For water under standard conditions, the pK value is 14, which defines the pH range. The ranges can differ in matrices with different properties.

Sir Paul Milham somewhere I have read that acid mines have the negative pH value so that's why I want to clear it out. Well thanks for the contribution.

Always, in aqueous solutions, the pH values are positive (between 0 and 14). In concentrated solutions of strong mineral acids (or mixtures of acids), the pH-meters may indicate negative values, but these are rather due to the limitation of the electrode used to measure the pH.

Thank you Laura Bulgariu ma'am for the contribution. The concept you have discussed is absolutely right and authentic, but somewhere I have read that acid mines have negative value.

The KCl pH values are generally lower than water pH values but often it found to be close to or greater than pH values in water for the lower horizons of some highly weathered acidic soils (Ultisols), which indicates the presence of gibbsite and/or amorphous materials. A negative/zero/positive delta pH value indicates the presence of variable charge minerals such as gibbsites and/or sesquioxides.

Thank you Dilip Kumar Pal sir for such a nice explanation.

Ali A. Al-Homaidan thanks for the contribution

Dear Neeraj Pandey ,

Indeed, we all learn early on at high school level chemistry that the pH value ranges from 0-14. The reason is most likely because it is a convenient range that places the value for neutrality of pure water at 25 °C in the middle. However:

Purely mathematically it is clear that the pH could be lower than zero, since 10-2 mol/L renders pH 2 (because obviously -log 10-2= 2), 10-1mol/L renders pH 1, 100 renders pH 0 and logically upon further increasing the H3O+ concentration to 10+1 mol/L renders pH -1.

See for more about this matter this excellent and interesting paper:

Lim, K. F. (2006). Negative pH does exist. Journal of chemical education, 83(10), 1465 (see enclosed file)

here you can find and I quote "For example, commercially available concentrated HCl solution (37% by mass) has pH ≈ -1.1, while saturated NaOH solution has pH ≈15.0 (22). Hot springs near Ebeko volcano, with naturally occurring HCl and H2SO4, have estimated pH values as low as –1.7 (23, 24). Waters from the Richmond Mine at Iron Mountain, CA, have pH = -3.6 (25, 26).".

and see:

Nordstrom, D. K., Alpers, C. N., Ptacek, C. J., & Blowes, D. W. (2000). Negative pH and extremely acidic mine waters from Iron Mountain, California. Environmental Science & Technology, 34(2), 254-258 (see enclosed file).

Hope this answers your question.

Best regards.

if concentration of H+ is over 1M, pH should be negative? pH=- log[H+]

I never knew that pH could be a negative value.

I remember that when I was a nurse practitioner for bladder and bowel health finding that people who had long term Foley urinary catheters developed a high urinary pH due to the enzyme urease hydrolysing the urea as a result of bacterial action. Ammonia is produced and the urine then becomes very alkaline. Phosphates of calcium and magnesium are deposited and the catheter blocks due to encrustation.

In: https://www.researchgate.net/publication/271444659_Citrated_drinks_a_new_approach_to_encrustation

we suggested reducing the high pH by suggesting citrated drinks. It worked regarding the blocking of catheters, but I used to discuss the negative aspect dentally regarding the oral intake of - for example - the addition of lemon juice to drinking water, as carried out (and described in the article) by a patient of my co-author.

Dear Dr Neeraj Pandey . Any acid that yields a concentration of hydrogen ions with a molarity greater than 1 will be calculated to havea negative pH. For example, the pH of 12M HCl (hydrochloric acid) is calculated to be -log(12) = -1.08. But, you can't measure it with an instrument or test.

Thank you so much sir @Aref Waswaz

Kindly visit..

ed083p

1465.pdf

Whereas , The pH values for solutions are always between 0 and 14.

Thank you Ca Dr. Gaurav Bhambri Mary C R Wilson Guobing Xiang Aref Wazwaz

Ca Dr. Gaurav Bhambri hit the spot.

Never heard of negative pH, also because the value fluctuates between 0 and 14.

Where does this question come from ?

You are most welcome dear

Dr Neeraj Pandey

Wish you the best always.

Sir doubt should be cleared if it arises in mind and somewhere I have heard/ read that the pH of acid mines is towards the negative , which means negative pH

@Gioaachino de Candia

@Afreen Bano even I want to know the same

Dear Neeraj Pandey ,

I urge you and those interested to check previous replies more carefully (and pay special attention to the papers I suggested in my reply of December 25th, 2021). Too many wrong answers and assumptions are given. For example: Aref Wazwaz you state “But, you can't measure it with an instrument or test.” As indicated in my previous reply 6 days ago: there is! Read the indicated paper (enclosed file named as "full text") Nordstrom, D. K., Alpers, C. N., Ptacek, C. J., & Blowes, D. W. (2000). Negative pH and extremely acidic mine waters from Iron Mountain, California. Environmental Science & Technology, 34(2), 254-258 They extensively described how.

Ca Dr. Gaurav Bhambri nice that you suggest a pdf file, but this is the pdf file I already suggested... Furthermore, your statement “The pH values for solutions are always between 0 and 14” is not true. Again, read my previous reply and the two excellent papers I indicated:

Lim, K. F. (2006). Negative pH does exist. Journal of chemical education, 83(10), 1465 (see enclosed file)

Nordstrom, D. K., Alpers, C. N., Ptacek, C. J., & Blowes, D. W. (2000). Negative pH and extremely acidic mine waters from Iron Mountain, California. Environmental Science & Technology, 34(2), 254-258

Afreen Banu see my comment above and read the indicated paper (and references)

Best regards.

PS. My apologies for my somewhat grumpy tone but it is a little bit frustrating to see that an already answered question evolves into one with even more than less misconceptions. Wish everyone all the best in the new year anyway 😉

@Rob Keller sir I'm totally agreeing with your explanation and the paper you have shared..

As your Information, pH range is from 1 to 14. So, in fact, you can't measure negative pH value, meanwhile you can calculate negative pH values. For example 12 M of HCl is -1.8

Thank u so much @Mustafa sir

Negative pH is only theoretically possible not practical.