Hi,
I’m using phosphoric acid (H3PO3) to clean cement off some brick pavers and I’d like to neutralize it with either bicarbonate of soda (NaHCO3) or quicklime (CaO) before washing it into the soil.
I read on the net that because phosphoric acid has 3 hydrogen molecules and bicarbonate of soda has 1, I therefore need to use three times as much bicarb to neutralize the acid.
Is this correct?
Either way, can anyone tell me how many grams of bicarb or lime I’ll need per mm of acid to neutralize it?
Thanks in advance.
Neutralizing Phosphoric Acid
Moderators: Xen, expert, ChenBeier
H3PO3 + 3NaHCO3 = Na3PO3 + 3H2CO3
per mm of acid? dont you mean ml? It depends how concentrated is that acid
so for example:
for 81.9 g of 100% H3PO3 (1 mol) you need 3 * 84 = 252 g of NaHCO3
so if you tell me how much of the acid and how concentrated it is, I (or someone else) can tell you how much of bicarb or quicklime you need
per mm of acid? dont you mean ml? It depends how concentrated is that acid
so for example:
for 81.9 g of 100% H3PO3 (1 mol) you need 3 * 84 = 252 g of NaHCO3
so if you tell me how much of the acid and how concentrated it is, I (or someone else) can tell you how much of bicarb or quicklime you need
-
- Jr. Member
- Posts: 8
- Joined: Mon Apr 02, 2012 7:04 am
Hi,
The product is called Phosphoric Acid Cleaner made by Spirit, and "contains 22% phosphoric acid solution". I'm using it undiluted.
As for how much acid, I can only estimate that the entire job will require 1 litre.
So, 1 litre of 22% acid.
Cheers
Oops, yes, I meant ml.KriggY wrote: per mm of acid? dont you mean ml?
The product is called Phosphoric Acid Cleaner made by Spirit, and "contains 22% phosphoric acid solution". I'm using it undiluted.
As for how much acid, I can only estimate that the entire job will require 1 litre.
So, 1 litre of 22% acid.
Cheers
-
- Jr. Member
- Posts: 8
- Joined: Mon Apr 02, 2012 7:04 am
Thanks KriggY,
Now I have no more excuses for not doing this job... darn!!
If you're interested, here's the link for my information on neutralizing phosphoric acid.
http://www.kchemistry.com/molarity.htm
Cheers
Now I have no more excuses for not doing this job... darn!!
If you're interested, here's the link for my information on neutralizing phosphoric acid.
http://www.kchemistry.com/molarity.htm
Cheers
-
- Jr. Member
- Posts: 8
- Joined: Mon Apr 02, 2012 7:04 am
Clarification re Phosphoric Acid
Hi,
Can somebody please clarify whether the formula for phosphoric acid is H3PO4 or H3PO3?
KriggY went to some trouble to assist me with calculating the amount of bicarb needed to neutralize phosphoric acid, but I've since found a discrepency with the formula I gave.
Also, I'm not sure where the 84.01g/mole comes from. I need to know this as I'm using an 85% solution now instead of 22% and will need to make an adjustment.
Thanks a million.
Can somebody please clarify whether the formula for phosphoric acid is H3PO4 or H3PO3?
KriggY went to some trouble to assist me with calculating the amount of bicarb needed to neutralize phosphoric acid, but I've since found a discrepency with the formula I gave.
Also, I'm not sure where the 84.01g/mole comes from. I need to know this as I'm using an 85% solution now instead of 22% and will need to make an adjustment.
Thanks a million.
-
- Distinguished Member
- Posts: 396
- Joined: Mon Mar 19, 2012 10:12 pm
Phosphoric or Phosphorous?
Sodium bicarbonate is NaHCO3, with a molar mass of 84.007 g/mol.
___________________________________________________________
Phosphoric acid is H3PO4, with a molar mass of 97.994 g/mol. 85% solution has a density of 1.685 g/mL.
H3PO4 + 3 NaHCO3 = Na3PO4 + 3 H2CO3
w[base]
= r[base:acid] * m[base] * c[acid] * d[acid] / m[acid]
= 3 * (84.007 g/mol) * 0.85 * (1.685 g/0.001L) / (97.994 g/mol)
= 3683.(5) g sodium bicarbonate per L of phosphoric acid.
___________________________________________________________
H3PO3 is Phosphorous acid with a molar mass of 82.00 g/mol. Make sure you know which one you have. Among other things, phosphorous acid is dibasic, not tribasic like phosphoric acid. (It will only donate two hydrogen atoms in an acid-base reaction; the third hydrogen is not acidic.)
Also, it's usually stocked as a powder, not a liquid.
H3PO3 + 2 NaHCO3 = Na2HPO3 + 2 H2CO3
w[base]
= r[base:acid] * m[base] * w[acid] / m[acid]
= 2 * (84.007 g/mol) * 1 g / (82.00 g/mol)
= 2.049 g sodium bicarbonate per 1 g of phosphorous acid.
___________________________________________________________
Phosphoric acid is H3PO4, with a molar mass of 97.994 g/mol. 85% solution has a density of 1.685 g/mL.
H3PO4 + 3 NaHCO3 = Na3PO4 + 3 H2CO3
w[base]
= r[base:acid] * m[base] * c[acid] * d[acid] / m[acid]
= 3 * (84.007 g/mol) * 0.85 * (1.685 g/0.001L) / (97.994 g/mol)
= 3683.(5) g sodium bicarbonate per L of phosphoric acid.
___________________________________________________________
H3PO3 is Phosphorous acid with a molar mass of 82.00 g/mol. Make sure you know which one you have. Among other things, phosphorous acid is dibasic, not tribasic like phosphoric acid. (It will only donate two hydrogen atoms in an acid-base reaction; the third hydrogen is not acidic.)
Also, it's usually stocked as a powder, not a liquid.
H3PO3 + 2 NaHCO3 = Na2HPO3 + 2 H2CO3
w[base]
= r[base:acid] * m[base] * w[acid] / m[acid]
= 2 * (84.007 g/mol) * 1 g / (82.00 g/mol)
= 2.049 g sodium bicarbonate per 1 g of phosphorous acid.
-
- Jr. Member
- Posts: 8
- Joined: Mon Apr 02, 2012 7:04 am