H2S and pH Values

You wrote: "Take a certain quantity of plain water (i.e., pH = 7) and dissolve a corresponding amount of H2S (Hydrogen Sulfide, Hydrogen Sulphide) in the water."

It is not clear to me what you mean by "corresponding amount"--first of all, do you mean an equal amount of water and hydrogen sulfide? And, second, how are you measuring them (to determine equal amounts)--by weight, by volume (and, if by volume, you need to know the temperature and pressure of the H2S), or by counting molecules? ;-)

To your second question, yes, adding H2S will create an acid solution and will change the pH.

Hmm, why do I feel I've just been "homework phished"? Should I actually post this answer--well, I guess I'll consider this the "fool me once".

If it is homework, the OP did a poor job of translation.

I agree, the question is indecipherable.

I don't think you've given anything away.

Cheers.

I wouldn't advise to play with H2S and certainly with "corresponding amounts". It doesn't take many ppm's to kill you. (poisonous by inhalation)

The TLV for H2S is 10 ppm's. This gas will rapidly deaden your sense of smell once the concentration reaches 100 ppm's or so. Prolonged exposure in the 200 ppm range can prove FATAL for some individuals. Ed from NJ

What are you driving at?

Better don't play with hazardous chemicals

hopefully this is a theory question and you do not intend to actually try it!

I would suggest that you first read up on the safety aspects of H2S and even after reading about the dangers, I suggest that you DO NOT EVEN THINK ABOUT IT.

I work in the oil industry and I have manatory H2S training EVERY year. The dangers of H2S far outway the results from this experiment. you are playing with dangerous stuff, not only will it kill you, but others around you.

Well now while H2S is a danger, it is not necessarily all that bad. the training has more to do with the working conditions/environment and the broad range of qualifications that may be encountered amongst personnel involved. Some make have a little chemistry and toxicology background and many others might be borderline high school graduates with little or no science education. You could easily find more dangerous compounds in household products if mixed improperly, in a seemingly innocent and plausible action. Example pouring commercial drain cleaner into a clogged sink which has certain residential drain cleaners, which contain bleach, could easily kill a whole room full of people and/or cause chronic serious respiratory damage with much less volume. It really doesn't take much Chlorine gas to kill a room full of people, and even if you survive you are permenantly injured. A matter of one breath at 25 to 50 ppm can cause a relatively slow and very painful death as you develop pulmonary edema, the lungs fail and you suffocate in your own fluids, compounded by the irritation to the eyes mouth nose and in severe cases skin. Far nastier stuff is out there and common household materials I could buy at Home Depot, Walmart or Safeway.

Thank you very much indeed (for sharing your experience).

Most Commendable Effort.

Thank you again. Regards.

How are you going to get a corresponding amount of H₂S dissolved in Water. H₂S is not that soluble. At STP you will only get about 0.2M or 3800 ppm by mass to dissolve. I guess you could mean by volume, which would give you something less that about a quarter of the solubility limit for H₂S. So which method are you considering for a corresponding amount? From that dissolved portion the ionization constant is , pKa =6.89 for HS^- and pKa=11.96 for S^2-. At this point just solve like you would for the carbonate series using the different pKa's and Solubility, which are much less than carbon dioxide. Its a very weak acid forming agent about 3 orders of magnitude weak than CO₂.

Answer to question #1: Ph will be lower

Answer to question #2: Yes,the Ph will change

HiTekRedNek

Thank you for sharing your experience.

You are Noble indeed.

Regards.