Hydrochloric Acid on Concrete

[billbeee]

Hi all,
A simple one for you guys who can remember your chemistry.
What is the gas or what do the fumes contain when in the process of acid etching concrete with hydrochlric acid (muriatic acid)?
Cheers
Bill

[silentC]

Hydrogen chloride?

[Alastair]

Gas produced would probably be hydrogen, but fumes would certainly include HCl, and chlorine.

[Skew ChiDAMN!!]

Going by my vague memories of high-school chem, I agree with Alistair: I'm pretty sure that it's only Hydrogen gas generated by the HCl reacting with the hydrated lime and any AlOxides.

There'd also be HCl fumes, but that's not from any reaction - you'd have the same amount of fumes if you poured HCl over a completely inert surface. It's never a good idea to sniff acid.

Chlorine could be generated from reactions with impurities in the conc, but would be so small as not to be a concern... I'd be more worried about a whiff of HCl fumes.

[Bleedin Thumb]

I think it goes like this

3 HCL + Ca(OH2) = H2 + CaCL2 + CL + H20
So by my reconing its hydrogen and Chlorine gas given off. It been a long time though so I may be way off.

EDIT just realised my Hydrogen doesn't add up. By changing the CL to HCL the equation does balance so I take it back about Chlorine gas.

Actually I'm not sure that Hydrochloric acid is what it is called.... maybe it actually should be called Hypochloric acid as I think HCL should be a gas?????? geeze it has been a long time...

[Skew ChiDAMN!!]

Hydrochloric Acid is right - Hypochloric Acid is HClO

...and Chlorine gas is diatomic (Cl2)

I used to love chem, but hated the damned equations... gimme a handful of nitropills and a bucket of dieseline any time!

[Bleedin Thumb]

But Skew isn't HCL a gas and when you combine it with water it disassociates to form HClO?


Edit No dont answer that I'm wrong but is my equation correct

3HCL + Ca(OH)2 = H2 + CaCL2 + HCL + H2O


PS how do you do those small 2's

[Skew ChiDAMN!!]

Pure HCL is a gas... but Hydrochloric acid is a solution of the gas suspended in good ol' water.

Edit No dont answer that I'm wrong but is my equation correct

3HCL + Ca(OH)2 = H2 + CaCL2 + HCL + H2O

My high school teacher wouldn't pass it. (Although to all practical intents and purposes ya got it right.) For starters, you have HCl on both sides, obviously one of the HCl's on the left isn't doing anything in the equation... so you can simplify it to

2HCl + Ca(OH)2 = H2 + CaCl2 + H2O

That looks right to me and it balances out but, like you, it has been a long time since I've broken out a chemistry book.

PS how do you do those small 2's

I cheated and just used the font size button at the top of the editor to use a size 1 font.

[mic-d]

Nope, you're all wrong!
I'll give you a hint - it's a greenhouse gas!

Cheers
Michael

[Skew ChiDAMN!!]

Ain't CO2 or Methane (CH4) as there's no carbon in HCl or concrete.

Hmmm... water vapour can be considered a greenhouse gas, but we already covered that. What else is there? Nitrous Oxide (NO2) and Ozone (O3)? Don't seem right. And I'm sure that chlorofluorocarbons, hydrofluorocarbons and perfluorocarbons aren't in the running.

Now you have me wondering. What do we win if we guess right?

[mic-d]

Ain't CO2 or Methane (CH4) as there's no carbon in HCl or concrete.

Hmmm... water vapour can be considered a greenhouse gas, but we already covered that. What else is there? Nitrous Oxide (NO2) and Ozone (O3)? Don't seem right.

Now you have me wondering. What do we win if we guess right?

Lots of carbon in concrete.
(if it's the mafia type )

try again
CHeers
Michael

[Skew ChiDAMN!!]

Lots of carbon in concrete.

Huh?

AFAIK, sand's primarily a silica, cement is a mixture of aluminium, calcium, iron and silica, then there's the gravel (usually a basalt), water and colouring - which are usually, I think, Al- or FeOxides.

I'm pretty sure modern conc doesn't include ash any more? Maybe in the hardeners in use now? But I thought they was CaCL based. Hmmm...

Mind you, I'm just making educated guesses here. I give up. My brain hurts.

[Bleedin Thumb]

Lots of carbon...as in CaCo3 + HCL = CaCl + H2Co3????


Mate its Friday arvo give us a break!

[Skew ChiDAMN!!]

D'OH! And I mentioned basalt...

try: CaCO3 + HCl = CaCl + H2O + CO2

... no... hang on... that doesn't balance. But along those lines...

[Bleedin Thumb]

No way that is too simple must be wrong