A white sodium salt dissolves in water to give a solution that is neutral to litmus. When silver nitrate solution is added to the solution, a white precipitate is obtained which does not dissolve m dilute ${\mathrm{HNO}}_3$ • The anion is:

${\mathrm{Cl}}^{-}$ ions react with ${\mathrm{AgNO}}_3$ ​to form a white curdy ppt of $\mathrm{AgCl}$, which is water insoluble and also insoluble in dil ${\mathrm{HNO}}_3$​ but soluble in dilute ammonia due to the formation of the soluble complex.
$\mathrm{NaCl}$ (neutral to litmus);

${\mathrm{Cl}}^{-}+{\mathrm{AgNO}}_3⟶\mathrm{AgCl}\downarrow$ (white ppt.)

$\mathrm{AgCl}+2{\mathrm{NH}}_3\to \left[\mathrm{Ag}{\left({\mathrm{NH}}_3\right)}_2\right]\mathrm{Cl}$