Science Buddies: "Ask an Expert"

My son is doing a science fair projecgt in which we are going to measure how fast a pain reliever dissolves in stomach acid. For this we bought muriatic acid with 31.45% hcl. If we should get a ph of 2, how many parts of muriatic acid to water should we mix? Thanks

Hello and Welcome to the Forum!

I'm not a chemist, so I'm hoping my response will encourage one to chime in!

Here are some references I found while researching this issue: http://en.wikipedia.org/wiki/Hydrochloric_acid has a nice table for pH vs. concentration. I looked up stomach acid pH, and found answers ranging from 1 to 3, so I would guess 2 is in the middle of those numbers. From the above chart, I would extrapolate that you want a concentration of around 0.1% - around 300 times less concentrated than the muriatic acid you have. I would recommend getting some pH paper or indicators to be sure that you've diluted it enough.

Please be careful diluting acid - you might search the web for safe methods to do this - here is one example: http://www.wikihow.com/Dilute-an-Acid

I hope this helps - let us know how your experiement progresses.

Keith

PS: Here's a nice chart: http://en.wikipedia.org/wiki/File:PH_scale.png