohol? From what I understand, catalytic ...
21
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5answers
15k views

Is there such a thing as an acid without a hydrogen?

I'm in AP Chemistry and we are learning about the Brønsted-Lowry model and my teacher mentioned that "for the most part" acids have hydrogen, could there be such a thing as an acid that has no ...
21
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1answer
3k views

Why are hydrogen ions always associated with another molecule?

I was reading N.C.E.R.T. class XI part 2 book and chapter Hydrogen,when I came across this statement: Loss of the electron from hydrogen atom results in nucleus ($\ce{H+}$) of ~1.510–3 pm size. ...
17
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4answers
98k views

Why are there multiple lines in the hydrogen line spectrum?

Hydrogen has only one electron, yet it exhibits multiple lines in a spectral series, why is this?
15
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4answers
52k views

Why is formic acid a stronger acid than acetic acid?

I am told that because the methyl group is electron donating in the conjugate base of acetic acid, this destabilizes the conjugate base by exacerbating the existing negative formal charge on the ...
15
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1answer
642 views

Are there any examples of nuclear spin isomers having consequences for chemical reactivity?

Ortho- and parahydrogen are two forms of the $\ce{H2}$ molecule that are distinguished by their pairing or antipairing of nuclear spins, giving rise to metastable singlet (ortho-) and triplet (para-) ...
15
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1answer
248 views

Photoionisation microscopy of hydrogen - where are the p orbitals?

In this Physics Review Letters article, which was published in 2013, but I found recently, the authors report photoionisation microscopy images of hydrogen atoms in various electronic states. A. S....
14
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4answers
27k views

How explosive is hydrogen gas?

I want to electrolyze water to get oxygen and hydrogen. I want to mix them in a regular balloon and ignite it. How much hydrogen would you need in a 2:1 ratio with air for it to be dangerous? Is this ...
14
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1answer
11k views

If electrolysis splits water, why does only either hydrogen or oxygen (but not both) bubble up on one pole?

If electrolysis splits water, then that means that $\ce{H2O}$ is split into $\ce{H}$ and $\ce{OH}$ or $\ce{O}$. How come that if a water molecule is split at e.g. the negative pole (anode), only the ...
14
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3answers
3k views

Reaction mechanism of combustion of hydrogen

After a discussion about the usefulness of hydrogen fuel for cars with a friend of mine, I wondered what the reaction mechanism for combustion of $\ce{H2}$ was. I only study (well almost) organic ...
14
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2answers
888 views

What bond exists in “red oxygen”, and can something similar happen with hydrogen?

"Red oxygen" is the nickname for O$_8$. It only exists at extremely high pressures. What kind of bond does it have? Can hydrogen theoretically have something similar at very high pressures too?
14
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1answer
856 views

Are there any significant uses of the compound formed by magnesium and anthracene?

In an unusual reaction, magnesium reacts with anthracene in THF to form a grignard-like compound called, prosaically, magnesium anthracene: I remember using it briefly in the 1980s. At the time there ...
13
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4answers
25k views

Which orbitals of the hydrogen atom are degenerate for n=3?

Which of the following orbitals are degenerate in the hydrogen atom with $n = 3$? A. II and III only; B. I and IV only; C. I, II, and IV only; D. II, III, and IV only; E. all. The ...
12
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2answers
3k views

Would sodium explode in salt water?

I’ve seen the video etc of sodium being put into freshwater and the reaction of flames/small explosion but I wonder if the same reaction would occur if conducted in salt water such as the ocean.
12
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3answers
2k views

On the stability of deuterium

The isotope of hydrogen, tritium, is indeed radioactive resulting in $\ce{^3He}$ through beta decay. But what of the radioactively 'stable' isotope deuterium? Are all deuterium atoms destined to be ...
12
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1answer
3k views

Why are some elements more abundant than others in the universe?

