Which of the following ions forms a white precipitate upon the addition of $HCl$ to its aqueous solution?

In the group analysis of cations, $Ba^{2+}$ and $Ca^{2+}$ are precipitated respectively as

$A$ 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 cations does not give a precipitate with $H_2S$ in a neutral medium?

On passing $H_2S$ gas,a black precipitate of $II$ group is obtained. The mixture may not contain:

The reagent that can distinguish between silver and lead salt is