Question

Cinnabar ($HgS$) is a prominent ore of mercury. What is the percentage of mercury are present in 225 gms of pure $HgS$? (molar mass of $Hg$ and $S$ are $200.6gmmo{l}^{-1}$ and $32gmmo{l}^{-1}$ respectively)

• A. 194.04 gms
• B. 200.6 gms
• C. 320.4 gms
• D. 260.8 gms

Answer 1

Answer: (A)

194.04 gms

Molar mass of $HgS$ $=200.6+32=232.6gmmo{l}^{-1}$
Mass of $Hg$ in $232.6gms$ of $HgS=200.6gms$
Mass of $Hg$ in $225gm$ of $HgS$ $=\frac{200.6}{232.6}\times 225=194.04g$