• # question_answer A metal which is not affected by cone. ${{H}_{2}}S{{O}_{4}},HN{{O}_{3}}$ or alkalis forms a compound X. This compound X can be used to give a complex which finds its application for toning in photography? The metal is A)  $Au$                          B)  $Ag$C)  $Hg$                          D)  $Cu$

$Au,$ the gold is not attacked by acids and alkalis. It forms $AuC{{l}_{3}}$.$AuC{{l}_{3}}$ farther reacts with $HCl$ to form $H[Au{{(Cl)}_{4}}]$ which is used in photography. $AuC{{l}_{3}}+HCl\xrightarrow[{}]{}\underset{Complex}{\mathop{H[Au{{(Cl)}_{4}}]}}\,$