Question

Which of the following doesn't produce a precipitate when dil.HCl is added?
1. $ NaAl{{O}_{2}} $
2. $ Na_{2}Zn{{O}_{2}} $
3. BiOCl
4. $ AgN{{O}_{3}} $
5. NaOCl

Answer 1

Hint: Hydrochloric acid, commonly known as muriatic acid, is a hydrogen chloride aqueous solution. It's a colourless liquid with a strong, unpleasant odour. It's considered a strong acid. In the digestive tracts of most animal species, including humans, it is a component of stomach acid. Hydrochloric acid is a common laboratory reagent and chemical used in industry.

Complete answer:
Precipitation in aqueous solution is the transformation of a dissolved material into an insoluble solid from a supersaturated solution. The precipitate is the solid that forms. The precipitant is the chemical reagent that causes the solid to develop in an inorganic chemical process that results in precipitation. The Supernate' or'supernatant' is the clear liquid that remains above the precipitated or centrifuged solid phase. When solid impurities separate from a solid phase (e.g., metallurgy and alloys), the concept of precipitation might be extended to other areas of chemistry (organic chemistry and biochemistry) and even applied to solid phases (e.g., metallurgy and alloys).
1
Sodium aluminate is what this is. Aluminum is an amphoteric metal. When the aluminate ion takes a proton, an acid-base reaction occurs, resulting in a precipitate of aluminium hydroxide:
 $ \mathrm{AlO}_{2(a q)}^{-}+H_{(a q)}^{+}+\mathrm{H}_{2} \mathrm{O}_{(l)} \rightarrow \mathrm{Al}(\mathrm{OH})_{3(s)} $
This might dissolve in $ \mathrm{XS} $ acid to produce $ A l_{(a q)}^{3+} $
This can be written as $ \mathrm{Al}(\mathrm{OH})_{4}^{-} $ or $ \left.\left[\mathrm{Al}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}(\mathrm{OH})_{4}\right)\right]^{-} $
This reaction is crucial in the purification of bauxite, an aluminium mineral, to produce alumina, which is aluminium oxide. $ \mathrm{Al}_{2} \mathrm{O}_{3} $ .
2 .
This is zincate of sodium. Zinc is also amphoteric, and a comparable reaction happens to produce zinc hydroxide precipitate:
 $ Z n O_{2(a q)}^{2-}+2 H_{(a q)}^{+} \rightarrow Z n(O H)_{2(s)} $
This might dissolve in $ XS $ acid to produce $ Z n_{(a q)}^{2+} $
the zincate ion can be written as $ \mathrm{Zn}(\mathrm{OH})_{4}^{2-} $
3 .
BiOCl is insoluble but you might get some hypochlorous acid:
 $ H_{(a q)}^{+}+O C l_{(s)}^{-} \rightleftharpoons H O C l_{(a q)} $
At low pH this might go on to produce chlorine gas:
 $ 2 \mathrm{HOCl}_{(a q)}+\mathrm{Cl}_{(a q)}^{-} \rightleftharpoons \mathrm{Cl}_{2(g)}+\mathrm{H}_{2} \mathrm{O}_{(l)} $
4 .
This produces a white precipitate of silver chloride:
 $ A g_{(a q)}^{+}+C l_{(a q)}^{-} \rightarrow A g C l_{(s)} $
 $ 5 . $
This forms hypochlorous acid:
 $ H_{(a q)}^{+}+O C l_{(a q)}^{-} \rightleftharpoons H O C l_{(a q)} $
At low pH this might go on to produce chlorine gas:
 $ 2 \mathrm{HOCl}_{(a q)}+\mathrm{Cl}_{(a q)}^{-} \rightleftharpoons \mathrm{Cl}_{2(g)}+\mathrm{H}_{2} \mathrm{O}_{(l)} $
No precipitate is formed.
Hence option 5 is correct.

Note:
The start of nucleation is a critical stage in the precipitation process. The development of a solid particle necessitates the establishment of a solution interface. The relative surface energy produced between the solid and the solution, as well as the dissolving reaction free energy (endothermic or exothermic activity followed by a rise in entropy), cause energy shifts. No precipitation happens if the energy changes aren't favourable, or if there aren't enough appropriate nucleation sites, and the solution remains supersaturated.