# Sodium Bicarbonate and Citric Acid

1. Sep 17, 2012

### TylerH

1. The problem statement, all variables and given/known data

What salt is produced from sodium bicarbonate and citric acid? Just to be clear, this isn't actually homework. I would hope no professor would ever be so hard. I'm not even in chemistry. Although I did take it last year in high school.

2. Relevant equations

I really can't tell how either of these would break down into a net ionic equation, which, IIRC, is the first step to predicting salts.

From Wikipedia, I can tell that sodium bicarbonate will dissociate into a positive Na and the bicarbonate will have a negative O. But, I don't know how the citric acid will dissociate. I know it's acidic, because it has a bunch of carboxyls, but I don't know how they dissociate.

3. The attempt at a solution

Well, if I could break it down, I would look for positive ions that could match to negative ions, but intuition tells me that there are many different ions and I don't know how to match them in that case (for example, would. Also, I would also guess that there are some polyatomic ions, which I haven't learned anything about.

2. Sep 17, 2012

### chemisttree

The carboxyls on the citric acid dissociate by separating the carboxylate anion from the hydronium cation. Citric acid becomes citrate anion.

3. Sep 18, 2012

### TylerH

Okay, so, letting Ci be citrate, that would be
$$Ci^{-3} + 3H^{+1} + Na^{+1} + CO_2 + OH^{-1}$$.
Heuristically, I think Na would combine with Ci and the Hs and OHs would make water and the CO2 would be released as a gas. Am I correct that it would produce water, CO2, and sodium citrate?

4. Sep 20, 2012

### chemisttree

Your thinking is correct but you need to work on your neutralization equation. Should be a walk in the park for you.

5. Sep 20, 2012

### TylerH

I don't really know what you mean. Did I not separate some ions or something? As long as the products are correct, that's really all I'm concerned with.

6. Sep 20, 2012

### Staff: Mentor

Where did you got OH- from?

Can you ignore citrate and sodium for a moment and write net ionic reaction between H+ from strong acid and bicarbonate anion HCO3-?

7. Sep 20, 2012

### TylerH

Oh, that would be carbonic acid. Unfortunately, I just realized that baking soda doesn't have a high enough pH for the acid base extraction in mind. Are there any other bases can have a pH of at least 10 and a food safe salt with citric acid?

8. Sep 20, 2012

### Staff: Mentor

Sodium carbonate comes to mind.

Does "food safe" mean you are planning to eat whatever you prepare?

9. Sep 20, 2012

### TylerH

Yeah, probably. I got pH paper to make sure I'm not going to dissolve my insides.

10. Sep 20, 2012

### Staff: Mentor

pH paper is definitely not enough to be on the safe side, especially when you are not sure what you are doing.

11. Sep 20, 2012

### TylerH

Other than pH and possibly poisonous salts, what is there to consider? I didn't come up with the whole extraction myself; just the idea of substituting lemon juice and something else for HCl and NaOH. The desired pH's are 4 and 10.

12. Sep 20, 2012

### Staff: Mentor

Contamination. Baking soda is checked that it is food safe. When you use reagents from other sources, you can't be sure.

13. Sep 20, 2012

### TylerH

Since CO2 is available in a food grade quality for soda spritzers, how could I get the CO2 to dissolve into the water to make carbonic acid? If not that, sodium carbonate is available as pretzel salt, which I would hope is food safe.

14. Sep 20, 2012

### Staff: Mentor

Can't help you - that is, I can give you completely useless answer about what to do if you live in my neck of woods.

And what is pretzel salt?

15. Sep 20, 2012

### TylerH

It's salt for pretzels. Pretzels are a bread treat, see Wikipedia.

16. Sep 20, 2012

### Staff: Mentor

I know what pretzels are, I am asking what the pretzel salt is chemically. Quick googling which I did before asking didn't yield unambiguous answer.

17. Sep 20, 2012

### TylerH

Oh, it's just a general strong base. NaOH can be used, but sodium carbonate is also sometimes used as a substitute.

18. Sep 21, 2012

### chemisttree

It isn't the salt that is sprinkled on the pretzel. What you are describing is something that the unbaked pretzel is immersed in just before baking to get that dark coating. Good luck finding food grade sodium carbonate. I would use bicarbonate instead and adjust the stoichiometry to account for the partly neutralized carbonate.

What are you extracting that requires such a strong base? Are you free-basing something?

19. Sep 27, 2012

### JohnRC

In fact sodium carbonate is an unlikely food salt -- far too alkaline. Sodium bicarbonate (baking soda) and sodium acetate ("salt and vinegar" chips) are commonly used as food salts, but not sodium carbonate.

20. Sep 27, 2012

### JohnRC

Baking soda is food grade sodium bicarbonate. Food grade citric acid is readily available. Anything that you can produce by simply mixing these two with water and nothing else will not be poisonous. Nor will it necessarily be particularly pleasant!

Half a century ago, in rural Oz, we used to have a drink called "fruit saline". It would come as a white powder in a screw top tin with a plastic seal on the lid, intended to keep the contents very dry. Said contents were a powder, either white or a pale pastel colour, consisting of a mixture of citric acid, baking soda, and some fruit flavourings. You would take a heaped teaspoon of this stuff and stir it vigorously into about 200 mL of chilled water. After about 3 seconds it would start to fizz quite vigorously, and you would take out the spoon and quickly drink it while it was still fizzing. It was rather salty, but very refreshing on a hot day.

I have not seen this product for about 20 years (not really been looking for it either).
If you are trying to make something like this, it is important to calculate your relative quantities of citric acid so that only one of its three acidic protons is neutralized by bicarbonate. If you use larger quantities of bicarbonate your product will become steadily less acidic and saltier, greatly detracting from its taste.