Question

Why do solutions of NaNO3 abd Mg(NO3)2 behave differently when aqueous ammonium is added?

A compound is known to be Na2CO3, Na2SO4, NaOH, NaCL, NaC2H3O2 or NaNO3-. When barium nitrate solution is added to a solution containing the unknown a white precipitation forms. No precipitate is onserved when a magnesium nitrate solution is added to a solution containing the unknown. What is the identity of the unknown compound? Explain reasoning

Answer 1

Why do solutions of NaNO3 abd Mg(NO3)2 behave differently when aqueous ammonium is added?

NaNO3 --> Na+ + NO3-

there is no interaction between NH3 and NH4+ ions

for:

Mg(NO3)2 ...

it is most likely that addition of NH3, in solution, will form plenty of OH- via

NH3 + H2O <--> NH4+ + OH-

so

Mg+2 + 2OH- <--> Mg(OH)2(s)

the solubility of Mg(OH)2 is limited, so you expect to see precipitate

A compound is known to be Na2CO3, Na2SO4, NaOH, NaCL, NaC2H3O2 or NaNO3-. When barium nitrate solution is added to a solution containing the unknown a white precipitation forms. No precipitate is onserved when a magnesium nitrate solution is added to a solution containing the unknown. What is the identity of the unknown compound? Explain reasoning

Ba(NO3)2 --> white precipitate

Mg(NO3)2 --> no precipitate

the compound is most likely BaCl2 which is NOT soluble, and it has white crystals