Answer to Question #70946 in General Chemistry for Jane

Question

You have an unknown substance that:

a) when heated with concentrated sulfuric acid, a colorless gas evolved

b) an aqueous solution of the salt produced a cloudy white precipitate when aqueous silver nitrate solution was added

c) is a white crystalline like solid readily dissolved in water

d) upon reaction w/ aqueous NaOH a gas evolved which turned moist red litmus paper blue

Suggest a possible identity for this salt- remember a salt contains both an anion and a cation. explain your reasoning

Answer 1

A possible answer – ammonium chloride (NH4Cl). Ammonium chloride is a white crystalline salt that is highly soluble in water.

It reacts with concentrated solution of sulfuric acid to produce ammonium sulfate and hydrogen chloride (if boiling colorless gas of HCl evolves):

2NH4Cl + H2SO4 → (NH4)2SO4 + 2HCl↑

When aqueous solution of NH4Cl is mixed with aqueous AgNO3 solution a cloudy white precipitate of AgCl produces:

NH4Cl + AgNO3 → NH4NO3 + AgCl↓

And, finally, upon reaction with aqueous NaOH a gaseous NH3 evolves which turnes moist red litmus paper blue:

NH4Cl + NaOH → NaCl + NH3↑+H2O