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H2O+HCL -> what gas?

  1. Jun 24, 2004 #1
    I work at a pool, and to keep the pH constant (chlorine is a base I suppose), there is a vat of water and hydrochloric acid which is pumped into the pool when the pH reaches a certain level of basicness. Anyway, it ran out today and it's the lifeguard's (my) responsibility to re-fill the tank with water and add hydrochloric acid to it. When I did this, I noticed that there was a steam coming from the vat. I was careful to hold my breath and not inhale any of it, and was curious what exactly it was, and if I should be supplied with some sort of gas-mask for this task.
  2. jcsd
  3. Jun 24, 2004 #2


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    I dont think it makes a gas

    H2O + HCl -> H+(aq) + Cl-(aq)

    the hydrochloric acid just breaks up into ions, perhaps the gas really was steam, or possible resulting from another reaction inside the container, if you put a metal into hydrochloric acid, then it makes hydrogen gas and a salt, for example:
    6HCl(aq) + 2Al(s) -> 3H2(g) + 2AlCl3(s)
    hydrochloric acid + aluminum makes hydrogen gas and aluminum chloride

    did you by chance happen to smell much of it?
  4. Jun 24, 2004 #3
    Didn't smell any of it, out of fear it was chlorine gas or anything else that might be dangerous. The vat is plastic, and there was actually a dead insect in there, so one of those could have cuase the reaction possibly?
  5. Jun 24, 2004 #4


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    I doubt that the insect caused it.

    even if you try not to smell something, like chlorine gas, it is still pretty hard not to smell it (it just sneaks it's way in), So I am thinking that if that is what it was, you would have smelled some of it.

    was the gas comming out since you had first oppened the container, or only after you added the HCl? Have you ever experienced this before?
    was the inside of the container hot, like an oven, could it just be evaporating some water?
  6. Jun 25, 2004 #5
    The container was near empty when I opened it. I filled it with mostly water, and then added the HCl, I felt no heat from the container, the gas was white and rose very slowly, very much like water vapor. Again, I did not inhale, and noticed no odor.
  7. Jun 25, 2004 #6
    HCl is a gas.

    The stuff you used was muriatic acid I reckon, and they dissolve the gas in water.

    What you saw was probably the HCl gas coming out from the solution. It fumes quite readily, especially after being contained inside a bottle for a set amount of time.
  8. Jun 25, 2004 #7


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    You need to have a very concentrated solution of HCl to see fumes. If the fumes were coming out of the HCl bottle, then thunderfvck is right. You are seeing HCl fumes. HCl is a slightly heavy gas (20% heavier than air), hence will not rise very fast. Also, it is a very corrosive acid and you don't want to be inhaling it. And be careful not to get it on your skin (wear gloves while handling). Check out the MSDS for HCl :

    http://www.chem.tamu.edu/class/majors/msdsfiles/msdshcl.htm [Broken]
    Last edited by a moderator: May 1, 2017
  9. Jun 25, 2004 #8


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    If had added the acid solution to the alkaline I suppose reactions can occur which produce gases. For the most part, the gas was probably not HCl, anyone who has taken a lab course knows that HCl is a fuming liquid at room temperature and has a pungent odor, in contrast with what you said to be an odorless gas. It could have also reacted with impurities, this would expain the transient nature of the reaction you observed.

    Online help with chemistry
    http://groups.msn.com/GeneralChemistryHomework [Broken]
    Last edited by a moderator: May 1, 2017
  10. Jun 27, 2004 #9
    It's also an exothermic reaction when you dilute HCl in water. My guess is it is some mixture of HCl (g) and water vapor.
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