Sodium Bicarbonate and Citric Acid

[TylerH]

Homework Statement

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.

Homework 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.

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.

 

[chemisttree]

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

 

[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?

 

[chemisttree]

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

 

[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.

 

[Borek]

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^-?

 

[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?

 

[Borek]

Sodium carbonate comes to mind.

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

 

[TylerH]

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

 

[Borek]

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

 

[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.

 

[Borek]

what is there to consider?

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

 

[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.

 

[Borek]

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?

 

[TylerH]

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

 

[Borek]

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.

 

[TylerH]

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

 

[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?

 

[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.

 

[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.

 

[TylerH]

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?

I'm not trying to freebase it, it's just that without pH of 10 a significant amount of the target chemical will stay in the water instead of going to the xyxol.

 

[JohnRC]

I'm not trying to freebase it, it's just that without pH of 10 a significant amount of the target chemical will stay in the water instead of going to the xyxol.

Whatever is xyxol? The only web reference I can find to this mysterious substance is one that links to Mitt Romney's election campaign!

Is it a misprint for xylol/xylene? If so, you really should not be handling this irritant and carcinogenic solvent.

If, as you seem to be saying, you are not a trained chemist, it is the height of stupidity to be trying to do a chemical synthesis with a "target compound" in mind anyway.