GS-2 Physical Sciences Question 13

[chewei684569]

Why does HCl, a liquid, have partial pressure?

[mcat_premed3832]

Whether a chemical is a solid, liquid or gas depends on pressure and temperature. In this particular case, we are told about a reaction which is "explosive" which suggests an extremely high temperature which is consistent with the gaseous form of HCl.

Even at room temperature, however, HCl (like any liquid including water) would have a certain vapor pressure. In other words, there would be a certain percentage of gaseous HCl even at room temp (meaning a partial pressure of HCl in the air above the liquid at equilibrium/closed container).

But all of the above is just background information since the data was provided.

[mohsinalam5969]

The liquid hydrochloric acid is actually a solution of hydrogen chloride gas in water.
The HCl solution emits HCl vapors into the space above the liquid surface. The tendency of the HCl to escape is measured as a vapor pressure - the higher this pressure, the more HCl escapes.
so due to the presence of few gas in the solution it has a vapour pressure to some extent..
it can b more clearly understood as follows

30% - 40% hydrochloric acid (HCL)is a volatile liquid, it's boiling point is 53C (127F), for that reason it form fumes at the normal room temperature.

10% HCL, is less volatile and emmits vapors same as water, it's boiling point is 100C (ca. 212F) .

Therefore any acid concentration above 10-20% will start fuming at abient temperatures.