Hydrogen is the most abundant element in the universe. But what makes it so? At the time of big bang, what made certain elements more abundant than the others? I don't find this order of abundance ...
12
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3answers
4k views

Difference between Lindlar and Rosenmund catalysts

Is there any difference between the Lindlar and Rosenmund catalysts? I've checked around, and it seems the same compounds are used to make both. Is there a difference in their reactivities or are they ...
12
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2answers
1k views

Why is slush hydrogen at the triple point?

Slush hydrogen is a mixture of liquid and solid hydrogen at the triple point considered as a possible vehicle fuel. What is the need of having it at the triple point? Couldn't any other set of ...
12
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0answers
181 views

Densest hydrogen storage medium [closed]

What compounds or nanostructures contain the most hydrogen atoms per unit of volume in realistic conditions (under 1 GPa). Particularly boron-free compounds because it's to be used in sci-fi nuclear ...
11
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2answers
4k views

What is the difference between “atomic hydrogen” and “nascent hydrogen”?

My book (Comprehensive Chemistry by Dr. N . K. Verma, S. K. Khanna, Dr. B. Kapila) mentions two forms of hydrogen — "atomic" & "nascent". It says that these two forms of hydrogen are more ...
11
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1answer
855 views

Chemical equation that can be balanced in infinite number of ways?

When I was studying for my chemistry test, I found an equation that illustrates how to get water gas (carbon monoxide + hydrogen) out of methane. It is stated like this: $$\begin{align}\ce{2CH4 + CO2 +...
11
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1answer
3k views

Why are so many wave functions associated with hydrogen?

According to Wikipedia, there's an infinite set of possible wavefunctions (orbitals) for the hydrogen atom: $$\psi_{n\ell m}(r,\theta,\phi) = \sqrt {{\left ( \frac{2}{n a_0} \right )}^3\frac{(n-\ell-...
10
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1answer
4k views

Can 1 mole of H2 react partially with one mole of O2?

I am currently studying stoichiometry (high school level) and we came across the following equation in school: $\ce{2H2 + 1O2 -> 2H2O}$ which is clear to me. We learned in school that reactions ...
10
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1answer
437 views

Hydrogen's confusing purple glow

While reading about hydrogen on Wikipedia, I read that hydrogen has a purple glow in its plasma state. This confused me because although hydrogen is present in its plasma state on the sun, the sun ...
10
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1answer
1k views

Does hydrogen react with air at room temperature and pressure?

I have a container with 3% hydrogen and the rest is air. How fast will the hydrogen get oxidized by air? How much will the reaction speed up with increased temperature?
9
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1answer
2k views

What is the bonding type in hydrides of group 2 elements?

In one of my MCQ questions, there was a statement saying all group 2 elements form covalent hydroxides. I know it is incorrect. I know that $\ce{BeH2}$ is a covalent hydride. What about the rest? Are ...
8
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2answers
8k views

Why is there a need of polar coordinates to solve the Schrödinger wave equation for the hydrogen atom?

Why is there a need of polar coordinate to solve the Schrödinger wave equation for the hydrogen atom? I went through some standard text books but I am feeling rather confused about the explanation.
8
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1answer
2k views

Does the hydrogen ion actually exist? [duplicate]

A chemistry test I did was an IGCSE test. One of the questions was Is Hydrogen Chloride ionic or covalent? Now, on a sheet I have been given, it states the hydrogen ion is $\ce{H+}$. So, it forms ...
8
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3answers
870 views

How to add hydrogens to a crystal structure?

PDB protein crystal structures most of the time lack hydrogen atoms. Usually I use PyMOL (h_add) but it does not always seem to be giving the correct result. What ...
8
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2answers
2k views

Is real water made up of heavy water and light water?

I need to know, is real water made up of heavy water which is formed with deuterium, and light water which is water by protium? We know that hydrogen has three major isotopes, including protium and ...
8
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1answer
1k views

Why do spin isomers of hydrogen (ortho and para hydrogen) change their nuclear spin with temperature variance?

