Based on our last post outlining the differences between pH and acidity as measures of acid strength, a short exercise will help emphasize the differences. Here we will compare two deceptively similar acids: 5% store bought white vinegar and Coca-Cola classic.
White Vinegar
As stated before, 5% white vinegar has an acidity of 5% which means 5 grams of acetic acid (CH3COOH)
per 100 mL of vinegar. In addition, the pH usually is in the 2.5 – 2.7 range.
Coca-Cola Classic
Now, is Coca-Cola Classic as acidic as white vinegar? A first (but incorrect) assessment would look at the fact that the average pH of Coca-Cola Classic is about 2.53. This puts it at the lower range of white vinegar. However, as discussed before, the grams of acid per liquid is what matters since the quantity of acid dictates how much it can act (and dissolve) other compounds.
The active acid in Coca-Cola Classic is phosphoric acid (H3PO4). The average amount per can of coke works out to 17mg per 100 mL of Coca-Cola. This gives an acidity of only 0.017%. Granted, since phosphoric acid has three hydrogens instead of one like acetic acid there are some chemical considerations but they are not as relevant at this low concentration.
12 Comments on “pH and acidity exercise: Vinegar vs. Coca Cola”
Hi
Where did you get that value of 17mg/100ml of coke? Do you have a reference for this?
Cheers
The ultimate source for that number seems to be:
Scherz H, Senser F. Food composition and nutrition tables. Medpharm GmbH Scientific Publishers; Zurich: 1994
But I don’t have access to that book and got the number from this paper.
Aghili, H. A., Hoseini, S. M., & Yassaei, S. (2014). Effects of carbonated soft drink consumption on orthodontic tooth movements in rats. Journal of dentistry (Tehran, Iran), 11(2), 123.
If you have another, better number, let me know. Also I feel this probably varies by country and production location.
Can i get the procedure/method to determine the amount of acid in a carbonated drink.
And also the effect of temperature on the acid content.
You should use regular acid-base titration, probably with Sodium Hydroxide and a pH indicator like phenolphthalein. The temperature affects the acid content through changing the Ka that will cause more or less ion dissociation into the acid. You can calculate this effect by measuring the pH at different temperatures and estimating how Ka changes.
good
If coke is over 100 years old.. and people all over the world have comsumed it this long without any major problems ( outside of abuse overuse) . it can’t be that bad for the average person… ?
Hi, I never implied Coke was bad. I am not a nutritionist but acid wise, Coke is nowhere near as strong as vinegar. Let me know if this helps.
Very interesting and makes sense. So best stick with vinegar for cleaning limescale off taps. Coke would not be as effective.
Thanks a lot.
So what does this make the pH of Coca Cola?
As the article states, the pH of Coca Cola is around 2.53 but the concentration of phosphoric acid (acidity) is much lower than the acetic acid concentration in vinegar.
It would seem phosphoric acid content in Coca-cola is around 450 mg/l (so 45 mg per 100 ml). This is based on a school project I did and additionally this source which I referenced in my report. The pH I measured was same to the one presented here, however, the document I have linked says it should be a little lower. The value I got (441 mg/l) was achieved using potentiometric titration. I can’t be bothered to think why the phosphate content would be lower than acid content considering the 3 hydrogens do not weigh much.
https://www.ld-didactic.de/documents/en-US/EXP/C/C3/C3642_e.pdf
I believe coke is bad for you especially if consumed regularly…2.3oz of sugar per 350mls doesn’t sound healthy to me, not only does it rot your teeth but it can also contribute towards stomach ulcers not to mention that cancer feeds off sugar so in my opinion not only is coke an unhealthy acidic solution it’s so laden with sugar that with regular consumption it’s a formula for disease.