If I dissolve 1 g of sodium bicarbonate powder ($\ce{NaHCO3}$) into 400 ml of distilled water, what will the pH of the resulting solution be?
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$\begingroup$ This appears to be a homework type question, please share your thoughts and attempts towards the solution. For formatting help visit the help center and for more information about this page, take the tour. $\endgroup$– Martin - マーチン ♦Commented Sep 11, 2014 at 3:34
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$\begingroup$ I'm an artist. I'm using baking soda in water to deacidify drawings on newsprint so they can be mounted and framed. (See my other question on the topic.) This is the recipe I'm using, and in case anyone asks me how strong my buffering solution is, I'd like to have more of an answer than "Well, it turns red cabbage juice blue." $\endgroup$– Laura WCommented Sep 11, 2014 at 3:42
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$\begingroup$ Well you're going about it the wrong way. You need to start with so called "acid free paper." en.wikipedia.org/wiki/Acid-free_paper The gist is that you can't get the lignin (which makes acid when it decomposes) out of the paper by neutralizing the current state of the paper. Thus making the paper less acidic now will slow the decay, but it won't stop it. The point is that if you really want your drawings to last, then start off with a better grade of paper. $\endgroup$– MaxWCommented Jan 31, 2017 at 22:46
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1 g of sodium bicarbonate in 400 mL of water will give an approximately 30 mM solution with a pH of ~8.4. The interesting thing about the pH of solutions of amphiprotic compounds is that so long as the concentration of the salt is significantly larger than its Ka and Kb, the solution pH only depends on the dissociation constants. Basically any amount of bicarbonate above 10 mM or so will have the same pH in solution, so pH is not a good indicator of how much acid you can neutralize with it.
I'm not really sure what good this information will do you. How much this solution will be able to affect the paper is going to depend on how much paper you use for a given volume of solution and how acidic the paper is. I don't know much about paper—it could be that it doesn't really matter if you go overboard on the bicarbonate. It might be as simple as making a concentrated solution, testing periodically that your bath hasn't become acidic, similar to photographic stop bath, which has a pH indicator that changes colour when the bath is not acidic anymore. If residual bicarbonate is a problem, rinsing with water afterwards is probably advisable.
answered Sep 11, 2014 at 5:22
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$\begingroup$ This answer did me a great deal of good because it led you to my first question, and your answer there is what led me to the really important information I was looking for. (Though I'll probably be following up with a question about the pH of calcium bicarbonate dissolved in seltzer water as soon as I get hold of some of that. Or maybe I'll just see if my local brewing store has litmus paper.) $\endgroup$– Laura WCommented Sep 11, 2014 at 16:28