My book says that ordinary dihydrogen contains 75% ortho and 25% para forms of hydrogen, while at significantly lower temperatures (like 20K) ortho and para hydrogens are 0.18% and 99.82% respectively....
8
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2answers
507 views

Oxidation state of hydrogen in the LaNi5H intermetallic

This question is from an introductory chemistry course: What is the oxidation state of $\ce{H}$ in $\ce{NaH}$, $\ce{HCl}$, and $\ce{LaNi5H}$? I've looked in the textbook to no avail. Google ...
8
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1answer
110 views

Does the hydrohelium dication exist?

It is well-known that there exists the $\ce{He2^2+}$ dication, and also $\ce{HHe+}$ and $\ce{H2+}$ cations. But I could not find any definite information about the existence or inexistence of the $\ce{...
8
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2answers
357 views

Reliable automatic addition of hydrogens and charge assignment to small molecules at given pH?

I have some PDB structures of small molecules with missing hydrogens. Is there a software available that places missing hydrogens and assigns a charge to the molecule that is reliable? I am looking ...
8
votes
1answer
427 views

Why isn't pure ortho hydrogen possible to obtain?

In school, I've learned that we can only get an ortho hydrogen content upto 75%. Why is that we can obtain a pure sample of para hydrogen, but not ortho hydrogen? What prevents us from isolating ortho ...
8
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1answer
6k views

Relationship between surface area of electrode and reaction rate of hydrogen in fuel cells

I am looking at the effects of increasing the surface area of which the flowing hydrogen fuel is in contact with the anode in a fuel cell. At the anode the hydrogen is catalytically split into ...
8
votes
2answers
13k views

Rate and mechanism of the reaction of Mg and HCl

In the reaction between hydrochloric acid and Magnesium the overall reaction is: $$\ce{Mg + 2HCl -> MgCl2 + H2}$$ My proposed mechanism of reaction is that $\ce{HCl}$ dissociates in $\ce{H2O}$ ...
8
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1answer
173 views

Why would the loss of H₂ to space mean that the Earth's geochemistry would be based on acid/base reactions?

I am reading a paper[1] that contains the line: Most of the $\ce{H2}$ in the Earth's mantle escaped to space early in the Earth's history; consequently, the overwhelming majority of the abiotic ...
7
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2answers
4k views

Why is there no neutron in protium?

My chemistry teacher once told me, that every atom should have at least as many neutrons as protons, to keep the electrons from crashing into the nucleus. Protium, however, doesn't even have ...
7
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2answers
6k views

What is difference between H⁺ and proton?

What is difference between $\ce{H+}$ and a proton?
7
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1answer
2k views

Is there a reaction to get hydrogen from hydrocarbons?

Combustion of hydrocarbons reveals hydrogen, but not sure at what efficiency. Is there a reaction to get hydrogen from hydrocarbons?
7
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2answers
1k views

Really how rare are hydrogen atoms?

Hasok Chang, a chemist, but perhaps more a philosopher recently published the book Is Water H2O? . Chang used the question and an extensive web of arguments ultimately as a platform to support a ...
7
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1answer
127 views

Why do we need to add hydrogen to amorphous silicon?

I was recently studying about Staebler-Wronski effect observed in amorphous silicon (a-Si). I realised it was due to imperfections in the lattice structure and breaking of Si-Si bond to Si-H bonds. ...
7
votes
2answers
5k views

Why are hydrogenation reactions exothermic?

I learned that all reactions that yield hydrogen are endothermic (such has reforming) and reactions that use up hydrogen are exothermic (FCC cracking, hydrogenation, etc.). But why is this so? I know ...
7
votes
1answer
2k views

Why is the electronegativity of hydrogen 2.20?

Well, I was doing research about the ways we can measure electronegativity and I just realized there must be an arbitrary electronegativity set for an specific element to give us the relative amounts ...
7
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1answer
2k views

Specific Heat Capacity of Heavy Water

Water has an unusually high specific heat capacity due to it's hydrogen bonds. Why is it that the change in isotope causes a 10% difference in the heat capacity? How does the added neutron in the ...