Question 2

[jsfkt78927]

passage clearly says that silver is resistant to attack by acids and oxygen.... this question is bull. if h2s is the correct answer then o2 may as well be too.

[jellywing_2058]

I do not see your point. H2S is not an acid.

Basically, as you mentioned the gas cannot be oxygen nor acid which eliminates answer choice A. Then by looking at the precipitates, we see a change in color of silver when it reacts with I or S containing compounds; only answer choice D (H2S) contains this atom.

[jsfkt78927]

Ha! "h2s is not an acid". Who are you kidding? Ill concede it may not be a strong acid, but it certainly is at least a weak acid. One could easily determine this from the question that follows, which gives its first and second Ka's. Further more, if silver is resistant to "acids" as stated in the passage, i would also assume that since H2S is a weak acid then silver is even more so resistant to attack by h2s. Bad question - no wonder it's "intense".

[hua8986059]

ya H2S but when dissolved in water it will become sulfuric acid right?

I just didn't know what tarnished silver looked like..

my mistake on this was not reading passage closely, I believe if I had, I would have picked H2S over O2 since it is stated in the passage not to pick O2.

I have trouble finishing one of the previous physicals section on time so I employed the not reading passage formula for Physicals. For the most part is works on GS tests, but failed me on this question.


this is from wikipedia

Hydrogen sulfide is slightly soluble in water and acts as a weak acid, giving the hydrosulfide ion HS− (pKa=6.9 in 0.01-0.1 mol/litre solutions at 18°C) and the sulfide ion S2− (pKa=11.96). A solution of hydrogen sulfide in water, known as sulfhydric acid or hydrosulfuric acid,[3] is initially clear but over time turns cloudy. This is due to the slow reaction of hydrogen sulfide with the oxygen dissolved in water, yielding elemental sulfur, which precipitates out.

[mohsinalam5969]

Tarnishing of silver happens because silver undergoes a chemical reaction with sulfur-containing substances in the air.The presence of Hydrogen Sulfide in any material that silver comes into contact with, is one of the prime reasons for silver tarnish. Sulfur containing materials generally cause silver to tarnish and Hydrogen Sulfide is just one of these. Materials like wool, rubber bands, fuels derived from fossils, a few types of paints and rubber (latex) gloves are some of the common materials that cause tarnishing of silver. Certain foods like eggs and onions also hasten the silver tarnish process. You can therefore realize that, touching silver jewelry with oily hands or after a meal could also stain your silver jewelry with tarnish. The extent and speed with which your silver jewelry tarnishes is also related to the climate and in general, high humidity would result in silver tarnishing much faster. So the answer option D is correct instead of Oxygen..thanks