Question

A student was given a solid containing a mixture of nitrate salts. The sample completely dissolved in water, and upon addition of dilute HCl, no precipitate formed. The pH was lowered to about 1 and H2S was bubbled through the solution. No precipitate formed. The pH was adjusted to 8 and H2S was again bubbled in. This time, a precipitate formed. Which compounds might have been present in the unknown?

Answer 1

`Ni(NO_(3) )_(2)`

`Co(NO_(3))_(2)`

`Ca (NO_(3) ) _(2)`

Step-by-step explanation:

The will be a precipitation of the nitrates throughout the reactions.

The nitrates form after the pH was increased. One of the properties to this reaction is the slow solubility of the nitrate salts. The nitrates are strongly binding salts. Hence the slow formation of the salts.

Answer 2

• Ni(NO3)2
• Co(NO3)2
• Ca(NO3)2
• NaNO3

The last two require further qualitative analysis. So with only H2S tests the first two will appear.

Step-by-step explanation:

The other ions would have turned solid before the second addition of H2S.