What color does lead acetate give with $H_2S$?

Which reagent can be used to identify nickel ion $(Ni^{2+})$?

Which mixture can be separated by a concentrated aqueous solution of sodium hydroxide $(NaOH)$?

Which of the following cations will give a precipitate with $Na_2C_2O_4$ solution in the presence of acetic acid?

Which of the following salts is insoluble in water at room temperature but soluble in boiling water?

Identify the metal $M$ and the precipitate $Z$ in the following reaction sequence:
$MSO_4$ $\xrightarrow{NH_4OH} \downarrow X \text{ (white)}$ $\xrightarrow{NH_4OH \text{ (excess)}} Y$ $\xrightarrow{H_2S} \downarrow Z$