Question

A metal $M$ which is not affected by strong acids like conc. $HN{O}_3,conc.H_{2}S{O}_4$ and conc. solution of alkalies like $NaOH,KOH$ forms $MC{l}_3$ which finds use for toning in photography. The metal $M$ is :

• A. $Ag$
• B. $Hg$
• C. $Au$
• D. $Cu$

Answer 1

Answer: (C)

$Au$

Gold and silver both find use for toning in photography. However $Au$ is not affected by strong acids and strong alkalies. $Au$ forms $AuC{l}_3$, whereas $Ag$ forms $AgCl$. Hence, metal M is $Au$.