How much baking soda for acid neutralizing?

[68Malibu383]

I have 1,200 of garage floor that I plan to acid wash with hydrochloric acid (4 parts water, 1 part acid). I plan to use 5 gallons of acid total.

I found instructions that state to mix one pound of baking soda per gallon of water and sprinkle over the acid when its time to rinse. But, anyone have an idea how many gallons of this solution would be needed to neutralize the amount of acid I plan to use?

 

[Mr. D]

I don't know the answer to your question but funny you ask. I have been thinking the same thing for my upcoming project.

If we acid etch our garage floor than just rinse it out to the driveway won't the acid etch start etching the driveway??????

 

[Shiftless]

In order to get a knowledgeable reply to your question, you will have to state the concentration of your hydrochloride acid.
It’s gonna be well beyond a couple of orange boxes from the grocery store.
In case you didn’t already know, when diluting acid, always pour acid into the water. NEVER water into the acid. Under some circumstances that can explode and send acid into your face.

BE CAREFUL!

 

[Gerald O]

When it no longer fizzes then you know the acid has been neutralized.

 

[JimNC]

Assume that you’re starting with 5 gal of 37% HCl.

Since HCl will contribute 1 H and your baking soda (NaOH) will contribute 1 OH to neutralize I’d either figure out the moles so you know, or assume that you’ll need about 20lbs of baking soda to neutralize about 16lbs of 100% HCl.

The fumes from HCl are highly corrosive, you’ll want good ventilation.

 

[68Malibu383]

Thanks for the information and tips. I don't recall enough of chemistry to solve this one. Guess I'll buy a bunch and if I have too much, I'll have a lifetime supply for the fridge.

The reason I wanted to neutralize, or come close, is so that I don't harm my driveway when I rinse this stuff out of the garage.

I do have a full-face 3M respirator with acid gas cartridges, so I should be ok - thanks.

 

[LegacyIndustrial]

I use 1/2 cup per gal.


Sent from my iPhone using The Garage Journal mobile app

 

[flyingblind]

Ph 7 is neutral. You can get ph strips at any pool supply

 

[4xdog]

Assume that you’re starting with 5 gal of 37% HCl.

Since HCl will contribute 1 H and your baking soda (NaOH) will contribute 1 OH to neutralize I’d either figure out the moles so you know, or assume that you’ll need about 20lbs of baking soda to neutralize about 16lbs of 100% HCl.

The fumes from HCl are highly corrosive, you’ll want good ventilation.

Baking soda is sodium bicarbonate (NaHCO3), not caustic soda (NaOH).

The neutralization reaction is:
NaHCO3 + HCl → NaCl + H2O + CO2 (as fizzy gas)

You can see it's 1:1 molecule-to-molecule. But as the molecules don't weigh the same, one needs to ratio the weights to get the molecular ratio right.

Baking soda has a molecular mass of 84 g/mole. HCl has a molecular mass of 36.5. So in general, use twice the amount of baking soda as hydrochloric acid to get the molecules at about 1:1.

As noted earlier, the concentration in your aqueous HCl is probably thirty-some percent. Correct for that when you use baking soda -- it only needs to neutralize the HCl part, not the water part, in your acid.

 

[JimNC]

Baking soda is sodium bicarbonate (NaHCO3), not caustic soda (NaOH).

The neutralization reaction is:
NaHCO3 + HCl → NaCl + H2O + CO2 (as fizzy gas)

You can see it's 1:1 molecule-to-molecule. But as the molecules don't weigh the same, one needs to ratio the weights to get the molecular ratio right.

Baking soda has a molecular mass of 84 g/mole. HCl has a molecular mass of 36.5. So in general, use twice the amount of baking soda as hydrochloric acid to get the molecules at about 1:1.

As noted earlier, the concentration in your aqueous HCl is probably thirty-some percent. Correct for that when you use baking soda -- it only needs to neutralize the HCl part, not the water part, in your acid.

I’m a little embarrassed about forgetting that baking soda is sodium bicarbonate.

 

[4xdog]

Hah! But your stoichiometry was right on, and NaOH makes a "cleaner" neutralization reaction, yielding only a salt and water.

 

[James-W]

OR, you could grind the floor and not worry about all this.

 

[4xdog]

When it no longer fizzes then you know the acid has been neutralized.

In practice, this is good advice and exactly what I’d do.

Use my calculations earlier to estimate how much baking soda you’re likely to need. Use Gerald O’s advice as a guide to knowing when you’re done. As baking soda is a weak-ish alkali it won’t hurt if you overneutralize a bit.

 

[southalabama]

Now I'm regretting sleeping through chemistry.

 

[Dagny]

Won't some of the acid be neutralized by the reaction with the concrete?

 

[JimNC]

Won't some of the acid be neutralized by the reaction with the concrete?

Yes (hey, forum requires 4 characters for a post)

 

[68Malibu383]

Here is what I did... found sodium bicarbonate at Walmart in 12 lb bags for $8/bag. I used just under three bags to neutralize 13 gallons of HCL mixed with water at ~3.5:1 ratio with 31% HCL. This did not cause discoloration to my driveway when I rinsed it out. I bought pool PH strips but they only go down to 6, so that was worthless. Thanks for the replies!

 

[Garage Flooring]

Have a look at this article https://allgaragefloors.com/acid-etch-garage-floor/