I'm doing an experiment and I'm supposed to have neutral basic and acid samples of solution.

Question

I just wanted to make sure that I knew which was which. (If I'm incorrect, please correct me)

Acid: 0.7ml 10% H2SO4 + 0.7ml 10% Na2WO4(sodium tungstate)

Basic: 0.7ml NaOH + saturated HgCl2

Neutral: 0.7ml saturated K2CO3

Thank you.

Responses

science(chem) - DrBob222, Saturday, September 20, 2008 at 10:42am 
I would expect the first one to be acid, the second to be basic and the third to be basic. K2CO3 is the salt of a strong base (KOH) and a weak acid (H2CO3) so it will hydrolyze to produce OH^- and that should make it basic. NaCl or KCl solutions will be neutral.

The last one was what was confusing me. The manual I'm using says that one should be acidic, basic, and neutral.

I don't know how this would work.
I was told in the manual that I would have one of each.

I do add ethanol to each as well (later) Would this affect the basisity/acidity thus making the last, neutral?

Thank you,
Dr.Bob

DrBob222 · Answer

K2CO3 is practically insoluble in alcohol. I looked in The Merck Index and it shows K2CO3 solution to be strongly alkaline (as the book puts it) with a pH about 11.6. I think the H2SO4/Na2WO4 might be somewhat of a buffer since H2SO4 has a k2 and tungstate ion will hydrolyze BUT with k1 being completely ionized I would not expect it to be neutral (perhaps just not as acid as one might expect with straight H2SO4). If I knew one of the three had to be neutral, I would pick on the second one in your list. My experience with NaOH and Hg^+2 is the formation of a ppt and if the Hg ppts that would leave a solid, practically insoluble, with NaCl. I think that comes the closest to being neutral of the three. I initially didn't pick this one because you didn't say anything about a ppt and I thought I just didn't remember. You know how we get with old age. But I looked it up tonight and I'm correct about the ppt.

~christina~ · Answer

Okay, thanks Dr.Bob.