# Is hydrohalic acid volatile?

#### Lifeforbetter

Homework Statement
HCl and HF are volatile
Can i conclude that Hydrohalic Acid group is volatile?
Homework Equations
HCl and HF are amongs Hydrohalic Acid group
HCl and HF are amongs Hydrohalic Acid group

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#### jim mcnamara

Mentor
Volatility is related to boiling point. A bit of google-fu gives me:
Hydroiodic acid BP=127°C
Hydrodbromic acid BP=122°C
Hydrofluoric acid BP=19.5°C

So the answer to your question is? Note that acids like these are normally dissolved in water with 100°C BP. The definition of volatile is 'easily evaporates at normal (circa 20°C) temperatures.'

That means you tell me. :)

Last edited:

#### Lifeforbetter

Volatility is related to boiling point. A bit of google-fu gives me:
Hydroiodic acid BP=127°C
Hydrodbromic acid BP=122°C
Hydrofluoric acid BP=19.5°C

So the answer to your question is? Note that acids like these are normally dissolved in water with 100°C BP. The definition of volatile is 'easily evaporates at normal (circa 20°C) temperatures.'

That means you tell me. :)
Ok it means not all amongs Hydrohalic Acid group is volatile?

Mentor
In a word, yes.

#### Lifeforbetter

In a word, yes.
HCl volatile but BP is 108.58 C?

#### jim mcnamara

Mentor
Partial pressures of vapor above the surface of a liquid.

Volatility is a sort relative term for some resources. What is means is that a solution or a pure compound (sublimate) will go into the gaseous state at room temperature. It is important for human safety when, using these products, as in 'Do I need a fume hood?'

#### Lifeforbetter

Partial pressures of vapor above the surface of a liquid.

Volatility is a sort relative term for some resources. What is means is that a solution or a pure compound (sublimate) will go into the gaseous state at room temperature. It is important for human safety when, using these products, as in 'Do I need a fume hood?'
Is there a rule to differentiate volatile and non volatile solution?

#### Nik_2213

Is there a rule to differentiate volatile and non volatile solution?
Toxicology ? LD50 ?? Accepted exposure limits ? Temperature handling range ??

A hint of HCL isn't so bad, but it will so start eating stuff. Its kin are variously dangerous, especially 'Be NOT There' HF. And I would suggest 'HCN' sorta qualifies as a semi-hydrohalide due to its similar properties...

#### TeethWhitener

Gold Member
Are you asking about hydrogen bromide/iodide (both gases @RT) or hydrobromic/hydriodic acid (the same gases dissolved in water)?

#### Ygggdrasil

Gold Member
Volatility is related to boiling point.
Actually, in this case, the volatility of hydrohalic acids is more related to the equilibrium between aqueous hydrohalic acid and molecular hydrogen halides, which are gasses at room temperature (as noted by @TeethWhitener):

$H^+_{(aq)} + X^-_{(aq)} \rightleftharpoons HX_{(g)}$

So, the volatility will depend a lot on the concentration of halide and pH of the solution. Any saturated solution of hydrohalic acid will be fuming hydrogen halide gas and pose safety hazards. More dilute solutions will give off less gaseous hydrogen halide (despite having a lower boiling point).

#### Lifeforbetter

Someone says most to least volatile HCl<Hbr< HI<HF
HF is volatile
Means all above volatile
All above is hydrohalic acid

#### TeethWhitener

Gold Member
Someone says most to least volatile HCl<Hbr< HI<HF
HF is volatile
Means all above volatile
All above is hydrohalic acid
1) “Someone” is not an acceptable source.
2) The list you give is the hydrogen halides arranged in order of increasing boiling point. All of the hydrogen halides are gases at room temperature. As has been mentioned previously, “volatility” is related to partial pressure. So a liquid at room temperature might still be considered volatile if it has a high vapor pressure.
3) Also mentioned previously, hydrogen halides refer to the free gases. Hydrohalic acid refers to that gas dissolved in water. The concentration of the gas dissolved in water will impact its vapor pressure. So a concentrated HCl solution will be more volatile than a dilute HCl solution.

In your original question, it seemed like you might be asking about periodic boiling point trends for the hydrogen halides, but it was unclear, and this lack of clarity is why you’ve gotten so many divergent responses.

In terms of boiling point trends: in general, boiling points get higher as you go down the periodic table, because heavier atoms are more polarizable (loosely speaking, their electrons respond more readily to an applied electric field), and the dispersion forces between molecules depend on this polarizability. This trend can also be seen for the chalcogen hydrides H2S, H2Se, H2Te, as well as the pnictogen hydrides PH3, AsH3, SbH3. You’ll notice, however, that the trend is broken for HF, H2O, and NH3. This is because F, O, and N participate in strong intermolecular interactions known as hydrogen bonding. These strong interactions raise the boiling points of these species considerably.

#### Lifeforbetter

1) “Someone” is not an acceptable source.
2) The list you give is the hydrogen halides arranged in order of increasing boiling point. All of the hydrogen halides are gases at room temperature. As has been mentioned previously, “volatility” is related to partial pressure. So a liquid at room temperature might still be considered volatile if it has a high vapor pressure.
3) Also mentioned previously, hydrogen halides refer to the free gases. Hydrohalic acid refers to that gas dissolved in water. The concentration of the gas dissolved in water will impact its vapor pressure. So a concentrated HCl solution will be more volatile than a dilute HCl solution.

In your original question, it seemed like you might be asking about periodic boiling point trends for the hydrogen halides, but it was unclear, and this lack of clarity is why you’ve gotten so many divergent responses.

In terms of boiling point trends: in general, boiling points get higher as you go down the periodic table, because heavier atoms are more polarizable (loosely speaking, their electrons respond more readily to an applied electric field), and the dispersion forces between molecules depend on this polarizability. This trend can also be seen for the chalcogen hydrides H2S, H2Se, H2Te, as well as the pnictogen hydrides PH3, AsH3, SbH3. You’ll notice, however, that the trend is broken for HF, H2O, and NH3. This is because F, O, and N participate in strong intermolecular interactions known as hydrogen bonding. These strong interactions raise the boiling points of these species considerably.
HCl HF
1) “Someone” is not an acceptable source.
2) The list you give is the hydrogen halides arranged in order of increasing boiling point. All of the hydrogen halides are gases at room temperature. As has been mentioned previously, “volatility” is related to partial pressure. So a liquid at room temperature might still be considered volatile if it has a high vapor pressure.
3) Also mentioned previously, hydrogen halides refer to the free gases. Hydrohalic acid refers to that gas dissolved in water. The concentration of the gas dissolved in water will impact its vapor pressure. So a concentrated HCl solution will be more volatile than a dilute HCl solution.

In your original question, it seemed like you might be asking about periodic boiling point trends for the hydrogen halides, but it was unclear, and this lack of clarity is why you’ve gotten so many divergent responses.

In terms of boiling point trends: in general, boiling points get higher as you go down the periodic table, because heavier atoms are more polarizable (loosely speaking, their electrons respond more readily to an applied electric field), and the dispersion forces between molecules depend on this polarizability. This trend can also be seen for the chalcogen hydrides H2S, H2Se, H2Te, as well as the pnictogen hydrides PH3, AsH3, SbH3. You’ll notice, however, that the trend is broken for HF, H2O, and NH3. This is because F, O, and N participate in strong intermolecular interactions known as hydrogen bonding. These strong interactions raise the boiling points of these species considerably.
If what i meant is acid
HCl HBr HI HF
Which most to least volatile?

"Is hydrohalic acid volatile?"

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