60 votes
Accepted

Why do we use helium in balloons?

As other answers have noted, the only gas lighter than helium is hydrogen, which has some flammability issues that make it more difficult to handle safely than helium. Also, in practice, hydrogen is ...
49 votes

Why do we use helium in balloons?

Actually, hydrogen is the only gas that is lighter than helium. However, it has a very big disadvantage: It is highly flammable. On the other hand, helium is almost completely inert - this is why it ...
35 votes
Accepted

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

It depends on which definition of acids and bases you are using. According to the Arrhenius theory, acids are defined as a compound or element that releases hydrogen (H+) ions into the solution. ...
31 votes
Accepted

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

Harold Urey and George Murphy used spectroscopy to identify deuterium late in 1931, announcing it at the 1931 Christmas meeting of the American Physical Society. Picking up out of 'From Nuclear ...
  • 7,709
27 votes

Why does hydrogen burn with a pale blue flame while its emission spectral lines are red in colour?

It is a very interesting question, but comparing a combustion spectrum with an atomic emission one is like comparing apples and oranges. A flame is a luminous gas phase chemical reaction where the ...
  • 33.7k
26 votes
Accepted

Why is formic acid a stronger acid than acetic acid?

We are discussing the following equilibrium We can make the acid a stronger acid by pushing the equilibrium to the right. To push the equilibrium to the right we can destabilize the starting acid ...
  • 82.5k
26 votes

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

In addition to the reasons ste listed, the isotopes of hydrogen have the greatest differences in mass compared to other elements. Consider that deuterium is twice as heavy as protium, and tritium is ...
  • 10.5k
26 votes
Accepted

At what pressure will hydrogen start to liquefy at room temperature?

$\ce{H2}$ cannot be liquified at room temperature, whatever the pressure. Generally speaking, all gases can only be liquified when the temperature is under its critical value.
  • 22.5k
23 votes

What is difference between H⁺ and proton?

There is no chemical difference, only a psychological one: how do you think about it. They are both the same thing, but many people associate $\ce{H+}$ ions with chemical reactions and protons with ...
  • 7,116
23 votes
Accepted

Is water a possible fuel for jet engines?

It can't work because of the fundamental thermodynamics What you are proposing is, basically, the plane carries water; the water is broken down into its components, hydrogen and oxygen; the ...
  • 32.9k
23 votes

At what pressure will hydrogen start to liquefy at room temperature?

The critical temperature of Hydrogen is $\pu{32.938 K, resp. -240.21 ^{\circ}C}$. Above this temperature, it cannot be liquified. So to answer your question, you can get as high pressure as you can ...
  • 29.7k
22 votes
Accepted

Why are protons more common than hydride ion?

This is because we live in a world dominated by oxygen and water. In other words, it is an oxidized world. Most metals occur naturally in the form of oxides, silicates, halides, or other derivatives. ...
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21 votes
Accepted

Difference between Lindlar and Rosenmund catalysts

This is a rather interesting question because these names actually refer to classes of reactions (specific to certain reagents and products), and aren't constrained by specific proportions of ...
  • 23.5k
21 votes

Would sodium explode in salt water?

Yes, sodium metal is also going to react exothermically with salt water or any other aqueous solution as long as it comes in contact with water: $$\ce{Na (s) + H2O -> Na+ (aq) + OH- (aq) + 0.5 H2 (...
  • 35.7k
19 votes

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

You hit it right on the nose. The real key piece of information is that given enough time, all the unsaturated bonds will be reduced. This tells you that though the reduction is thermodynamically ...
  • 23.5k
18 votes
Accepted

Reaction mechanism of combustion of hydrogen

This post deals with the mechanism that is observed in the gas phase. It is of course not as simple as the equation might suggest and you did suspect that already. $$\ce{2H2 + O2 -> 2H2O}$$ This ...
17 votes
Accepted

Why is there no neutron in protium?

Your chemistry teacher is making a few simplifications there that make the statement false on a black-and-white true-and-false scale. Protons would repel each other electrostaticly due to their same ...
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17 votes
Accepted

What is the difference between "atomic hydrogen" and "nascent hydrogen"?

Is your book by chance very old? From the Wikipedia entry for "nascent hydrogen": Nascent hydrogen is purported to consist of a chemically reactive form of hydrogen that is freshly generated, ...
  • 16.9k
16 votes

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

I think there are two reasons. First, it is more convenient to categorize them under the actual element-name to which they belong. If I say "15-Beryllium" everyone knows immediately, what I'm talking ...
  • 642
16 votes
Accepted

Does the hydrogen ion actually exist?

Yes free $\ce{H+}$ ions, protons, really exist. Protons are constantly emanating from the sun and reaching Earth. The proton flux is continuously monitored by satellite. However, in a ...
  • 39.1k
16 votes
Accepted

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

WHAT MAKES HYDROGEN ABUNDANT IN UNIVERSE: After few minutes of creation of the universe, protons and neutrons began to react with each other to form deuterium, an isotope of hydrogen. Deuterium, soon ...
  • 1,635
15 votes

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

There are quite a number of theories regarding acidity and basicity, but in this case, will explain the Lewis acid. The Lewis Theory of acids and bases This theory extends well beyond the things you ...
15 votes
Accepted

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

It seems like an idea of using magnesium anthracene systems for the $\ce{MgH2}$ production persisted since 1980s [1] till late 2000s, when new more efficient method with better scalability for ...
  • 35.7k
14 votes
Accepted

Why are hydrogen ions always associated with another molecule?

The way I understand it is (and my understanding is by no means perfect, or complete), as you pointed out correctly: a hydrogen ion is in fact a proton. The proton is a "bare charge" and as you ...
  • 8,335
14 votes
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Which gas is a oxidizing agent as well as a reducing agent?

I'm guessing your teacher is looking for sulfur dioxide as the answer, but I don't see how or why you're supposed to be able to arrive to this answer logically. Either you'd need to read about it ...
13 votes
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Can hydrogen peroxide reduce ferric ion to ferrous ion?

You are right. This question is "practically" incorrect, although on paper it might appear so if someone is unaware of real chemistry (the question setter). Iron (II) will readily ...
  • 33.7k
12 votes
Accepted

How is bonding in the trihydrogen cation and triatomic hydrogen possible?

Here are the vital parts from the links about $\ce{H3}$ in the question: The molecule can only exist in an excited state [...] the electronic state for a trihydrogen cation with an electron ...
  • 20.9k
12 votes
Accepted

On the stability of deuterium

No, deuterium is completely stable. I found the answer at Hyperphysics, and it has to do with the mass energies of the products and reactants of this hypothetical reaction. The decay of deuterium ...
12 votes
Accepted

Is there a reaction to get hydrogen from hydrocarbons?

Hydrocarbons are in fact the main source of hydrogen gas. According to Wikipedia, 95% of all hydrogen is produced by the steam reforming reaction: $$\ce{CH4(g) + H2O(g) -> 3H2(g) + CO(g)}$$ This ...
12 votes
Accepted

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

The effect is due to the symmetry properties of the rotational energy levels and those of the nuclear spin. The change with temperature is, as usual, traced back to the Boltzmann distribution. In ...
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