Why does ammonium chloride form white crystals? [closed]








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Why does ammonium chloride ($\ce{NH4Cl}$) form white crystals on top of a test tube when heated?




I suppose you are not asking why crystalline $\ce{NH4Cl}$ is white.


Ammonium chloride decomposes upon heat
$$\ce{NH4Cl(s) ->[\Delta] NH3(g) + HCl(g)}$$


The top of the test tube is cold, and they recombine to generate the original salt.
$$\ce{NH3(g) + HCl(g) -> NH4Cl(s)}$$


This is the white crystal you see.


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