The ion that can be precipitated by $HCl$ as well as $H_2S$ is

When $H_2S$ gas is passed through an $HCl$ solution containing $CuCl_2, HgCl_2, BiCl_3$,and $CoCl_2$,which of the following will not precipitate?

$A$ solution is prepared by mixing a concentrated solution of $Co(NO_3)_2$ with a concentrated solution of $NaNO_2$ in $50\%$ acetic acid. $A$ solution of a salt containing metal $M$ is added to the mixture, and a yellow precipitate is formed. Metal $M$ is:

Which of the following compounds can produce Rinmann's green with $Co(NO_3)_2$ solution?

Which ion is detected using Nessler's reagent?

The $V^{-}A$ group precipitate was dissolved in $HNO_3$ and treated with an excess of $NH_4OH$. It gives a white precipitate because of: